essay questions about analogy

30 Writing Topics: Analogy

Ideas for a Paragraph, Essay, or Speech Developed With Analogies

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An analogy is a kind of comparison that explains the unknown in terms of the known, the unfamiliar in terms of the familiar.

A good analogy can help your readers understand a complicated subject or view a common experience in a new way. Analogies can be used with other methods of development to explain a process , define a concept, narrate an event, or describe a person or place.

Analogy isn't a single form of writing. Rather, it's a tool for thinking about a subject, as these brief examples demonstrate:

• "Do you ever feel that getting up in the morning is like pulling yourself out of quicksand? . . ." (Jean Betschart, In Control , 2001)
• "Sailing a ship through a storm is . . . a good analogy for the conditions inside an organization during turbulent times, since not only will there be the external turbulence to deal with, but internal turbulence as well . . ." (Peter Lorange, Leading in Turbulent Times , 2010)
• "For some people, reading a good book is like a Calgon bubble bath — it takes you away. . . ." (Kris Carr, Crazy Sexy Cancer Survivor , 2008)
• "Ants are so much like human beings as to be an embarrassment. They farm fungi, raise aphids as livestock, launch armies into wars, use chemical sprays to alarm and confuse enemies, capture slaves. . . ." (Lewis Thomas, "On Societies as Organisms," 1971)
• "To me, patching up a heart that'd had an attack was like changing out bald tires. They were worn and tired, just like an attack made the heart, but you couldn't just switch out one heart for another. . . ." (C. E. Murphy, Coyote Dreams , 2007)
• "Falling in love is like waking up with a cold — or more fittingly, like waking up with a fever. . . ." (William B. Irvine, On Desire , 2006)

British author Dorothy Sayers observed that analogous thinking is a key aspect of the writing process . A composition professor explains:

Analogy illustrates easily and to almost everyone how an "event" can become an "experience" through the adoption of what Miss [Dorothy] Sayers called an "as if" attitude. That is, by arbitrarily looking at an event in several different ways, "as if" if it were this sort of thing, a student can actually experience transformation from the inside. . . . The analogy functions both as a focus and a catalyst for "conversion" of event into experience. It also provides, in some instances not merely the To discover original analogies that can be explored in a paragraph , essay, or speech, apply the "as if" attitude to any one of the 30 topics listed below. In each case, ask yourself, "What is it like ?"

Thirty Topic Suggestions: Analogy

• Working at a fast-food restaurant
• Moving to a new neighborhood
• Starting a new job
• Quitting a job
• Watching an exciting movie
• Reading a good book
• Going into debt
• Getting out of debt
• Losing a close friend
• Leaving home for the first time
• Taking a difficult exam
• Making a speech
• Learning a new skill
• Gaining a new friend
• Responding to bad news
• Responding to good news
• Attending a new place of worship
• Dealing with success
• Dealing with failure
• Being in a car accident
• Falling in love
• Getting married
• Falling out of love
• Experiencing grief
• Experiencing joy
• Overcoming an addiction to drugs
• Watching a friend destroy himself (or herself)
• Getting up in the morning
• Resisting peer pressure
• Discovering a major in college
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What is an Analogy? Explained With 10 Top Examples

What is an analogy? Read our guide with top examples and in-depth explanations so you can wrap your head around this literary device.

Literary devices make your prose more colorful and vivid, allowing the reader to make associations. What is an analogy? An analogy compares two seemingly unlike things to help draw a conclusion by highlighting their similarities. Unlike other comparisons, like similes and metaphors, an analogy gives more detail about the comparison to help the reader understand it better. 

While there are many different types of analogy to study, the best way to understand this and other figures of speech is to consider examples. After reading a few analogies, you will be better equipped to spot them or write your own. And when you have finished here, check out our comparison article, simile vs metaphor .

What is An Analogy?

What are the benefits of using an analogy, analogy examples, 1. a name is a rose from romeo and juliet, 2. life is a shadow from macbeth, 3. the crowd is like a fisherman in “a hanging”, 4. life is like a box of chocolates from forrest gump, 5. pulling out troops is like salted peanuts from henry kissinger, 6. the futility of a new author from cocktail time, 7. the mystery of life in let me count the ways, 8. the push for freedom is like summer’s heat in “i have a dream”, 9. a needle in a haystack, 10. rearranging deck chairs on the titanic, 11. the matrix’s pill analogy, 12. harry potter and the sorcerer’s stone, what is the opposite of an analogy, what is an example of an analogy, what is the simple definition of analogy, what are 5 examples of analogy, what is another word for an analogy.

An analogy compares two concepts, usually to explain or clarify an idea. Writers use analogies to help people understand complex or abstract topics by relating something abstract to the familiar or concrete. They also use them as a type of literary device to improve the readability of their works.

By highlighting similarities, a writer helps readers see how one thing works or behaves by comparing the characteristics of abstract ideas to more familiar ideas. As a result, a concept or idea becomes easier to understand and even more memorable.

For example, a news reporter could employ this word analogy: “The presidential race for 2024 is like a chessboard…” Teachers use different types of analogies to demonstrate a concept to a student. For this reason, analogy tests often form part of standardized tests in any good English curriculum.

Analogies work in the real world too! For example, if a running coach wants to explain how a runner can run faster, they could use an analogy like “Pump your arms like a train” to help people understand how they should use their arms and legs to run faster. You might also be interested in learning  what is tautology .

Examples of analogies exist in classic literature, the latest books, movies and TV shows. Here are a few:

Often, analogies compare abstract concepts to something you can touch and feel. There are several examples of analogy in William Shakespeare’s Romeo and Juliet. In this analogy, the playwright compares someone’s name to a rose. The rose retains its sweet smell no matter how it is named, as does the person, regardless of his name. Read our guide to the best books of classic literature .

“If you want my final opinion on the mystery of life and all that, I can give it to you in a nutshell. The universe is like a safe to which there is a combination. But the combination is locked up in the safe.”

Life is a difficult concept to understand, making it a favorite topic for people who write analogies. In Act V of Macbeth, Shakespeare creates an analogy example by comparing a person’s life, and its brevity, to a fleeting shadow:

“Life’s but a walking shadow, a poor player That struts and frets his hour upon the stage And then is heard no more. It is a tale  Told by an idiot, full of sound and fury, Signifying nothing.”

Because life is so fleeting, this analogy works. The reader can see the shadow flitting about on the stage, then disappearing, reminding the reader how short life really is. You might also find these  headings and subheadings examples  helpful.

Some analogies take a little more time to explain yet still compare unlike things to make a point. For example, in his essay entitled  A Hanging  George Orwell describes the crowd gripping a man as they lead him to the gallows. The analogy is the comparison to the way a man would hold a slippery fish:

“They crowded very close about him, with their hands always on him in a careful, caressing grip, as though all the while feeling him to make sure he was there. It was like men handling a fish which is still alive and may jump back into the water. But he stood quite unresisting, yielding his arms limply to the ropes, as though he hardly noticed what was happening.”

This analogy is also an example of a simile because it uses the word “like” to make the comparison. However, because it extends beyond just one statement but has a complete description and explanation, it brings more imagery to the reader’s mind and thus is an analogy. Read our guide to the  best satirical authors .

Some analogies are short and sweet, rather than taking up an entire literary work. In the movie Forrest Gump, both the title character and his mother refer to life as a “box of chocolates.” In one of the most famous figures of speech from this movie, Forest says:

“My mom always said life was like a box of chocolates. You never know what you’re gonna get.”

Though this is a simple statement, it is an example of an analogy. The reader has probably experienced the feeling of grabbing chocolate and wondering what flavor it is, so this is a good analogy. But, like life, that box of chocolates always has the potential to give you the unexpected. You might also be wondering,  what is point of view?

Though technically a historian and not a literary genius, Henry Kissinger was famous for many of his analogies. One of his most commonly quoted is this:

“Withdrawal of U.S. troops will become like salted peanuts to the American public; the more U.S. troops come home, the more will be demanded. This could eventually result, in effect, in demands for unilateral withdrawal.”

This quote comes from a  memorandum Kissinger sent to President Nixon  regarding the conflict in Vietnam. He warned the president that bringing troops home a little at a time would create demand for more withdrawal, just like eating tasty peanuts makes you want to eat more. 

Writing a book is definitely challenging, especially when doing so for the first time. This fact is the source of one famous analogy in literature. In  Cocktail Time , P.G. Wodehouse compares a new author to someone performing an impossible task:

“It has been well said that an author who expects results from a first novel is in a position similar to that of a man who drops a rose petal down the Grand Canyon of Arizona and listens for the echo.”

Clearly, expecting to hear an echo from a rose petal at the Grand Canyon is foolishness. Thus, based on this analogy, the logical argument that expecting to see significant returns from a first novel is also foolish. You might also be wondering  what is a split infinitive .

In his novel  Let Me Count the Ways , Dutch author and journalist  Peter De Vries  compares life and a safe. He writes:

In this analogy, the safe can’t be unlocked. Similarly, the mystery of life is something people can’t fully understand.

Speechwriters who are good at their jobs often use analogies to make their words more memorable. In his famous speech, “I Have a Dream,” Martin Luther King, Jr., makes an analogy between the anger of African-Americans and the heat of summer in this quote:

“This sweltering summer of the Negro’s legitimate discontent will not pass until there is an invigorating autumn of freedom and equality.”

Just like the heat of summer is unquenchable, the frustration of those facing endless prejudice cannot be quenched. Yet when freedom comes, it is like the relief of the cool autumn breeze. This quote is still used today when people remember the famous civil rights activist.

Finding a needle in a haystack is a nearly impossible task. This catchphrase or analogy example is often applied to tasks that seem out of reach. For instance, one common analogy says:

“Finding a good man is as easy as finding a needle in a haystack.”

This analogy indicates it is nearly impossible to find a “good man.” Though unfair to the male gender, it does make its point through the use of analogy. Most people can picture digging through the hay to find a needle, but to no avail, which makes the analogy work.

This analogy does not come from any famous literary work or speech but from a well-known historical moment. The sinking of the Titanic was one such event. Sometimes people, when talking about something futile, will say:

“That’s as useful as rearranging deck chairs on the Titanic.”

Since the Titanic was a doomed vessel, the futility of the effort is seen in this use of figurative language. The phrase can apply to any effort that would not matter because the result is a failure, like the sinking of the infamous ship. Check out our metonymy examples .

In The Matrix , there is a famous scene where Morpheus presents the red pill/blue pill analogy to Neo. The analogy is a turning point in the movie where Neo has to pick which path he wants to go down. The red pill represents embracing the uncomfortable truth and becoming aware of the real world he lives in. The blue pill represents choosing the familiar and comfortable path where he can remain in his world, oblivious to the dark reality he suspects.

“You take the blue pill, the story ends. You wake up in your bed and believe whatever you want to believe. You take the red pill, you stay in Wonderland, and I show you how deep the rabbit hole goes.”

J.K. Rowling uses analogies throughout her works, often to give insight into the minds and personalities of the characters. In Harry Potter and the Sorcerer’s Stone , Professor Dumbledore speaks to Harry and imparts some of his famous wisdom.

“It does not do to dwell on dreams and forget to live.”

In this analogy example sentence, he suggests that while having dreams and aspirations are important, it’s just as important to be grounded and present in the current moment. The analogy aims to show Harry that he should balance his ambition and reality and become mindful in the midst of the chaos that he lives in. It also encourages Harry to let go of regrets and become fully present in his life as it is today.

An antithesis highlights the differences between two contrasting ideas. For example, the analogy “Man plans, and God laughs” shows how we can strive and work towards a goal, only for God or fate to intervene and uproot our best plans. For further reading on a similar subject, check out our post on examples of metaphors in literature .

FAQs About What is an Analogy

An example of an analogy is “Hope is the lighthouse that stands tall amidst the stormy seas of despair.” The analogy emphasizes the idea that hope can help us navigate through the storms of life, guiding us toward a better future and helping us persevere in the face of challenges.

An analogy is a comparison between two things that are alike in some way, often used to help explain something or make it easier to understand.

1. Her laughter was music to his ears. 2. Time is money. 3. He is a shining star in the world of science. 4. The classroom was a zoo during the group activity. 5. Life is a journey with its share of twists and turns.

A related term for analogy is comparison. A comparison is a way of describing the similarities or differences between two things in order to better understand them.

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• Literary Terms
• Definition & Examples
• When & How to write an Analogy

I. What is an Analogy?

An analogy is a literary technique in which two unrelated objects are compared for their shared qualities. Unlike a simile or a metaphor, an analogy is not a figure of speech, though the three are often quite similar. Instead, analogies are strong rhetorical devices used to make rational arguments and support ideas by showing connections and comparisons between dissimilar things.

II. Examples of Analogy

Analogies are commonly used to show important comparisons and make solid arguments. Here are some examples:

Every choice you make is like spinning the wheel of fortune—sometimes you will get the result that you desire, while other times you will end up with something you always hoped to avoid.

Raising children requires the same dedication you would give to a garden. Nurture them, feed them, introduce them to both light and dark, and have patience; and soon you will see them grow into blooming wonders.

In the first example, the writer could have said “Every choice has a different consequence.” But like similes, analogies make associations between things that wouldn’t usually be compared (like choices to wheels of fortune and children to gardens). These comparisons create better descriptions and sensory images in the minds of readers. On the other hand, analogies are more elaborate and informational than similes or metaphors , providing support for the comparisons made rather than just stating them as simple truths. As you can see, the second example explains how children and gardens have similar qualities because they require similar growing conditions.

Photosynthesis does for plants what digesting food does for animals. It is the process that lets them convert nutrients into the fuel needed to grow and develop. 

You may also see analogies that compare relationships rather than individual things. But the analogy still works in the same way; it explains how the relationships share a similar quality of transforming nutrients.

III. Types of Analogy

A. literal analogy.

In a literal analogy, you are saying that one thing really is similar to another. This is the kind of analogy that you would draw if you wanted to make an argument  or persuasion. For example, when scientists test a new medicine on laboratory mice, they are arguing that mice and humans really are similar in medically significant ways. Therefore, as the argument goes, if a medicine works on mice, it should also work on humans (or at least it’s ready for human testing).

b. Figurative Analogy

In a figurative analogy, you’re simply drawing a comparison between two unrelated things to highlight a certain characteristic; you’re not necessarily saying that the things are truly similar .  Take, for example, the wheel of fortune example. If life were truly similar to a wheel of fortune you would have a lot less control over our choices and the consequences would be unpredictable.

IV. The Importance of Analogy

As mentioned, analogies are used to make logical arguments and comparisons. Here are a few ways writers might use analogies:

a. Make abstract ideas more concrete

There are some people – like teachers, professors, and technical writers – who explain difficult ideas for a living. It’s a tough job! One way to make it easier is to draw analogies to things your readers or students are already familiar with. For example, a biology teacher might explain the immune system by saying, “What policemen do in a town, white blood cells do inside the body.”

b. Add depth and feeling to an image

Consider this example:

 She felt like a raft floating in the middle of an dark, endless ocean. Like her, the raft was was floating along, alone, worn out, and unable to reach a steady place in which to settle.

Notice what a powerful image this descriptions brings to mind. Without the analogy, the author would just be saying “She was lonely and exhausted.” How boring! The analogy makes her emotions seem dark and overwhelming – just as the ocean at night.

c. Making a persuasive argument

Obviously, this is rare in poetry and fiction, where making an argument isn’t the point. But in essays , literary analysis, and many other fields, persuasion is the name of the game – and analogy can be a powerful tool for that purpose. It’s especially useful when you want to show the flawed reasoning in another person’s argument:

Person A : Lots of history’s dictators started as soldiers; therefore, soldiers should never become politicians because they’ll end up as dictators.

Person B : But that doesn’t make sense! It’s like saying “lots of alcoholics started out by drinking milk; therefore no one should ever drink milk.” Just as there are many milk-drinkers who don’t become alcoholics, there are also many soldiers who don’t become dictators .

Notice how Person B has employed a clever analogy to show that Person A is making a faulty argument.

V. Examples of Analogy in Literature

They crowded very close about him, with their hands always on him in a careful, caressing grip, as though all the while feeling him to make sure he was there. It was like men handling a fish which is still alive and may jump back into the water. (George Orwell, A Hanging)

In this passage, Orwell is describing the crowd’s reaction to seeing a man hanged. One interpretation of the analogies is that they create a supernatural feeling by subtly suggesting the possibility that the dead man may simply disappear, or may suddenly come back to life.

What gunpowder did for war the printing press has done for the mind. (Wendell Phillips, Public Opinion on the Abolition Question)

Gunpowder revolutionized war and brought down old hierarchies and strategies – after the introduction of the gun, war would never be the same. Similarly, the invention of the printing press allowed books and newspapers to reach vast audiences that otherwise had no access to the written word. This revolutionized education and made possible an era of widespread literacy and democratic thought.

“Evolution is a blind giant who rolls a snowball down a hill. The ball is made of flakes—circumstances. They contribute to the mass without knowing it. They adhere without intention, and without foreseeing what is to result. When they see the result they marvel at the monster ball and wonder how the contriving of it came to be originally thought out and planned. Whereas there was no such planning, there was only a law: the ball once started, all the circumstances that happened to lie in its path would help to build it, in spite of themselves.” (Mark Twain, Tales of Wonder)

Here, Twain uses an analogy to speak about evolution, comparing it to a giant rolling a snowball down the hill–the results are quite unpredictable, but inevitable.

VI. Examples of Analogy in Pop Culture

(adsbygoogle = window.adsbygoogle || []).push({}); “My momma always said “life is like a box of chocolates – you never know what you’re gonna get!” (Forrest Gump)

Here, Forrest Gump shares a very memorable analogy, beginning with the simile “life was like a box of chocolates.” But, this is an analogy because it gives further support and explanation for the comparison, showing that life has many choices and surprises, just like a box of chocolate.

Oh, he ‘loved to laugh?’ Well, that doesn’t tell you anything! That’s like saying , ‘He hungered for food! (Patton Oswald, Obituaries)

This is a humorous version of argument by analogy. Oswald, a standup comedian, is poking fun at articles about him by comparing that statement to something obviously commonplace, showing that the argument that he “loved to laugh” is about as strong as saying he gets hungry for food.

People are like stained-glass windows. They sparkle and shine when the sun is out, but when the darkness sets in, their true beauty is revealed only if there is a light from within. (Quote by Elisabeth Kübler-Ross in The Leader’s Digest by Jim Clemmer, 2003)

In this quote, the groundbreaking psychiatrist Elizabeth Kübler-Ross (well-known for her 5 Stages of Grief) gives an analogy about the human condition, saying that people, like stained-glass, work differently in situations of light and dark.

VII. Related Terms

People often confuse analogies with similes and metaphors, which are both figures of speech. However, they are actually very different, specifically because an analogy is a rhetorical device, not a figure of speech. While similes and metaphors are generally quite short and simple, analogies are more elaborate and explanatory, because they support arguments.

A  figure of speech that makes comparisons using explicit “comparing” words such as like or as. So when you see like or as underlined in this article, you know it’s an example of a simile.

“What light through yonder window breaks? It is the East, and Juliet is like the sun!”

“…It is the East, and Juliet is as radiant as the sun!”

A figure of speech where unrelated things are compared – basically, it’s just a simile with the “like” or “as” removed.

“What light through yonder window breaks? It is the East, and Juliet is the sun!” (William Shakespeare, Romeo and Juliet)

It’s important to remember that a metaphor is not a kind of analogy – it’s a different figure of speech altogether. However, it’s very similar to analogy in that they both depend on some kind of similarity between two different objects.

Example of an analogy versus simile and metaphor:

Simile : Life is like a garden.

Metaphor : Life is a garden.

Analogy: Life is just like a garden–it is ever growing and changing, needing care and dedication, and always filled with beautiful surprises.

Again, it’s important to remember that metaphors and similes are figures of speech, while analogies are NOT. However, they are very similar to analogies in that they both depend on some kind of similarity between two different objects.

List of Terms

• Alliteration
• Amplification
• Anachronism
• Anthropomorphism
• Antonomasia
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• Autobiography
• Bildungsroman
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• Extended Metaphor
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• Intertextuality
• Juxtaposition
• Literary Device
• Malapropism
• Onomatopoeia
• Parallelism
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• Point of View
• Polysyndeton
• Protagonist
• Red Herring
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Analogy: Definition & Meaning (with Examples)

Analogy is one of the most common types of literary devices. It's also one of the hardest to understand because it's similar to other types of figurative language. Today, we're going to dive into the meaning of analogy with in-depth explanations and examples.

Analogy Definition: What Is an Analogy?

Let's start with the dictionary definition of an analogy. According to Merriam-Webster, an analogy is "a comparison of two otherwise unlike things based on a resemblance of a particular aspect."

We use analogies all the time in speaking and fields like history and science. They help us illustrate a point that might be hard to comprehend. For example, we might make an analogy between the Trail of Tears of U.S. History and the Jewish Diaspora of World History. In biology, you might discuss the analogous relationship of bat wings and bird wings.

As a literary device, however, analogy's meaning has more nuance that separates it from other types of rhetorical devices. Let's look at the literary meaning of analogy in more detail in the next section.

Analogy Meaning

As a rhetorical device, analogy compares two unlike things with the purpose of both illustrating a comparison and explaining it. You aren't just trying to show a similarity when you use an analogy. You are also trying to make a point about this similarity.

Analogies can be useful to explain complex concepts by comparing them to a familiar idea. Analogies also help paint a picture in a reader's mind and add emphasis to important ideas in writing.

Let's take a look at a popular example of an analogy from the movie Forrest Gump . In the movie, Forrest says that his mother always told him, "Life is like a box of chocolates—you never know what you're gonna get."

If Forrest just said that life was like a box of chocolates, we would wonder what the similarity is. What point is he trying to get across? It might be that life is sweet or that life is a gift from someone who loves you. But then he explains that we never know where life will take us or what circumstances we will fall into. We don't know until we get there; we can't see the future.

He's not just painting a picture about life. He's making a point about the uncertainty of life and the many twists and turns it takes. This analogy goes further and illustrates the entire premise of the film. Forrest goes from being a boy in leg braces to an international ping pong champion to a dad. No one could have predicted that!

Analogies look similar to other types of figurative language. So, what's the difference?

Analogy vs. Metaphor

A metaphor is a figure of speech that shows a likeness between two otherwise different things. The point of a metaphor is comparison. For example, we can say, "the kids were a bunch of monkeys today." We are comparing kids to monkeys.

An analogy not only compares but explains. "The kids were a bunch of monkeys today, climbing all over the furniture, running all over the house, and shrieking."

As you can see, an analogy might feature a metaphor, but it goes further in making a point. This is also different from an extended metaphor. An extended metaphor continues to use a comparison to illustrate similarities of two objects. An analogy requires some explicit explanation to make its point.

Analogy vs. Simile

A simile is a type of metaphor, but it uses "like" or "as" to draw comparisons. Just like with a metaphor, an analogy might use a simile to compare two things, but then the analogy goes on to explain the idea behind it.

The Forrest Gump quote is an example of this. The part of the quote, "Life is like a box of chocolates," is a simile. The next part of the quote that tells how life and a box of chocolates are related is what makes this quote an analogy.

Many analogies use similes and metaphors to make comparisons, but it is not required.

Analogy vs. Allusion

Another figurative language element that is easy to confuse with analogy is allusion.

Allusion is a mention of a person, place, or thing that is considered common knowledge. It's often a reference to a famous person or event or a well-known story, like fairy tales, myths, or religious parables.

Allusion is a way to compare two things. Let's look at an example:

• "The books on the top shelf were forbidden fruit."

Forbidden fruit refers to the fruit of the Tree of Knowledge in the Bible. This is an allusion. We can draw enough conclusions from this allusion to understand what the books represent.

Allusions can be part of analogies, too. Remember, where allusions compare, analogies explain:

• "If the library was Eden, the books on the top shelf were forbidden fruit. They opened my eyes to a world beyond the life I had always known."

All of these are useful types of figurative language. The difference lies in the purpose. If the goal is to explain an idea or get a specific point across, it's an analogy.

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Analogies, Idioms, and Clichés

Sometimes analogies become so well-known that they become part of our everyday lexicon. Idioms are phrases that don't make sense literally, but they do make sense figuratively. Overused idioms can become clichés.

An example of an analogy that is a cliché is "she's as blind as a bat." It's a very overused comparison. Use ProWritingAid's Clichés Report to help identify the clichés and idioms in your writing. While some common analogies might help you get your point across, some can actually hinder your writing's clarity, especially to non-native speakers.

Try the Cliché Report with a free ProWritingAid account.

Analogy Examples

You probably hear or read analogy examples all the time—they're a common rhetorical device. Today, we'll take a look at some analogy examples from everyday sentences and literature.

Examples of Analogy in a Sentence

Humans love figurative language, and we create analogies in our everyday speech. Here are some examples.

• Ordering clothes online is like playing the lottery. Some fit great, and some are a complete waste of money when they don't even go over your head!
• His voice was warm honey on toast, sweet and comforting and familiar.
• She thought the sound of babies crying was as annoying as fingernails on a chalkboard. Babies definitely weren't for her.

Can you create any analogies?

Examples of Analogy in Literature

Analogy is a powerful rhetorical device. Here are some famous examples of analogy in literature:

• "All the world’s a stage / And all the men and women merely players / They have their exits and their entrances / And one man in his time plays many parts / His acts being seven ages."— As You Like It , William Shakespeare
• “I can admire the perfect murderer—I can also admire a tiger—that splendid tawny-striped beast. But I will admire him from outside his cage. I will not go inside . . . . That is to say, not unless it is my duty to do so. For you see, Mr. Shaitana, the tiger might spring . . . .”— Cards on the Table , Agatha Christie
• "Memory is to love what the saucer is to the cup."— The House in Paris , Elizabeth Bowen

Tips on How to Write an Analogy

When you're writing an analogy to express an idea, it's important to keep two things in mind. First, make sure that at least one of the two things you're comparing is familiar and easy to understand. An analogy should make your point clear to the reader, not leave them confused! Animal or nature imagery, allusions to well-known tales, and everyday objects are good things to use in your analogies.

Secondly, make sure that your comparison is clear without much explanation. If you compare a shy, demure princess to a tiger, you need to explain what specific aspects of the princess and the tiger are similar. Is she ferocious when her loved ones are attacked? Does she prefer to spend time alone outdoors and seethe when caged?

If it takes too many sentences to explain the analogy, try using different imagery that is simpler to understand.

Different Types of Analogy

There are two main types of analogy. These are based on how closely related the two things being compared are.

Literal Analogy

The first type of analogy is a literal analogy. When two things are very closely related, we compare them with literal analogies. These are the types of analogies commonly used in science. Literal analogies can help scientists draw comparisons or make a logical argument.

For example, a virologist might compare the viral structure of two different viruses. If the virus has a similar structure and similar symptoms to another, they are analogous. This will help them theorize that the second virus can be treated similarly to the first.

Literal analogies don't have to be just for science! If you're a baker, you might know that you can make a cheesecake out of either cream cheese or mascarpone. As an analogy, we can say that mascarpone is a lot like cream cheese. They both have high fat content, are very soft, and are not aged.

Literal analogies are the type you might see on standardized tests. They used to feature on the SAT and looked like this: A:B::C:D. You can read literal analogies as "A is to B as C is to D."

Here's a simple example:

• Night is to sleep as morning is to wake .

Standardized tests would have one or more of the words blank, and you had to determine the connection in the analogy. How are they connected?

Figurative Analogy

A figurative analogy makes a comparison between two or more things that aren't necessarily that similar at first glance. The analogy focuses on making a comparison based on a specific aspect of the unrelated things. This is called shared abstraction .

Take a look at the following analogy:

• "Giving candy and coffee as appreciation gifts is just rearranging deck chairs on the Titanic. It's not actually fixing the issues that are causing low morale, like low pay, long hours, and micromanaging."

If the Titanic is sinking, it's pointless to rearrange deck chairs. Likewise, this quote suggests spending money on little gifts is pointless because it's not addressing the real issues at hand that are causing employee dissatisfaction.

No one is suggesting that low morale at a company is the same thing as the hundreds of lives lost on the Titanic. The shared abstraction is doing something pointless in the face of a disaster.

Should You Use Analogies in Your Writing?

Analogies are powerful literary devices because they create an image in the reader's mind while making a point in a deeper way than a metaphor. Remember, an analogy compares two objects with the purpose of explaining a deeper idea. A literal analogy compares two very similar objects, while a figurative analogy relies on shared abstractions.

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Metaphors and Analogies: How to Use Them in Your Academic Life

Certain Experiences in life can't be captured in simple words. Especially if you are a writer trying to connect with your audience, you will need special threads to evoke exact feelings.

There are many literary devices to spark the readers' imagination, and analogies and metaphors are one of that magical arsenal. They enrich your text and give it the exact depth it will need to increase your readers' heartbeat.

Taking a particular characteristic and associating it with the other not only enriches your text's linguistic quality but gives the reader a correct pathway to deeper layers of a writer's psyche.

In this article, we are going to take a good look at the difference between analogy and metaphor and how to use them in your academic writing, and you will find some of the most powerful examples for each. Learn more about this and other vital linguistic tools on our essay writer service website.

What are Metaphors: Understanding the Concept

Let's discuss the metaphors definition. Metaphors are a figure of speech that compares two unrelated concepts or ideas to create a deeper and more profound meaning. They are a powerful tool in academic writing to express abstract concepts using different analogies, which can improve the reader's understanding of complex topics. Metaphors enable writers to paint vivid pictures in the reader's mind by comparing something familiar with an abstract concept that is harder to grasp.

The following are some of the most famous metaphors and their meanings:

• The world is your oyster - the world is full of opportunities just waiting for you to grab them
• Time is money - time is a valuable commodity that must be spent wisely
• A heart of stone - someone who is emotionally cold and unfeeling

Analogies Meaning: Mastering the Essence

Analogies, on the other hand, are a comparison of two concepts or ideas that have some similarity in their features. They are used to clarify complex ideas or to make a new concept more relatable by comparing it to something that is already familiar.

Analogies are often followed by an explanation of how the two concepts are similar, which helps the reader to understand and make connections between seemingly disparate ideas. For example, in academic writing, if you were explaining the function of a cell membrane, you might use an analogy, such as comparing it to a security gate that regulates what enters and exits a building.

Check out these famous analogies examples:

• Knowledge is like a garden: if it is not cultivated, it cannot be harvested.
• Teaching a child without education is like building a house without a foundation.
• A good friend is like a four-leaf clover; hard to find and lucky to have.

Benefits of Metaphors and Analogies in Writing

Chances are you are wondering why we use analogies and metaphors in academic writing anyway?

The reason why metaphors are beneficial to writers, especially in the academic field, is that they offer an effective approach to clarifying intricate concepts and enriching comprehension by linking them to more familiar ideas. Through the use of relatable frames of reference, these figures of speech help authors communicate complicated notions in an appealing and comprehensible way.

Additionally, analogies and metaphors are a way of artistic expression. They bring creativity and imagination to your writing, making it engaging and memorable for your readers. Beautiful words connect with readers on a deeper emotional level, allowing them to better retain and appreciate the information being presented. Such linguistic devices allow readers to open doors for imagination and create visual images in their minds, creating a more individualized experience.

However, one must be mindful not to plagiarize famous analogies and always use original ideas or appropriately cite sources when necessary. Overall, metaphors and analogies add depth and beauty to write-ups, making them memorable for years to come.

Understanding the Difference Between Analogy and Metaphor

While metaphors and analogies serve the similar purpose of clarifying otherwise complex ideas, they are not quite the same. Follow the article and learn how they differ from each other.

One way to differentiate between analogies and metaphors is through the use of 'as' and 'like.' Analogies make an explicit comparison using these words, while metaphors imply a comparison without any overt indication.

There is an obvious difference between their structure. An analogy has two parts; the primary subject, which is unfamiliar, and a secondary subject which is familiar to the reader. For example, 'Life is like a box of chocolates.' The two subjects are compared, highlighting their similarities in order to explain an entire concept.

On the other hand, a metaphor describes an object or idea by referring to something else that is not literally applicable but shares some common features. For example, 'He drowned in a sea of grief.'

The structural difference also defines the difference in their usage. Analogies are often used in academic writing where hard concepts need to be aligned with an easier and more familiar concept. This assists the reader in comprehending complex ideas more effortlessly. Metaphors, on the other hand, are more often used in creative writing or literature. They bring depth and nuance to language, allowing for abstract ideas to be communicated in a more engaging and imaginative way.

Keep reading and discover examples of metaphors and analogies in both academic and creative writing. While you are at it, our expert writers are ready to provide custom essays and papers which incorporate these literary devices in a seamless and effective way.

Using Famous Analogies Can Raise Plagiarism Concerns!

To avoid the trouble, use our online plagiarism checker and be sure that your work is original before submitting it.

Analogies and Metaphors Examples

There were a few analogies and metaphors examples mentioned along the way, but let's explore a few more to truly understand their power. Below you will find the list of metaphors and analogies, and you will never mistake one for the other again.

• Love is like a rose, beautiful but with thorns.
• The human body is like a machine, with many intricate parts working together in harmony.
• The structure of an atom is similar to a miniature solar system, with electrons orbiting around the nucleus.
• A computer's motherboard is like a city's central system, coordinating and communicating all functions.
• The brain is like a muscle that needs constant exercise to function at its best.
• Studying for exams is like training for a marathon; it requires endurance and preparation.
• Explaining a complex scientific concept is like explaining a foreign language to someone who doesn't speak it.
• A successful team is like a well-oiled machine, with each member playing a crucial role.
• Learning a new skill is like planting a seed; it requires nurturing and patience to see growth.
• Navigating through life is like sailing a ship with unpredictable currents and changing winds.
• Life is a journey with many twists and turns along the way
• The world's a stage, and we are all mere players.
• Her eyes were pools of sorrow, reflecting the pain she felt.
• Time is a thief, stealing away moments we can never recapture.
• Love is a flame, burning brightly but at risk of being extinguished.
• His words were daggers piercing through my heart.
• She had a heart of stone, unable to feel empathy or compassion.
• The city was a jungle, teeming with life and activity.
• Hope is a beacon, guiding us through the darkest of times.
• His anger was a volcano, ready to erupt at any moment.

How to Use Metaphors and Analogies in Writing: Helpful Tips

If you want your readers to have a memorable and engaging experience, you should give them some level of autonomy within your own text. Metaphors and analogies are powerful tools to let your audience do their personal interpretation and logical conclusion while still guiding them in the right direction.

First, learn about your audience and their level of familiarity with the topic you're writing about. Incorporate metaphors and analogies with familiar references. Remember, literary devices should cleverly explain complex concepts. To achieve the goal, remain coherent with the theme of the paper. But be careful not to overuse metaphors or analogies, as too much of a good thing can make your writing feel overloaded.

Use figurative language to evoke visual imagery and breathe life into your paper. Multiple metaphors can turn your paper into a movie. Visualizing ideas will help readers better understand and retain the information.

In conclusion, anytime is a great time to extend your text's impact by adding a well-chosen metaphor or analogy. But perfection is on the border of good and bad, so keep in mind to remain coherent with the theme and not overuse any literary device.

Metaphors: Unveiling Their Cultural Significance

Metaphors are not limited to just academic writing but can also be found in various forms of culture, such as art, music, film, and television. Metaphors have been a popular element in creative expression for centuries and continue to play a significant role in modern-day culture. For instance, metaphors can help artists convey complex emotions through their music or paintings.

Metaphors are often like time capsules, reflecting the cultural and societal values of a particular era. They shelter the prevailing beliefs, ideals, and philosophies of their time - from the pharaohs of ancient Egypt to modern-day pop culture.

Metaphors often frame our perception of the world and can shape our understanding of our surroundings. Certain words can take on new meanings when used metaphorically in certain cultural contexts and can assimilate to the phenomenon it is often compared to.

Here you can find a list of literature and poems with metaphors:

• William Shakespeare loved using metaphors, and here's one from his infamous Macbeth: 'It is a tale told by an idiot, full of sound and fury, signifying nothing.'
• Victor Hugo offers a timeless metaphor in Les Misérables: 'She is a rose, delicate and beautiful, but with thorns to protect her.'
• Robert Frost reminds us of his genius in the poem The Road Not Traveled: 'The road less traveled.'

Movies also contain a wide range of English metaphors:

• A famous metaphor from Toy Story: 'There's a snake in my boot!'
• A metaphor from the famous movie Silver Lining Playbook: 'Life is a game, and true love is a trophy.'
• An all-encompassing and iconic metaphor from the movie Star Wars: 'Fear is the path to the dark side.'

Don't forget about famous songs with beautiful metaphors!

• Bob Dylan's Blowin' in the Wind uses a powerful metaphor when he asks: 'How many roads must a man walk down?'
• A metaphor from Johnny Cash's song Ring of Fire: 'Love is a burning thing, and it makes a fiery ring.'
• Bonnie Tyler's famous lyrics from Total Eclipse of the Heart make a great metaphor: 'Love is a mystery, everyone must stand alone.'

Keep reading the article to find out how to write an essay with the effective use of metaphors in academic writing.

Exploring Types of Metaphors

There is a wide variety of metaphors used in academic writing, literature, music, and film. Different types of metaphors can be used to convey different meanings and create a specific impact or evoke a vivid image.

Some common types of metaphors include similes / simple metaphors, implicit metaphors, explicit metaphors, extended metaphors, mixed metaphors, and dead metaphors. Let's take a closer look at some of these types.

Simple metaphors or similes highlight the similarity between two things using 'like' or 'as.' For example, 'Her eyes were as bright as the stars.'

Implicit metaphors do not make a direct comparison. Instead, they imply the similarity between the two concepts. An example of an implicit metaphor is 'Her words cut deep,' where the similarity between words and a knife is implied. Good metaphors are often implicit since they require the reader to use their own understanding and imagination to understand the comparison being made.

Explicit metaphors are straightforward, making a clear comparison between two things. For instance, 'He is a shining star.'

An extended metaphor, on the other hand, stretches the comparison throughout an entire literary work or section of a text. This type of metaphor allows the writer to create a more complex and elaborate comparison, enhancing the reader's understanding of the subject.

Mixed metaphors combine two or more unrelated metaphors, often leading to confusion and lack of clarity. If you are not an expert on the subject, try to avoid using confusing literary devices.

Dead metaphors are another danger. These are metaphors that have been overused to the extent that they have lost their original impact, becoming clichés and not being able to evoke original visual images.

In academic writing, metaphors create a powerful impact on the reader, adding color and depth to everyday language. However, they need to be well-placed and intentional. Using an inappropriate or irrelevant metaphor may confuse readers and distract them from the main message. If you want to avoid trouble, pay for essay writing service that can help you use metaphors effectively in your academic writing.

Exploring Types of Analogies

Like metaphors, analogies are divided into several categories. Some of the common types include literal analogies, figurative analogies, descriptive analogies, causal analogies, and false/dubious analogies. In academic writing, analogies are useful for explaining complex ideas or phenomena in a way that is easy to understand.

Literal analogies are direct comparisons of two things with similar characteristics or features. For instance, 'The brain is like a computer.'

Figurative analogies, on the other hand, compare two unrelated things to highlight a particular characteristic. For example, 'The mind is a garden that needs to be tended.'

Descriptive analogies focus on the detailed similarities between two things, even if they are not immediately apparent. For example, 'The relationship between a supervisor and an employee is like that of a coach and a player, where the coach guides the player to perform at their best.'

Causal analogies are used to explain the relationship between a cause and an effect. For instance, 'The increase in global temperatures is like a fever caused by environmental pollution.'

Finally, false/dubious analogies are comparisons that suggest a similarity between two things that actually have little in common. For example, 'Getting a college degree is like winning the lottery.'

If you are trying to explain a foreign concept to an audience that may not be familiar with it, analogies can help create a bridge and make the concept more relatable. However, coming up with a perfect analogy takes a lot of time. If you are looking for ways on how to write an essay fast , explore our blog and learn even more.

If you want your academic papers to stand out and be engaging for the reader, using metaphors and analogies can be a powerful tool. Now that you know the difference between analogy and metaphor, you can use them wisely to create a bridge between complex ideas and your audience.

Explore our blog for more information on different writing techniques, and check out our essay writing service for more help on crafting the perfect papers.

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Literary Devices

Last updated on: Jun 4, 2023

A Comprehensive Guide to Analogy In Literary Comparisons

By: Barbara P.

Reviewed By: Caleb S.

Published on: May 23, 2023

Sometimes, while reading a book, you feel words painting vivid pictures in your mind. Ever wondered how authors create such captivating stories? The secret lies in analogies. 

Analogies are like special codes in the literature that help us understand and feel things in a new way. But they can be tricky to decode or even add to your own writing.

That’s what this guide is here to help you with. In this blog, we'll discover all about analogies in literature. We'll learn how they work, explore different types, and discover how they make stories come alive. 

So, read on to sharpen your analysis and brighten your writing!

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Understanding Analogy

An analogy is a literary device that helps to explain or clarify something by comparing it to something else. It acts as a bridge , connecting two different ideas or concepts. 

By using an analogy, writers take something familiar and use it to describe something more complex or abstract, making it easier for readers to understand.

For example, in George Orwell's novel "Animal Farm," the animals on the farm represent the political figures of the Russian Revolution. This analogy helps readers grasp the complex political dynamics by comparing them to simpler animal characters.

Need to know more about other literary devices? Have a read here to learn about a number of literary devices !

Distinction between Simile, Metaphor, and Analogy

While similes, metaphors, and analogies are forms of comparison, they have slight differences in their usage. 

An analogy compares two things to help us understand or explain something. It connects unfamiliar ideas with familiar concepts. 

Similes use " like " or " as " to compare things directly, while metaphors state that one thing is another . 

In this quote, we see the use of simile , analogy , and metaphor :

Here is a quick review of the differences between the three literary devices:

Why Use Analogies in Literature

Analogies serve important purposes in literature, enhancing the overall reading experience. 

Let's explore why authors use analogies:

• Enhancing Understanding: Analogies make complex ideas more understandable by comparing them to something familiar, providing clarity and insight.
• Creating Vivid Imagery: They add depth and richness to descriptions, painting vivid pictures in readers' minds and bringing the narrative to life.
• Engaging Readers Emotionally: They evoke emotions and establish an emotional connection between the reader and the story, making it more captivating and memorable.
• Making Complex Ideas Accessible: Analogies simplify complex ideas, making them more accessible to a wider audience and expanding understanding.
• Stimulating Critical Thinking: They encourage critical thinking, prompting readers to draw connections, analyze patterns, and interpret underlying messages and themes.
• Enhancing Creativity: They offer a creative outlet for authors to express their ideas in unique and imaginative ways, captivating readers' attention.

Using analogies skillfully can really add richness to your text, so read on to learn how you can use them.

How to Use Analogies

Analogies are valuable tools that can be used in various situations to enhance understanding and communication. 

Here are some rules and tips to effectively use analogies:

Know Your Audience

Understand the knowledge, experiences, and background of your audience. Use analogies that resonate with them and align with their understanding.

Keep it Relevant

Ensure that your analogy is directly related to the topic or concept you're discussing. Avoid using analogies that are too far-fetched or unrelated, as they may confuse or distract your audience.

Use Simple and Familiar Comparisons

Choose analogies that are easy to understand and familiar to your audience. Everyday objects, common situations, or widely recognized phenomena work well to create relatable connections .

Highlight Key Similarities

Focus on the shared characteristics or behaviors between the analogy and the concept you're explaining. Emphasize the relevant aspects that help your audience grasp the intended meaning.

Make it Visual

Use descriptive language and vivid imagery to paint a clear picture in your audience's minds. Engage their senses by incorporating sensory details that enhance the visual representation of the analogy.

Provide Context

Set the stage by providing a brief context or explanation before presenting the analogy. This helps your audience connect the dots and understand how the analogy relates to the concept you're discussing.

Use Analogies Sparingly

While analogies can be powerful, avoid overusing them . Use them strategically to emphasize key points or to clarify complex ideas, but don't rely on them excessively.

How to Look for and Analyze Analogies

Works of literature are full of analogies. They add depth and meaning, forging connections between different elements.

Here are the steps to identify and analyze analogies in literary works:

• Pay attention to comparisons: Be on the lookout for instances where the author compares one thing to another. These comparisons can be indirect, drawing parallels between different elements in the text.
• Notice patterns and repeated imagery: Look for recurring symbols or images throughout the text. These can often indicate the presence of analogies and provide insights into the author's intended meaning.
• Consider thematic elements: Analyze the central themes and ideas explored in the literature. Analogies are often used to reinforce themes, so identifying the main themes can help in recognizing analogical connections.
• Engage with the text: Actively engage by asking questions and making connections. Look for similarities, parallels, or shared characteristics between different elements within the text.

Now, that you’ve learned how to identify analogies, here’s how you can analyze their role in the text:

• Identify shared characteristics: Once you've identified an analogy, focus on the elements being compared and find the similar qualities between them. This will help you understand the purpose of the analogy and its intended meaning.
• Consider the context: Analyze the surrounding context and the overall narrative of the literature. The analogy should fit within the broader storyline and contribute to the themes and messages conveyed by the author.
• Reflect on emotional impact: Consider the emotional impact of the analogy on the reader. How does it make you feel? What emotions does it evoke? This can provide insights into the intended effect the author wants to achieve and deepen your understanding of the analogy's purpose.
• Explore deeper meanings: Look beyond the surface-level comparison and consider the deeper meanings and implications of the analogy. Think about the layers of symbolism and metaphorical associations that the analogy may carry.

Analyzing is a key practice in any literature assignment. Read here to get an insight into literary analysis !

Let's take a closer look at a literary quote and analyze it to reveal its deeper meanings:

So, the next time you delve into a captivating literary work, keep an eye out for the analogies. Also, remember to include this device in your writings to give them a literary boost!

But if you still feel a little lost about using and analyzing analogies, you can reach out to our professional essay writing service!

At our service, our literature specialist writers can help you with any literature assignment. Whether you need help analyzing analogies or any other literary device, our team can do it all.

You can always rely on our team to provide you with assignments that will get you top scores every time.

Just ask us to “ write my essay ” and we’ll deliver!

Dr. Barbara is a highly experienced writer and author who holds a Ph.D. degree in public health from an Ivy League school. She has worked in the medical field for many years, conducting extensive research on various health topics. Her writing has been featured in several top-tier publications.

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“He’s as strong as an ox” and “Navigating her emotions is like walking through a maze” are examples of analogies, a common method of comparison in the English language. Analogies are not only prevalent in literature and writing but also in everyday speech, serving as an effective tool for communication. They involve comparing two different things or ideas, which helps clarify or emphasize a point. This literary term, known as an analogy, encompasses various types of comparisons, making it a key element in both formal and informal expression.

Like any other literary analysis sample device, Analogy is used in enhancing the meaning of a composition and is also used in helping the readers in creating a visual image in their minds as well as relationships goals and connections when they would read something difficult or sensitive by comparing one thing to the other. Analogies are often used in thesis , essay writing , report writing , and even in speeches .

What is an Analogy? – Definition An analogy is a comparison between two different things, intended to highlight some form of similarity. It’s a linguistic technique used to explain a new or complex idea by relating it to something familiar. Analogies are often used in teaching, writing, and speaking to make concepts easier to understand. They draw parallels that help people visualize and grasp the essence of the subjects being compared, thereby enhancing comprehension and retention.

Examples of Word Analogies

Analogies are crucial in language and thinking, comparing different concepts to enhance understanding. They are used in education to simplify complex ideas, in standardized tests to assess reasoning skills, and in job interviews to evaluate problem-solving abilities. Additionally, analogies enrich literature and daily communication. Examples like comparing pens to brushes or the sun to planets demonstrate how analogies illuminate various subjects, making them more accessible and relatable.

• Relationship in First Pair : A pen is a tool used for writing.
• Application to Second Pair : Similarly, a brush is a tool, but it is used for painting.
• The analogy connects the function of each tool with its primary action.
• Relationship in First Pair : The sun is a central part of our solar system.
• Application to Second Pair : In a broader scope, a planet is part of a galaxy, which is a larger system of celestial bodies.
• This analogy scales from a smaller celestial relationship (sun and solar system) to a larger one (planet and galaxy).
• Relationship in First Pair : A teacher is the guiding authority in a classroom.
• Application to Second Pair : Similarly, a captain is the guiding authority on a ship.
• The analogy compares the roles of authority and guidance in different settings.
• Relationship in First Pair : A clock is an instrument used to measure and indicate time.
• Application to Second Pair : In a similar vein, a thermometer is an instrument used to measure and indicate temperature.
• This analogy connects the function of measuring and indicating specific elements (time and temperature) with their respective instruments.
• Relationship in First Pair : A book is an individual item that is part of a collection in a library.
• Application to Second Pair : Similarly, a piece of art is an individual item that forms part of a collection in a gallery.
• The analogy shows the relationship of individual items (books, art) as components of larger collections (library, gallery).
• Leaf : Tree :: Wave : Ocean It compares the part-to-whole relationship of a leaf to a tree and a wave to an ocean.
• Author : Novel :: Composer : Symphony This analogy highlights the relationship between an author and their creation, a novel, to a composer and their creation, a symphony.
• Doctor : Hospital :: Teacher : School It parallels the role of a doctor in a hospital to that of a teacher in a school.
• Key : Piano :: String : Guitar This analogy compares the function of a key on a piano to a string on a guitar.
• Nurse : Healthcare :: Lawyer : Law Here, the analogy shows the relationship of a nurse to the field of healthcare and a lawyer to the field of law.

More Analogy Examples for You to Solve

• Owl : Night :: Eagle : _______ (Hint: Consider the time of day each bird is most active.)
• Library : Books :: Museum : _______ (Hint: Think about what a museum houses.)
• Novelist : Words :: Painter : _______ (Hint: Focus on the primary medium used by each artist.)
• Teacher : Educate :: Chef : _______ (Hint: What is the primary action a chef performs?)
• Fish : School :: Wolf : _______ (Hint: Consider the term for a group of these animals.)
• Piano : Music :: Telescope : _______ (Hint: What does a telescope help us explore?)
• Rain : Cloud :: Lava : _______ (Hint: Where does lava originate?)
• Heart : Circulate :: Lungs : _______ (Hint: Think about the primary function of lungs.)
• Leaf : Photosynthesis :: Root : _______ (Hint: Consider the main function of roots in a plant.)
• Baker : Bakery :: Librarian : _______ (Hint: Where does a librarian work?)
• Clock : Time :: Scale : _______
• Ocean : Saltwater :: Lake : _______
• Flower : Garden :: Book : _______
• Knife : Cut :: Screwdriver : _______
• Fire : Heat :: Snow : _______
• Poet : Poem :: Musician : _______
• Bird : Nest :: Bee : _______
• Tree : Oxygen :: Sun : _______
• Actor : Stage :: Athlete : _______
• Shoe : Foot :: Glove : _______
• Phone : Call :: Computer : _______
• Rain : Umbrella :: Sun : _______
• Leaf : Green :: Sky : _______
• Baker : Bread :: Winemaker : _______
• Painter : Portrait :: Writer : _______
• Doctor : Patient :: Teacher : _______
• Fisherman : Fish :: Miner : _______
• Keyboard : Type :: Mouse : _______
• Car : Garage :: Airplane : _______
• Map : Location :: Calendar : _______

Examples of Analogies for Critical Thinking

• Just as a garden is a space where flowers grow and flourish, the mind is a space where ideas are cultivated and developed. This analogy emphasizes the nurturing and growth aspects in both scenarios.
• A book opens the door to knowledge, much like a key unlocks a door. This analogy highlights the unlocking and revealing nature of a book, providing access to new information and understanding.
• A telescope enables us to see distant stars, while a microscope allows us to view tiny bacteria. This analogy draws a parallel between the tools we use to explore vastly different scales of our universe, from the vast to the microscopic.
• Just as a foundation provides stability and support for a building, roots offer support and nourishment to a tree. This analogy compares the underlying support structures in architecture and nature.
• In poetry, words are woven together to create emotional and intellectual art, just as colors are blended in a painting to create a visual masterpiece. This analogy compares the elements of creation in different forms of art.
• A chef uses a recipe to create a dish, just like a composer uses a musical score to create a symphony.
• An author crafts stories with a pen as a sculptor shapes sculptures with a chisel.
• Fire is a source of warmth, as ice is a source of coolness.
• A clock measures time like a thermometer measures temperature.
• Trees produce oxygen, and clouds produce rain.

More Examples for you to Solve:

• Helmet : Head :: Gloves : _______ (Hint: Consider what gloves protect.)
• Sponge : Absorb :: Sieve : _______ (Hint: Think about what a sieve does with liquids.)
• Caterpillar : Butterfly :: Tadpole : _______ (Hint: Consider the lifecycle transformation.)
• Magnet : Attract :: Repellent : _______ (Hint: Think of the opposite action of attracting.)
• Flashlight : Darkness :: Air Conditioner : _______ (Hint: What does an air conditioner alleviate?)
• Furnace : Heat :: Refrigerator : _______ (Hint: Think about what a refrigerator preserves.)
• Anchor : Ship :: Brakes : _______ (Hint: Consider what brakes do to a vehicle.)
• Recipe : Dish :: Blueprint : _______ (Hint: What is created using a blueprint?)
• Vaccine : Disease :: Fertilizer : _______ (Hint: Think about what fertilizer promotes.)
• Lighthouse : Ships :: Traffic Light : _______ (Hint: Consider what traffic lights guide.)
• Archive : Documents :: Museum : _______
• Rudder : Direction :: Engine : _______
• Thermometer : Temperature :: Barometer : _______
• Author : Story :: Composer : _______
• Nest : Bird :: Den : _______
• Broom : Sweep :: Hose : _______
• Window : Light :: Dam : _______
• Dew : Morning :: Frost : _______
• Key : Lock :: Code : _______
• Easel : Painter :: Anvil : _______

Analogy Examples in Sentence

• Life is like a box of chocolates; you never know what you’re going to get. This analogy compares the unpredictability of life with the surprise of picking a chocolate from an assorted box.
• The heart of a car is its engine. This draws a parallel between the essential role of the heart in the human body and the engine in a vehicle.
• A good book is a magic gateway into another world. Here, the transformative power of reading is likened to a portal leading to new, undiscovered realms.
• The classroom was a zoo. This analogy suggests the noisy and chaotic nature of the classroom, similar to the lively environment of a zoo.
• Her eyes were windows to her soul. This sentence compares eyes to windows, implying that they reveal deep emotions or the essence of a person.
• Time is a thief. This analogy implies that time steals moments from our lives, much like a thief takes away possessions.
• The computer in the modern age is like a pen in the past. This draws a comparison between the role of computers today in communication and creation, and the role of the pen in earlier times.
• The moon is a ghostly galleon tossed upon cloudy seas. This vividly portrays the moon as a ghostly ship sailing across the sky, with clouds as its sea.
• The world is a stage, and we are merely players. This famous analogy from Shakespeare suggests that life is like a play, and everyone has a role to perform.
• Watching the show was like walking through a dream. This suggests the surreal, dream-like quality of the show, likened to the experience of walking through a dream.

Examples of Analogy in Literature

Analogy is a common literary device used by authors to draw comparisons between two different things, often to highlight a particular theme or idea. Here are some examples of analogy in literature:

• This famous analogy compares the world to a stage and life to a play, suggesting that our lives are structured like a theatrical performance, with different roles and acts.
• Orwell uses farm animals to represent historical figures and social classes, drawing parallels between the farm’s descent into tyranny and the history of Soviet communism.
• Here, the prejudice and racism in Maycomb are compared to a disease, suggesting they are both harmful and spread uncontrollably.
• The diverging paths symbolize life’s different options and directions, and the choice of path represents a decision that shapes one’s future.
• In this analogy, experiences are likened to physical parts of a person, suggesting that they become integral to one’s identity.

Types of Analogy

• Literal Analogy : Compares two similar things or classes of things that have the same relationship. For example, “Just as a sword is the weapon of a warrior, a pen is the weapon of a writer.”
• Figurative Analogy : Involves a comparison between two things that are different in nature, often used to explain a concept or to persuade. For instance, comparing the mind to a computer.
• Relational Analogy : Focuses on the relationship between pairs of words. For example, “Hand is to glove as foot is to sock.” The relationship is about things that cover.
• Personal Analogy : Requires imagining oneself as an object or a situation. It’s often used in problem-solving to look at things from a different perspective.
• Predictive Analogy : Used to predict the outcome of some actions by comparing it to known outcomes in similar scenarios. For example, “If you overwater a plant, it dies; similarly, too much of anything, even a good thing, can be harmful.”
• Analogical Argument : Used in persuasive writing and speech, where an analogy is used as an argument or as a part of an argument.
• Negative Analogy : Focuses on comparing dissimilarities between two things. For example, “Arguing on the internet is unlike a sports competition; there are no clear winners.”
• Medical Analogy : Common in medical fields, where symptoms or conditions of a patient are compared to typical cases to diagnose or treat.
• Historical Analogy : Draws a comparison between historical events to explain or predict current events. For example, comparing modern political situations to historical ones.
• Mathematical Analogy : Involves comparing mathematical relationships, often used in teaching complex mathematical concepts.

How to Write an Analogy

• Identify the Core Idea or Concept : Begin by determining the main idea or concept you want to explain or enhance through the analogy.
• Find a Relatable Comparison : Choose a familiar or easily understandable object, situation, or concept that shares similarities or relationships with your core idea.
• Establish a Clear Relationship : Ensure that the relationship between the two entities in your analogy is clear and logical. The comparison should highlight the similarities or explain the concept effectively.
• Use Simple and Effective Language : The effectiveness of an analogy often lies in its simplicity. Use language that is easy to understand and avoids complexity.
• Be Consistent : Maintain consistency in the elements of your analogy. Mixing different metaphors or comparisons can lead to confusion.
• Test Your Analogy : Before finalizing, test your analogy to see if it makes the concept clearer and is understandable to your intended audience.

When to Use Analogy

• To Simplify Complex Ideas : Analogies are excellent for breaking down complex or abstract concepts into simpler, more relatable terms.
• In Teaching and Education : They are used to explain new or difficult subjects by relating them to something familiar to the students.
• To Persuade or Argue : In rhetoric and writing, analogies can make arguments more persuasive by drawing parallels that the audience can easily understand.
• To Enhance Writing : Writers often use analogies to add depth, creativity, and imagery to their writing, making it more engaging and vivid.
• In Problem-Solving : Analogies can help in seeing problems from a new perspective, leading to innovative solutions.

How Does Analogy Work

• By Establishing Relationships : Analogies work by drawing a parallel between two disparate entities, emphasizing their similarities in relation to each other.
• Through Familiarity and Understanding : They often use familiar concepts to explain unfamiliar ones, making new or complex information more digestible and easier to grasp.
• Creating Mental Images : Good analogies create vivid mental images, which can be more effective in communication than abstract concepts.
• Enhancing Memory and Retention : Because they often involve storytelling or imagery, analogies can be more memorable than straightforward explanations, aiding in better retention of the information.
• Building on Prior Knowledge : Analogies leverage the audience’s existing knowledge or experience, providing a foundation for understanding new information.

Analogies, when used effectively, can be powerful tools for communication, learning, and creativity, bridging gaps in understanding by connecting the unknown to the

25 Examples of Analogies

1. life is like a race.

2. Finding a Good Man is Like Finding a Needle in a Haystack

3. Just as a Sword is the Weapon of a Warrior, a Pen is the Weapon of a Writer

4. That’s as Useful as Rearranging Deck Chairs on the Titanic.

5. How a Doctor Diagnoses Diseases are Like How a Detective Investigates Crimes

6. Explaining a Joke is Like Dissecting a Frog

7. Just as a Caterpillar Comes out of its Cocoon, So we Must Come out of our Comfort Zone

8. A Movie is a Roller Coaster Ride of Emotions.

9. You are as Annoying as Nails on a Chalkboard.

10. Life is Like a Box of Chocolates – You Never Know What You’re Gonna Get!

11. Reasoning Analogy

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12. Analogy as the Core of Cognition

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13. Analogy by Similarity Example

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14. Semantic Analogy Example

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15. Teaching by Analogy Example

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16. Animal Analogies Example

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17. The Principle of Analogy

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18. Analogy as Exploration

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19. Science Analogy Example

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20. Practice Analogy Questions

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21. The Reaction Against Analogy

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22. Transformational Analogy Example

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23. Curve Analogies Template

24. Analogy and Transfer

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25. Analogy in Thinking Example

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What is an Analogy?

A  figurative analogy is used when you compare two completely different ideas or things and use its similarities to give an explanation of things that are hard to understand or are too sensitive. Analogies are often used in thesis , essay writing , report writing , and even in speeches .

Step 1: Identify the Two or More Things You Want to Compare

To start is to identify two or more words or phrases you may want to compare. This is the first step to writing your analogy. You must also be careful with the analogy you are going to be using, if your audiences are children, you can use analogy for kids . The important thing is to be able to explain the idea or the concept.

Step 2: Do Your Research on the Similarities

In order for you to explain and understand the similarities between the words or phrases that you are using for analogy, you must first do your research about it. Simply writing two words together to compare is not enough. It is also important for you to understand what these two words mean and how similar are they in order for them to be compared.

Step 3: Make the Analogies

Make or create the analogies once you have figured out the similarities of the words you have written. If you have not, go back to the second step and continue until you found them. The analogy must be in a simple sentence or a simple statement. Avoid using technical jargon that defeats the purpose of the analogy.

Step 4: Give the Explanation of the Chosen Analogies

The last step is to give out the explanation of the chosen analogies. The explanation will help give the reader the idea of what they are reading and can grasp the information from the analogies. Provided the fact that these chosen analogies details and examples to back it.

What is the difference with analogy, simile and metaphor?

More often than not, an analogy is sometimes mistaken with the other figures of  speech examples , namely  simile  and  metaphor , because these are used to seek relationships between concepts and things. The  figurative language  simile compares two objects that use comparison words such as ‘like’ and ‘as’ where the whole metaphor would compare two objects with the use of the said comparison words.

What are the elements of an analogy?

What you can expect in the elements of an analogy are as follows: the two or more concepts that need to be compared, the shared characteristics of these concepts, the differences of the concepts, the purpose, the clarification, and lastly the creativity.

What is the difference between analogy and idioms?

An analogy is a comparison of two or more things, topics or concepts that helps explain the topic. An idiom is a phrase that has a figurative language or meaning to it.

Analogy compares two completely different things and look for similarities between two things or concepts and it only focuses on that angle. The use and purpose of analogies may baffle any reader at first but once they would realize how analogies can help writers in making difficult and sensitive topics or things understandable, analogies might be used frequently.

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Analogy and Analogical Reasoning

An analogy is a comparison between two objects, or systems of objects, that highlights respects in which they are thought to be similar. Analogical reasoning is any type of thinking that relies upon an analogy. An analogical argument is an explicit representation of a form of analogical reasoning that cites accepted similarities between two systems to support the conclusion that some further similarity exists. In general (but not always), such arguments belong in the category of ampliative reasoning, since their conclusions do not follow with certainty but are only supported with varying degrees of strength. However, the proper characterization of analogical arguments is subject to debate (see §2.2 ).

Analogical reasoning is fundamental to human thought and, arguably, to some nonhuman animals as well. Historically, analogical reasoning has played an important, but sometimes mysterious, role in a wide range of problem-solving contexts. The explicit use of analogical arguments, since antiquity, has been a distinctive feature of scientific, philosophical and legal reasoning. This article focuses primarily on the nature, evaluation and justification of analogical arguments. Related topics include metaphor , models in science , and precedent and analogy in legal reasoning .

1. Introduction: the many roles of analogy

2.1 examples, 2.2 characterization, 2.3 plausibility, 2.4 analogical inference rules, 3.1 commonsense guidelines, 3.2 aristotle’s theory, 3.3 material criteria: hesse’s theory, 3.4 formal criteria: the structure-mapping theory, 3.5 other theories, 3.6 practice-based approaches, 4.1 deductive justification, 4.2 inductive justification, 4.3 a priori justification, 4.4 pragmatic justification, 5.1 analogy and confirmation, 5.2 conceptual change and theory development, online manuscript, related entries.

Analogies are widely recognized as playing an important heuristic role, as aids to discovery. They have been employed, in a wide variety of settings and with considerable success, to generate insight and to formulate possible solutions to problems. According to Joseph Priestley, a pioneer in chemistry and electricity,

analogy is our best guide in all philosophical investigations; and all discoveries, which were not made by mere accident, have been made by the help of it. (1769/1966: 14)

Priestley may be over-stating the case, but there is no doubt that analogies have suggested fruitful lines of inquiry in many fields. Because of their heuristic value, analogies and analogical reasoning have been a particular focus of AI research. Hájek (2018) examines analogy as a heuristic tool in philosophy.

Example 1 . Hydrodynamic analogies exploit mathematical similarities between the equations governing ideal fluid flow and torsional problems. To predict stresses in a planned structure, one can construct a fluid model, i.e., a system of pipes through which water passes (Timoshenko and Goodier 1970). Within the limits of idealization, such analogies allow us to make demonstrative inferences, for example, from a measured quantity in the fluid model to the analogous value in the torsional problem. In practice, there are numerous complications (Sterrett 2006).

At the other extreme, an analogical argument may provide very weak support for its conclusion, establishing no more than minimal plausibility. Consider:

Example 2 . Thomas Reid’s (1785) argument for the existence of life on other planets (Stebbing 1933; Mill 1843/1930; Robinson 1930; Copi 1961). Reid notes a number of similarities between Earth and the other planets in our solar system: all orbit and are illuminated by the sun; several have moons; all revolve on an axis. In consequence, he concludes, it is “not unreasonable to think, that those planets may, like our earth, be the habitation of various orders of living creatures” (1785: 24).

Such modesty is not uncommon. Often the point of an analogical argument is just to persuade people to take an idea seriously. For instance:

Example 3 . Darwin takes himself to be using an analogy between artificial and natural selection to argue for the plausibility of the latter:

Why may I not invent the hypothesis of Natural Selection (which from the analogy of domestic productions, and from what we know of the struggle of existence and of the variability of organic beings, is, in some very slight degree, in itself probable) and try whether this hypothesis of Natural Selection does not explain (as I think it does) a large number of facts…. ( Letter to Henslow , May 1860 in Darwin 1903)

Here it appears, by Darwin’s own admission, that his analogy is employed to show that the hypothesis is probable to some “slight degree” and thus merits further investigation. Some, however, reject this characterization of Darwin’s reasoning (Richards 1997; Gildenhuys 2004).

Sometimes analogical reasoning is the only available form of justification for a hypothesis. The method of ethnographic analogy is used to interpret

the nonobservable behaviour of the ancient inhabitants of an archaeological site (or ancient culture) based on the similarity of their artifacts to those used by living peoples. (Hunter and Whitten 1976: 147)

For example:

Example 4 . Shelley (1999, 2003) describes how ethnographic analogy was used to determine the probable significance of odd markings on the necks of Moche clay pots found in the Peruvian Andes. Contemporary potters in Peru use these marks (called sígnales ) to indicate ownership; the marks enable them to reclaim their work when several potters share a kiln or storage facility. Analogical reasoning may be the only avenue of inference to the past in such cases, though this point is subject to dispute (Gould and Watson 1982; Wylie 1982, 1985). Analogical reasoning may have similar significance for cosmological phenomena that are inaccessible due to limits on observation (Dardashti et al. 2017). See §5.1 for further discussion.

As philosophers and historians such as Kuhn (1996) have repeatedly pointed out, there is not always a clear separation between the two roles that we have identified, discovery and justification. Indeed, the two functions are blended in what we might call the programmatic (or paradigmatic ) role of analogy: over a period of time, an analogy can shape the development of a program of research. For example:

Example 5 . An ‘acoustical analogy’ was employed for many years by certain nineteenth-century physicists investigating spectral lines. Discrete spectra were thought to be

completely analogous to the acoustical situation, with atoms (and/or molecules) serving as oscillators originating or absorbing the vibrations in the manner of resonant tuning forks. (Maier 1981: 51)

Guided by this analogy, physicists looked for groups of spectral lines that exhibited frequency patterns characteristic of a harmonic oscillator. This analogy served not only to underwrite the plausibility of conjectures, but also to guide and limit discovery by pointing scientists in certain directions.

More generally, analogies can play an important programmatic role by guiding conceptual development (see §5.2 ). In some cases, a programmatic analogy culminates in the theoretical unification of two different areas of inquiry.

Example 6 . Descartes’s (1637/1954) correlation between geometry and algebra provided methods for systematically handling geometrical problems that had long been recognized as analogous. A very different relationship between analogy and discovery exists when a programmatic analogy breaks down, as was the ultimate fate of the acoustical analogy. That atomic spectra have an entirely different explanation became clear with the advent of quantum theory. In this case, novel discoveries emerged against background expectations shaped by the guiding analogy. There is a third possibility: an unproductive or misleading programmatic analogy may simply become entrenched and self-perpetuating as it leads us to “construct… data that conform to it” (Stepan 1996: 133). Arguably, the danger of this third possibility provides strong motivation for developing a critical account of analogical reasoning and analogical arguments.

Analogical cognition , which embraces all cognitive processes involved in discovering, constructing and using analogies, is broader than analogical reasoning (Hofstadter 2001; Hofstadter and Sander 2013). Understanding these processes is an important objective of current cognitive science research, and an objective that generates many questions. How do humans identify analogies? Do nonhuman animals use analogies in ways similar to humans? How do analogies and metaphors influence concept formation?

This entry, however, concentrates specifically on analogical arguments. Specifically, it focuses on three central epistemological questions:

• What criteria should we use to evaluate analogical arguments?
• What philosophical justification can be provided for analogical inferences?
• How do analogical arguments fit into a broader inferential context (i.e., how do we combine them with other forms of inference), especially theoretical confirmation?

Following a preliminary discussion of the basic structure of analogical arguments, the entry reviews selected attempts to provide answers to these three questions. To find such answers would constitute an important first step towards understanding the nature of analogical reasoning. To isolate these questions, however, is to make the non-trivial assumption that there can be a theory of analogical arguments —an assumption which, as we shall see, is attacked in different ways by both philosophers and cognitive scientists.

2. Analogical arguments

Analogical arguments vary greatly in subject matter, strength and logical structure. In order to appreciate this variety, it is helpful to increase our stock of examples. First, a geometric example:

Example 7 (Rectangles and boxes). Suppose that you have established that of all rectangles with a fixed perimeter, the square has maximum area. By analogy, you conjecture that of all boxes with a fixed surface area, the cube has maximum volume.

Two examples from the history of science:

Example 8 (Morphine and meperidine). In 1934, the pharmacologist Schaumann was testing synthetic compounds for their anti-spasmodic effect. These drugs had a chemical structure similar to morphine. He observed that one of the compounds— meperidine , also known as Demerol —had a physical effect on mice that was previously observed only with morphine: it induced an S-shaped tail curvature. By analogy, he conjectured that the drug might also share morphine’s narcotic effects. Testing on rats, rabbits, dogs and eventually humans showed that meperidine, like morphine, was an effective pain-killer (Lembeck 1989: 11; Reynolds and Randall 1975: 273).

Example 9 (Priestley on electrostatic force). In 1769, Priestley suggested that the absence of electrical influence inside a hollow charged spherical shell was evidence that charges attract and repel with an inverse square force. He supported his hypothesis by appealing to the analogous situation of zero gravitational force inside a hollow shell of uniform density.

Finally, an example from legal reasoning:

Example 10 (Duty of reasonable care). In a much-cited case ( Donoghue v. Stevenson 1932 AC 562), the United Kingdom House of Lords found the manufacturer of a bottle of ginger beer liable for damages to a consumer who became ill as a result of a dead snail in the bottle. The court argued that the manufacturer had a duty to take “reasonable care” in creating a product that could foreseeably result in harm to the consumer in the absence of such care, and where the consumer had no possibility of intermediate examination. The principle articulated in this famous case was extended, by analogy, to allow recovery for harm against an engineering firm whose negligent repair work caused the collapse of a lift ( Haseldine v. CA Daw & Son Ltd. 1941 2 KB 343). By contrast, the principle was not applicable to a case where a workman was injured by a defective crane, since the workman had opportunity to examine the crane and was even aware of the defects ( Farr v. Butters Brothers & Co. 1932 2 KB 606).

What, if anything, do all of these examples have in common? We begin with a simple, quasi-formal characterization. Similar formulations are found in elementary critical thinking texts (e.g., Copi and Cohen 2005) and in the literature on argumentation theory (e.g., Govier 1999, Guarini 2004, Walton and Hyra 2018). An analogical argument has the following form:

• \(S\) is similar to \(T\) in certain (known) respects.
• \(S\) has some further feature \(Q\).
• Therefore, \(T\) also has the feature \(Q\), or some feature \(Q^*\) similar to \(Q\).

(1) and (2) are premises. (3) is the conclusion of the argument. The argument form is ampliative ; the conclusion is not guaranteed to follow from the premises.

\(S\) and \(T\) are referred to as the source domain and target domain , respectively. A domain is a set of objects, properties, relations and functions, together with a set of accepted statements about those objects, properties, relations and functions. More formally, a domain consists of a set of objects and an interpreted set of statements about them. The statements need not belong to a first-order language, but to keep things simple, any formalizations employed here will be first-order. We use unstarred symbols \((a, P, R, f)\) to refer to items in the source domain and starred symbols \((a^*, P^*, R^*, f^*)\) to refer to corresponding items in the target domain. In Example 9 , the source domain items pertain to gravitation; the target items pertain to electrostatic attraction.

Formally, an analogy between \(S\) and \(T\) is a one-to-one mapping between objects, properties, relations and functions in \(S\) and those in \(T\). Not all of the items in \(S\) and \(T\) need to be placed in correspondence. Commonly, the analogy only identifies correspondences between a select set of items. In practice, we specify an analogy simply by indicating the most significant similarities (and sometimes differences).

We can improve on this preliminary characterization of the argument from analogy by introducing the tabular representation found in Hesse (1966). We place corresponding objects, properties, relations and propositions side-by-side in a table of two columns, one for each domain. For instance, Reid’s argument ( Example 2 ) can be represented as follows (using \(\Rightarrow\) for the analogical inference):

Hesse introduced useful terminology based on this tabular representation. The horizontal relations in an analogy are the relations of similarity (and difference) in the mapping between domains, while the vertical relations are those between the objects, relations and properties within each domain. The correspondence (similarity) between earth’s having a moon and Mars’ having moons is a horizontal relation; the causal relation between having a moon and supporting life is a vertical relation within the source domain (with the possibility of a distinct such relation existing in the target as well).

In an earlier discussion of analogy, Keynes (1921) introduced some terminology that is also helpful.

Positive analogy . Let \(P\) stand for a list of accepted propositions \(P_1 , \ldots ,P_n\) about the source domain \(S\). Suppose that the corresponding propositions \(P^*_1 , \ldots ,P^*_n\), abbreviated as \(P^*\), are all accepted as holding for the target domain \(T\), so that \(P\) and \(P^*\) represent accepted (or known) similarities. Then we refer to \(P\) as the positive analogy .

Negative analogy . Let \(A\) stand for a list of propositions \(A_1 , \ldots ,A_r\) accepted as holding in \(S\), and \(B^*\) for a list \(B_1^*, \ldots ,B_s^*\) of propositions holding in \(T\). Suppose that the analogous propositions \(A^* = A_1^*, \ldots ,A_r^*\) fail to hold in \(T\), and similarly the propositions \(B = B_1 , \ldots ,B_s\) fail to hold in \(S\), so that \(A, {\sim}A^*\) and \({\sim}B, B^*\) represent accepted (or known) differences. Then we refer to \(A\) and \(B\) as the negative analogy .

Neutral analogy . The neutral analogy consists of accepted propositions about \(S\) for which it is not known whether an analogue holds in \(T\).

Finally we have:

Hypothetical analogy . The hypothetical analogy is simply the proposition \(Q\) in the neutral analogy that is the focus of our attention.

These concepts allow us to provide a characterization for an individual analogical argument that is somewhat richer than the original one.

An analogical argument may thus be summarized:

It is plausible that \(Q^*\) holds in the target, because of certain known (or accepted) similarities with the source domain, despite certain known (or accepted) differences.

In order for this characterization to be meaningful, we need to say something about the meaning of ‘plausibly.’ To ensure broad applicability over analogical arguments that vary greatly in strength, we interpret plausibility rather liberally as meaning ‘with some degree of support’. In general, judgments of plausibility are made after a claim has been formulated, but prior to rigorous testing or proof. The next sub-section provides further discussion.

Note that this characterization is incomplete in a number of ways. The manner in which we list similarities and differences, the nature of the correspondences between domains: these things are left unspecified. Nor does this characterization accommodate reasoning with multiple analogies (i.e., multiple source domains), which is ubiquitous in legal reasoning and common elsewhere. To characterize the argument form more fully, however, is not possible without either taking a step towards a substantive theory of analogical reasoning or restricting attention to certain classes of analogical arguments.

Arguments by analogy are extensively discussed within argumentation theory. There is considerable debate about whether they constitute a species of deductive inference (Govier 1999; Waller 2001; Guarini 2004; Kraus 2015). Argumentation theorists also make use of tools such as speech act theory (Bermejo-Luque 2012), argumentation schemes and dialogue types (Macagno et al. 2017; Walton and Hyra 2018) to distinguish different types of analogical argument.

Arguments by analogy are also discussed in the vast literature on scientific models and model-based reasoning, following the lead of Hesse (1966). Bailer-Jones (2002) draws a helpful distinction between analogies and models. While “many models have their roots in an analogy” (2002: 113) and analogy “can act as a catalyst to aid modeling,” Bailer-Jones observes that “the aim of modeling has nothing intrinsically to do with analogy.” In brief, models are tools for prediction and explanation, whereas analogical arguments aim at establishing plausibility. An analogy is evaluated in terms of source-target similarity, while a model is evaluated on how successfully it “provides access to a phenomenon in that it interprets the available empirical data about the phenomenon.” If we broaden our perspective beyond analogical arguments , however, the connection between models and analogies is restored. Nersessian (2009), for instance, stresses the role of analog models in concept-formation and other cognitive processes.

To say that a hypothesis is plausible is to convey that it has epistemic support: we have some reason to believe it, even prior to testing. An assertion of plausibility within the context of an inquiry typically has pragmatic connotations as well: to say that a hypothesis is plausible suggests that we have some reason to investigate it further. For example, a mathematician working on a proof regards a conjecture as plausible if it “has some chances of success” (Polya 1954 (v. 2): 148). On both points, there is ambiguity as to whether an assertion of plausibility is categorical or a matter of degree. These observations point to the existence of two distinct conceptions of plausibility, probabilistic and modal , either of which may reflect the intended conclusion of an analogical argument.

On the probabilistic conception, plausibility is naturally identified with rational credence (rational subjective degree of belief) and is typically represented as a probability. A classic expression may be found in Mill’s analysis of the argument from analogy in A System of Logic :

There can be no doubt that every resemblance [not known to be irrelevant] affords some degree of probability, beyond what would otherwise exist, in favour of the conclusion. (Mill 1843/1930: 333)

In the terminology introduced in §2.2, Mill’s idea is that each element of the positive analogy boosts the probability of the conclusion. Contemporary ‘structure-mapping’ theories ( §3.4 ) employ a restricted version: each structural similarity between two domains contributes to the overall measure of similarity, and hence to the strength of the analogical argument.

On the alternative modal conception, ‘it is plausible that \(p\)’ is not a matter of degree. The meaning, roughly speaking, is that there are sufficient initial grounds for taking \(p\) seriously, i.e., for further investigation (subject to feasibility and interest). Informally: \(p\) passes an initial screening procedure. There is no assertion of degree. Instead, ‘It is plausible that’ may be regarded as an epistemic modal operator that aims to capture a notion, prima facie plausibility, that is somewhat stronger than ordinary epistemic possibility. The intent is to single out \(p\) from an undifferentiated mass of ideas that remain bare epistemic possibilities. To illustrate: in 1769, Priestley’s argument ( Example 9 ), if successful, would establish the prima facie plausibility of an inverse square law for electrostatic attraction. The set of epistemic possibilities—hypotheses about electrostatic attraction compatible with knowledge of the day—was much larger. Individual analogical arguments in mathematics (such as Example 7 ) are almost invariably directed towards prima facie plausibility.

The modal conception figures importantly in some discussions of analogical reasoning. The physicist N. R. Campbell (1957) writes:

But in order that a theory may be valuable it must … display an analogy. The propositions of the hypothesis must be analogous to some known laws…. (1957: 129)

Commenting on the role of analogy in Fourier’s theory of heat conduction, Campbell writes:

Some analogy is essential to it; for it is only this analogy which distinguishes the theory from the multitude of others… which might also be proposed to explain the same laws. (1957: 142)

The interesting notion here is that of a “valuable” theory. We may not agree with Campbell that the existence of analogy is “essential” for a novel theory to be “valuable.” But consider the weaker thesis that an acceptable analogy is sufficient to establish that a theory is “valuable”, or (to qualify still further) that an acceptable analogy provides defeasible grounds for taking the theory seriously. (Possible defeaters might include internal inconsistency, inconsistency with accepted theory, or the existence of a (clearly superior) rival analogical argument.) The point is that Campbell, following the lead of 19 th century philosopher-scientists such as Herschel and Whewell, thinks that analogies can establish this sort of prima facie plausibility. Snyder (2006) provides a detailed discussion of the latter two thinkers and their ideas about the role of analogies in science.

In general, analogical arguments may be directed at establishing either sort of plausibility for their conclusions; they can have a probabilistic use or a modal use. Examples 7 through 9 are best interpreted as supporting modal conclusions. In those arguments, an analogy is used to show that a conjecture is worth taking seriously. To insist on putting the conclusion in probabilistic terms distracts attention from the point of the argument. The conclusion might be modeled (by a Bayesian) as having a certain probability value because it is deemed prima facie plausible, but not vice versa. Example 2 , perhaps, might be regarded as directed primarily towards a probabilistic conclusion.

There should be connections between the two conceptions. Indeed, we might think that the same analogical argument can establish both prima facie plausibility and a degree of probability for a hypothesis. But it is difficult to translate between epistemic modal concepts and probabilities (Cohen 1980; Douven and Williamson 2006; Huber 2009; Spohn 2009, 2012). We cannot simply take the probabilistic notion as the primitive one. It seems wise to keep the two conceptions of plausibility separate.

Schema (4) is a template that represents all analogical arguments, good and bad. It is not an inference rule. Despite the confidence with which particular analogical arguments are advanced, nobody has ever formulated an acceptable rule, or set of rules, for valid analogical inferences. There is not even a plausible candidate. This situation is in marked contrast not only with deductive reasoning, but also with elementary forms of inductive reasoning, such as induction by enumeration.

Of course, it is difficult to show that no successful analogical inference rule will ever be proposed. But consider the following candidate, formulated using the concepts of schema (4) and taking us only a short step beyond that basic characterization.

Rule (5) is modeled on the straight rule for enumerative induction and inspired by Mill’s view of analogical inference, as described in §2.3. We use the generic phrase ‘degree of support’ in place of probability, since other factors besides the analogical argument may influence our probability assignment for \(Q^*\).

It is pretty clear that (5) is a non-starter. The main problem is that the rule justifies too much. The only substantive requirement introduced by (5) is that there be a nonempty positive analogy. Plainly, there are analogical arguments that satisfy this condition but establish no prima facie plausibility and no measure of support for their conclusions.

Here is a simple illustration. Achinstein (1964: 328) observes that there is a formal analogy between swans and line segments if we take the relation ‘has the same color as’ to correspond to ‘is congruent with’. Both relations are reflexive, symmetric, and transitive. Yet it would be absurd to find positive support from this analogy for the idea that we are likely to find congruent lines clustered in groups of two or more, just because swans of the same color are commonly found in groups. The positive analogy is antecedently known to be irrelevant to the hypothetical analogy. In such a case, the analogical inference should be utterly rejected. Yet rule (5) would wrongly assign non-zero degree of support.

To generalize the difficulty: not every similarity increases the probability of the conclusion and not every difference decreases it. Some similarities and differences are known to be (or accepted as being) utterly irrelevant and should have no influence whatsoever on our probability judgments. To be viable, rule (5) would need to be supplemented with considerations of relevance , which depend upon the subject matter, historical context and logical details particular to each analogical argument. To search for a simple rule of analogical inference thus appears futile.

Carnap and his followers (Carnap 1980; Kuipers 1988; Niiniluoto 1988; Maher 2000; Romeijn 2006) have formulated principles of analogy for inductive logic, using Carnapian \(\lambda \gamma\) rules. Generally, this body of work relates to “analogy by similarity”, rather than the type of analogical reasoning discussed here. Romeijn (2006) maintains that there is a relation between Carnap’s concept of analogy and analogical prediction. His approach is a hybrid of Carnap-style inductive rules and a Bayesian model. Such an approach would need to be generalized to handle the kinds of arguments described in §2.1 . It remains unclear that the Carnapian approach can provide a general rule for analogical inference.

Norton (2010, and 2018—see Other Internet Resources) has argued that the project of formalizing inductive reasoning in terms of one or more simple formal schemata is doomed. His criticisms seem especially apt when applied to analogical reasoning. He writes:

If analogical reasoning is required to conform only to a simple formal schema, the restriction is too permissive. Inferences are authorized that clearly should not pass muster… The natural response has been to develop more elaborate formal templates… The familiar difficulty is that these embellished schema never seem to be quite embellished enough; there always seems to be some part of the analysis that must be handled intuitively without guidance from strict formal rules. (2018: 1)

Norton takes the point one step further, in keeping with his “material theory” of inductive inference. He argues that there is no universal logical principle that “powers” analogical inference “by asserting that things that share some properties must share others.” Rather, each analogical inference is warranted by some local constellation of facts about the target system that he terms “the fact of analogy”. These local facts are to be determined and investigated on a case by case basis.

To embrace a purely formal approach to analogy and to abjure formalization entirely are two extremes in a spectrum of strategies. There are intermediate positions. Most recent analyses (both philosophical and computational) have been directed towards elucidating criteria and procedures, rather than formal rules, for reasoning by analogy. So long as these are not intended to provide a universal ‘logic’ of analogy, there is room for such criteria even if one accepts Norton’s basic point. The next section discusses some of these criteria and procedures.

3. Criteria for evaluating analogical arguments

Logicians and philosophers of science have identified ‘textbook-style’ general guidelines for evaluating analogical arguments (Mill 1843/1930; Keynes 1921; Robinson 1930; Stebbing 1933; Copi and Cohen 2005; Moore and Parker 1998; Woods, Irvine, and Walton 2004). Here are some of the most important ones:

These principles can be helpful, but are frequently too vague to provide much insight. How do we count similarities and differences in applying (G1) and (G2)? Why are the structural and causal analogies mentioned in (G5) and (G6) especially important, and which structural and causal features merit attention? More generally, in connection with the all-important (G7): how do we determine which similarities and differences are relevant to the conclusion? Furthermore, what are we to say about similarities and differences that have been omitted from an analogical argument but might still be relevant?

An additional problem is that the criteria can pull in different directions. To illustrate, consider Reid’s argument for life on other planets ( Example 2 ). Stebbing (1933) finds Reid’s argument “suggestive” and “not unplausible” because the conclusion is weak (G4), while Mill (1843/1930) appears to reject the argument on account of our vast ignorance of properties that might be relevant (G3).

There is a further problem that relates to the distinction just made (in §2.3 ) between two kinds of plausibility. Each of the above criteria apart from (G7) is expressed in terms of the strength of the argument, i.e., the degree of support for the conclusion. The criteria thus appear to presuppose the probabilistic interpretation of plausibility. The problem is that a great many analogical arguments aim to establish prima facie plausibility rather than any degree of probability. Most of the guidelines are not directly applicable to such arguments.

Aristotle sets the stage for all later theories of analogical reasoning. In his theoretical reflections on analogy and in his most judicious examples, we find a sober account that lays the foundation both for the commonsense guidelines noted above and for more sophisticated analyses.

Although Aristotle employs the term analogy ( analogia ) and discusses analogical predication , he never talks about analogical reasoning or analogical arguments per se . He does, however, identify two argument forms, the argument from example ( paradeigma ) and the argument from likeness ( homoiotes ), both closely related to what would we now recognize as an analogical argument.

The argument from example ( paradeigma ) is described in the Rhetoric and the Prior Analytics :

Enthymemes based upon example are those which proceed from one or more similar cases, arrive at a general proposition, and then argue deductively to a particular inference. ( Rhetoric 1402b15) Let \(A\) be evil, \(B\) making war against neighbours, \(C\) Athenians against Thebans, \(D\) Thebans against Phocians. If then we wish to prove that to fight with the Thebans is an evil, we must assume that to fight against neighbours is an evil. Conviction of this is obtained from similar cases, e.g., that the war against the Phocians was an evil to the Thebans. Since then to fight against neighbours is an evil, and to fight against the Thebans is to fight against neighbours, it is clear that to fight against the Thebans is an evil. ( Pr. An. 69a1)

Aristotle notes two differences between this argument form and induction (69a15ff.): it “does not draw its proof from all the particular cases” (i.e., it is not a “complete” induction), and it requires an additional (deductively valid) syllogism as the final step. The argument from example thus amounts to single-case induction followed by deductive inference. It has the following structure (using \(\supset\) for the conditional):

In the terminology of §2.2, \(P\) is the positive analogy and \(Q\) is the hypothetical analogy. In Aristotle’s example, \(S\) (the source) is war between Phocians and Thebans, \(T\) (the target) is war between Athenians and Thebans, \(P\) is war between neighbours, and \(Q\) is evil. The first inference (dashed arrow) is inductive; the second and third (solid arrows) are deductively valid.

The paradeigma has an interesting feature: it is amenable to an alternative analysis as a purely deductive argument form. Let us concentrate on Aristotle’s assertion, “we must assume that to fight against neighbours is an evil,” represented as \(\forall x(P(x) \supset Q(x))\). Instead of regarding this intermediate step as something reached by induction from a single case, we might instead regard it as a hidden presupposition. This transforms the paradeigma into a syllogistic argument with a missing or enthymematic premise, and our attention shifts to possible means for establishing that premise (with single-case induction as one such means). Construed in this way, Aristotle’s paradeigma argument foreshadows deductive analyses of analogical reasoning (see §4.1 ).

The argument from likeness ( homoiotes ) seems to be closer than the paradeigma to our contemporary understanding of analogical arguments. This argument form receives considerable attention in Topics I, 17 and 18 and again in VIII, 1. The most important passage is the following.

Try to secure admissions by means of likeness; for such admissions are plausible, and the universal involved is less patent; e.g. that as knowledge and ignorance of contraries is the same, so too perception of contraries is the same; or vice versa, that since the perception is the same, so is the knowledge also. This argument resembles induction, but is not the same thing; for in induction it is the universal whose admission is secured from the particulars, whereas in arguments from likeness, what is secured is not the universal under which all the like cases fall. ( Topics 156b10–17)

This passage occurs in a work that offers advice for framing dialectical arguments when confronting a somewhat skeptical interlocutor. In such situations, it is best not to make one’s argument depend upon securing agreement about any universal proposition. The argument from likeness is thus clearly distinct from the paradeigma , where the universal proposition plays an essential role as an intermediate step in the argument. The argument from likeness, though logically less straightforward than the paradeigma , is exactly the sort of analogical reasoning we want when we are unsure about underlying generalizations.

In Topics I 17, Aristotle states that any shared attribute contributes some degree of likeness. It is natural to ask when the degree of likeness between two things is sufficiently great to warrant inferring a further likeness. In other words, when does the argument from likeness succeed? Aristotle does not answer explicitly, but a clue is provided by the way he justifies particular arguments from likeness. As Lloyd (1966) has observed, Aristotle typically justifies such arguments by articulating a (sometimes vague) causal principle which governs the two phenomena being compared. For example, Aristotle explains the saltiness of the sea, by analogy with the saltiness of sweat, as a kind of residual earthy stuff exuded in natural processes such as heating. The common principle is this:

Everything that grows and is naturally generated always leaves a residue, like that of things burnt, consisting in this sort of earth. ( Mete 358a17)

From this method of justification, we might conjecture that Aristotle believes that the important similarities are those that enter into such general causal principles.

Summarizing, Aristotle’s theory provides us with four important and influential criteria for the evaluation of analogical arguments:

• The strength of an analogy depends upon the number of similarities.
• Similarity reduces to identical properties and relations.
• Good analogies derive from underlying common causes or general laws.
• A good analogical argument need not pre-suppose acquaintance with the underlying universal (generalization).

These four principles form the core of a common-sense model for evaluating analogical arguments (which is not to say that they are correct; indeed, the first three will shortly be called into question). The first, as we have seen, appears regularly in textbook discussions of analogy. The second is largely taken for granted, with important exceptions in computational models of analogy ( §3.4 ). Versions of the third are found in most sophisticated theories. The final point, which distinguishes the argument from likeness and the argument from example, is endorsed in many discussions of analogy (e.g., Quine and Ullian 1970).

A slight generalization of Aristotle’s first principle helps to prepare the way for discussion of later developments. As that principle suggests, Aristotle, in common with just about everyone else who has written about analogical reasoning, organizes his analysis of the argument form around overall similarity. In the terminology of section 2.2, horizontal relationships drive the reasoning: the greater the overall similarity of the two domains, the stronger the analogical argument . Hume makes the same point, though stated negatively, in his Dialogues Concerning Natural Religion :

Wherever you depart, in the least, from the similarity of the cases, you diminish proportionably the evidence; and may at last bring it to a very weak analogy, which is confessedly liable to error and uncertainty. (1779/1947: 144)

Most theories of analogy agree with Aristotle and Hume on this general point. Disagreement relates to the appropriate way of measuring overall similarity. Some theories assign greatest weight to material analogy , which refers to shared, and typically observable, features. Others give prominence to formal analogy , emphasizing high-level structural correspondence. The next two sub-sections discuss representative accounts that illustrate these two approaches.

Hesse (1966) offers a sharpened version of Aristotle’s theory, specifically focused on analogical arguments in the sciences. She formulates three requirements that an analogical argument must satisfy in order to be acceptable:

• Requirement of material analogy . The horizontal relations must include similarities between observable properties.
• Causal condition . The vertical relations must be causal relations “in some acceptable scientific sense” (1966: 87).
• No-essential-difference condition . The essential properties and causal relations of the source domain must not have been shown to be part of the negative analogy.

3.3.1 Requirement of material analogy

For Hesse, an acceptable analogical argument must include “observable similarities” between domains, which she refers to as material analogy . Material analogy is contrasted with formal analogy . Two domains are formally analogous if both are “interpretations of the same formal theory” (1966: 68). Nomic isomorphism (Hempel 1965) is a special case in which the physical laws governing two systems have identical mathematical form. Heat and fluid flow exhibit nomic isomorphism. A second example is the analogy between the flow of electric current in a wire and fluid in a pipe. Ohm’s law

states that voltage difference along a wire equals current times a constant resistance. This has the same mathematical form as Poiseuille’s law (for ideal fluids):

which states that the pressure difference along a pipe equals the volumetric flow rate times a constant. Both of these systems can be represented by a common equation. While formal analogy is linked to common mathematical structure, it should not be limited to nomic isomorphism (Bartha 2010: 209). The idea of formal analogy generalizes to cases where there is a common mathematical structure between models for two systems. Bartha offers an even more liberal definition (2010: 195): “Two features are formally similar if they occupy corresponding positions in formally analogous theories. For example, pitch in the theory of sound corresponds to color in the theory of light.”

By contrast, material analogy consists of what Hesse calls “observable” or “pre-theoretic” similarities. These are horizontal relationships of similarity between properties of objects in the source and the target. Similarities between echoes (sound) and reflection (light), for instance, were recognized long before we had any detailed theories about these phenomena. Hesse (1966, 1988) regards such similarities as metaphorical relationships between the two domains and labels them “pre-theoretic” because they draw on personal and cultural experience. We have both material and formal analogies between sound and light, and it is significant for Hesse that the former are independent of the latter.

There are good reasons not to accept Hesse’s requirement of material analogy, construed in this narrow way. First, it is apparent that formal analogies are the starting point in many important inferences. That is certainly the case in mathematics, a field in which material analogy, in Hesse’s sense, plays no role at all. Analogical arguments based on formal analogy have also been extremely influential in physics (Steiner 1989, 1998).

In Norton’s broad sense, however, ‘material analogy’ simply refers to similarities rooted in factual knowledge of the source and target domains. With reference to this broader meaning, Hesse proposes two additional material criteria.

3.3.2 Causal condition

Hesse requires that the hypothetical analogy, the feature transferred to the target domain, be causally related to the positive analogy. In her words, the essential requirement for a good argument from analogy is “a tendency to co-occurrence”, i.e., a causal relationship. She states the requirement as follows:

The vertical relations in the model [source] are causal relations in some acceptable scientific sense, where there are no compelling a priori reasons for denying that causal relations of the same kind may hold between terms of the explanandum [target]. (1966: 87)

The causal condition rules out analogical arguments where there is no causal knowledge of the source domain. It derives support from the observation that many analogies do appear to involve a transfer of causal knowledge.

The causal condition is on the right track, but is arguably too restrictive. For example, it rules out analogical arguments in mathematics. Even if we limit attention to the empirical sciences, persuasive analogical arguments may be founded upon strong statistical correlation in the absence of any known causal connection. Consider ( Example 11 ) Benjamin Franklin’s prediction, in 1749, that pointed metal rods would attract lightning, by analogy with the way they attracted the “electrical fluid” in the laboratory:

Electrical fluid agrees with lightning in these particulars: 1. Giving light. 2. Colour of the light. 3. Crooked direction. 4. Swift motion. 5. Being conducted by metals. 6. Crack or noise in exploding. 7. Subsisting in water or ice. 8. Rending bodies it passes through. 9. Destroying animals. 10. Melting metals. 11. Firing inflammable substances. 12. Sulphureous smell.—The electrical fluid is attracted by points.—We do not know whether this property is in lightning.—But since they agree in all the particulars wherein we can already compare them, is it not probable they agree likewise in this? Let the experiment be made. ( Benjamin Franklin’s Experiments , 334)

Franklin’s hypothesis was based on a long list of properties common to the target (lightning) and source (electrical fluid in the laboratory). There was no known causal connection between the twelve “particulars” and the thirteenth property, but there was a strong correlation. Analogical arguments may be plausible even where there are no known causal relations.

3.3.3 No-essential-difference condition

Hesse’s final requirement is that the “essential properties and causal relations of the [source] have not been shown to be part of the negative analogy” (1966: 91). Hesse does not provide a definition of “essential,” but suggests that a property or relation is essential if it is “causally closely related to the known positive analogy.” For instance, an analogy with fluid flow was extremely influential in developing the theory of heat conduction. Once it was discovered that heat was not conserved, however, the analogy became unacceptable (according to Hesse) because conservation was so central to the theory of fluid flow.

This requirement, though once again on the right track, seems too restrictive. It can lead to the rejection of a good analogical argument. Consider the analogy between a two-dimensional rectangle and a three-dimensional box ( Example 7 ). Broadening Hesse’s notion, it seems that there are many ‘essential’ differences between rectangles and boxes. This does not mean that we should reject every analogy between rectangles and boxes out of hand. The problem derives from the fact that Hesse’s condition is applied to the analogy relation independently of the use to which that relation is put. What counts as essential should vary with the analogical argument. Absent an inferential context, it is impossible to evaluate the importance or ‘essentiality’ of similarities and differences.

Despite these weaknesses, Hesse’s ‘material’ criteria constitute a significant advance in our understanding of analogical reasoning. The causal condition and the no-essential-difference condition incorporate local factors, as urged by Norton, into the assessment of analogical arguments. These conditions, singly or taken together, imply that an analogical argument can fail to generate any support for its conclusion, even when there is a non-empty positive analogy. Hesse offers no theory about the ‘degree’ of analogical support. That makes her account one of the few that is oriented towards the modal, rather than probabilistic, use of analogical arguments ( §2.3 ).

Many people take the concept of model-theoretic isomorphism to set the standard for thinking about similarity and its role in analogical reasoning. They propose formal criteria for evaluating analogies, based on overall structural or syntactical similarity. Let us refer to theories oriented around such criteria as structuralist .

A number of leading computational models of analogy are structuralist. They are implemented in computer programs that begin with (or sometimes build) representations of the source and target domains, and then construct possible analogy mappings. Analogical inferences emerge as a consequence of identifying the ‘best mapping.’ In terms of criteria for analogical reasoning, there are two main ideas. First, the goodness of an analogical argument is based on the goodness of the associated analogy mapping . Second, the goodness of the analogy mapping is given by a metric that indicates how closely it approximates isomorphism.

The most influential structuralist theory has been Gentner’s structure-mapping theory, implemented in a program called the structure-mapping engine (SME). In its original form (Gentner 1983), the theory assesses analogies on purely structural grounds. Gentner asserts:

Analogies are about relations, rather than simple features. No matter what kind of knowledge (causal models, plans, stories, etc.), it is the structural properties (i.e., the interrelationships between the facts) that determine the content of an analogy. (Falkenhainer, Forbus, and Gentner 1989/90: 3)

In order to clarify this thesis, Gentner introduces a distinction between properties , or monadic predicates, and relations , which have multiple arguments. She further distinguishes among different orders of relations and functions, defined inductively (in terms of the order of the relata or arguments). The best mapping is determined by systematicity : the extent to which it places higher-order relations, and items that are nested in higher-order relations, in correspondence. Gentner’s Systematicity Principle states:

A predicate that belongs to a mappable system of mutually interconnecting relationships is more likely to be imported into the target than is an isolated predicate. (1983: 163)

A systematic analogy (one that places high-order relations and their components in correspondence) is better than a less systematic analogy. Hence, an analogical inference has a degree of plausibility that increases monotonically with the degree of systematicity of the associated analogy mapping. Gentner’s fundamental criterion for evaluating candidate analogies (and analogical inferences) thus depends solely upon the syntax of the given representations and not at all upon their content.

Later versions of the structure-mapping theory incorporate refinements (Forbus, Ferguson, and Gentner 1994; Forbus 2001; Forbus et al. 2007; Forbus et al. 2008; Forbus et al 2017). For example, the earliest version of the theory is vulnerable to worries about hand-coded representations of source and target domains. Gentner and her colleagues have attempted to solve this problem in later work that generates LISP representations from natural language text (see Turney 2008 for a different approach).

The most important challenges for the structure-mapping approach relate to the Systematicity Principle itself. Does the value of an analogy derive entirely, or even chiefly, from systematicity? There appear to be two main difficulties with this view. First: it is not always appropriate to give priority to systematic, high-level relational matches. Material criteria, and notably what Gentner refers to as “superficial feature matches,” can be extremely important in some types of analogical reasoning, such as ethnographic analogies which are based, to a considerable degree, on surface resemblances between artifacts. Second and more significantly: systematicity seems to be at best a fallible marker for good analogies rather than the essence of good analogical reasoning.

Greater systematicity is neither necessary nor sufficient for a more plausible analogical inference. It is obvious that increased systematicity is not sufficient for increased plausibility. An implausible analogy can be represented in a form that exhibits a high degree of structural parallelism. High-order relations can come cheap, as we saw with Achinstein’s “swan” example ( §2.4 ).

More pointedly, increased systematicity is not necessary for greater plausibility. Indeed, in causal analogies, it may even weaken the inference. That is because systematicity takes no account of the type of causal relevance, positive or negative. (McKay 1993) notes that microbes have been found in frozen lakes in Antarctica; by analogy, simple life forms might exist on Mars. Freezing temperatures are preventive or counteracting causes; they are negatively relevant to the existence of life. The climate of Mars was probably more favorable to life 3.5 billion years ago than it is today, because temperatures were warmer. Yet the analogy between Antarctica and present-day Mars is more systematic than the analogy between Antarctica and ancient Mars. According to the Systematicity Principle , the analogy with Antarctica provides stronger support for life on Mars today than it does for life on ancient Mars.

The point of this example is that increased systematicity does not always increase plausibility, and reduced systematicity does not always decrease it (see Lee and Holyoak 2008). The more general point is that systematicity can be misleading, unless we take into account the nature of the relationships between various factors and the hypothetical analogy. Systematicity does not magically produce or explain the plausibility of an analogical argument. When we reason by analogy, we must determine which features of both domains are relevant and how they relate to the analogical conclusion. There is no short-cut via syntax.

Schlimm (2008) offers an entirely different critique of the structure-mapping theory from the perspective of analogical reasoning in mathematics—a domain where one might expect a formal approach such as structure mapping to perform well. Schlimm introduces a simple distinction: a domain is object-rich if the number of objects is greater than the number of relations (and properties), and relation-rich otherwise. Proponents of the structure-mapping theory typically focus on relation-rich examples (such as the analogy between the solar system and the atom). By contrast, analogies in mathematics typically involve domains with an enormous number of objects (like the real numbers), but relatively few relations and functions (addition, multiplication, less-than).

Schlimm provides an example of an analogical reasoning problem in group theory that involves a single relation in each domain. In this case, attaining maximal systematicity is trivial. The difficulty is that, compatible with maximal systematicity, there are different ways in which the objects might be placed in correspondence. The structure-mapping theory appears to yield the wrong inference. We might put the general point as follows: in object-rich domains, systematicity ceases to be a reliable guide to plausible analogical inference.

3.5.1 Connectionist models

During the past thirty-five years, cognitive scientists have conducted extensive research on analogy. Gentner’s SME is just one of many computational theories, implemented in programs that construct and use analogies. Three helpful anthologies that span this period are Helman 1988; Gentner, Holyoak, and Kokinov 2001; and Kokinov, Holyoak, and Gentner 2009.

One predominant objective of this research has been to model the cognitive processes involved in using analogies. Early models tended to be oriented towards “understanding the basic constraints that govern human analogical thinking” (Hummel and Holyoak 1997: 458). Recent connectionist models have been directed towards uncovering the psychological mechanisms that come into play when we use analogies: retrieval of a relevant source domain, analogical mapping across domains, and transfer of information and learning of new categories or schemas.

In some cases, such as the structure-mapping theory (§3.4), this research overlaps directly with the normative questions that are the focus of this entry; indeed, Gentner’s Systematicity Principle may be interpreted normatively. In other cases, we might view the projects as displacing those traditional normative questions with up-to-date, computational forms of naturalized epistemology . Two approaches are singled out here because both raise important challenges to the very idea of finding sharp answers to those questions, and both suggest that connectionist models offer a more fruitful approach to understanding analogical reasoning.

The first is the constraint-satisfaction model (also known as the multiconstraint theory ), developed by Holyoak and Thagard (1989, 1995). Like Gentner, Holyoak and Thagard regard the heart of analogical reasoning as analogy mapping , and they stress the importance of systematicity, which they refer to as a structural constraint. Unlike Gentner, they acknowledge two additional types of constraints. Pragmatic constraints take into account the goals and purposes of the agent, recognizing that “the purpose will guide selection” of relevant similarities. Semantic constraints represent estimates of the degree to which people regard source and target items as being alike, rather like Hesse’s “pre-theoretic” similarities.

The novelty of the multiconstraint theory is that these structural , semantic and pragmatic constraints are implemented not as rigid rules, but rather as ‘pressures’ supporting or inhibiting potential pairwise correspondences. The theory is implemented in a connectionist program called ACME (Analogical Constraint Mapping Engine), which assigns an initial activation value to each possible pairing between elements in the source and target domains (based on semantic and pragmatic constraints), and then runs through cycles that update the activation values based on overall coherence (structural constraints). The best global analogy mapping emerges under the pressure of these constraints. Subsequent connectionist models, such as Hummel and Holyoak’s LISA program (1997, 2003), have made significant advances and hold promise for offering a more complete theory of analogical reasoning.

The second example is Hofstadter and Mitchell’s Copycat program (Hofstadter 1995; Mitchell 1993). The program is “designed to discover insightful analogies, and to do so in a psychologically realistic way” (Hofstadter 1995: 205). Copycat operates in the domain of letter-strings. The program handles the following type of problem:

Suppose the letter-string abc were changed to abd ; how would you change the letter-string ijk in “the same way”?

Most people would answer ijl , since it is natural to think that abc was changed to abd by the “transformation rule”: replace the rightmost letter with its successor. Alternative answers are possible, but do not agree with most people’s sense of what counts as the natural analogy.

Hofstadter and Mitchell believe that analogy-making is in large part about the perception of novel patterns, and that such perception requires concepts with “fluid” boundaries. Genuine analogy-making involves “slippage” of concepts. The Copycat program combines a set of core concepts pertaining to letter-sequences ( successor , leftmost and so forth) with probabilistic “halos” that link distinct concepts dynamically. Orderly structures emerge out of random low-level processes and the program produces plausible solutions. Copycat thus shows that analogy-making can be modeled as a process akin to perception, even if the program employs mechanisms distinct from those in human perception.

The multiconstraint theory and Copycat share the idea that analogical cognition involves cognitive processes that operate below the level of abstract reasoning. Both computational models—to the extent that they are capable of performing successful analogical reasoning—challenge the idea that a successful model of analogical reasoning must take the form of a set of quasi-logical criteria. Efforts to develop a quasi-logical theory of analogical reasoning, it might be argued, have failed. In place of faulty inference schemes such as those described earlier ( §2.2 , §2.4 ), computational models substitute procedures that can be judged on their performance rather than on traditional philosophical standards.

In response to this argument, we should recognize the value of the connectionist models while acknowledging that we still need a theory that offers normative principles for evaluating analogical arguments. In the first place, even if the construction and recognition of analogies are largely a matter of perception, this does not eliminate the need for subsequent critical evaluation of analogical inferences. Second and more importantly, we need to look not just at the construction of analogy mappings but at the ways in which individual analogical arguments are debated in fields such as mathematics, physics, philosophy and the law. These high-level debates require reasoning that bears little resemblance to the computational processes of ACME or Copycat. (Ashley’s HYPO (Ashley 1990) is one example of a non-connectionist program that focuses on this aspect of analogical reasoning.) There is, accordingly, room for both computational and traditional philosophical models of analogical reasoning.

3.5.2 Articulation model

Most prominent theories of analogy, philosophical and computational, are based on overall similarity between source and target domains—defined in terms of some favoured subset of Hesse’s horizontal relations (see §2.2 ). Aristotle and Mill, whose approach is echoed in textbook discussions, suggest counting similarities. Hesse’s theory ( §3.3 ) favours “pre-theoretic” correspondences. The structure-mapping theory and its successors ( §3.4 ) look to systematicity, i.e., to correspondences involving complex, high-level networks of relations. In each of these approaches, the problem is twofold: overall similarity is not a reliable guide to plausibility, and it fails to explain the plausibility of any analogical argument.

Bartha’s articulation model (2010) proposes a different approach, beginning not with horizontal relations, but rather with a classification of analogical arguments on the basis of the vertical relations within each domain. The fundamental idea is that a good analogical argument must satisfy two conditions:

Prior Association . There must be a clear connection, in the source domain, between the known similarities (the positive analogy) and the further similarity that is projected to hold in the target domain (the hypothetical analogy). This relationship determines which features of the source are critical to the analogical inference.

Potential for Generalization . There must be reason to think that the same kind of connection could obtain in the target domain. More pointedly: there must be no critical disanalogy between the domains.

The first order of business is to make the prior association explicit. The standards of explicitness vary depending on the nature of this association (causal relation, mathematical proof, functional relationship, and so forth). The two general principles are fleshed out via a set of subordinate models that allow us to identify critical features and hence critical disanalogies.

To see how this works, consider Example 7 (Rectangles and boxes). In this analogical argument, the source domain is two-dimensional geometry: we know that of all rectangles with a fixed perimeter, the square has maximum area. The target domain is three-dimensional geometry: by analogy, we conjecture that of all boxes with a fixed surface area, the cube has maximum volume. This argument should be evaluated not by counting similarities, looking to pre-theoretic resemblances between rectangles and boxes, or constructing connectionist representations of the domains and computing a systematicity score for possible mappings. Instead, we should begin with a precise articulation of the prior association in the source domain, which amounts to a specific proof for the result about rectangles. We should then identify, relative to that proof, the critical features of the source domain: namely, the concepts and assumptions used in the proof. Finally, we should assess the potential for generalization: whether, in the three-dimensional setting, those critical features are known to lack analogues in the target domain. The articulation model is meant to reflect the conversations that can and do take place between an advocate and a critic of an analogical argument.

3.6.1 Norton’s material theory of analogy

As noted in §2.4 , Norton rejects analogical inference rules. But even if we agree with Norton on this point, we might still be interested in having an account that gives us guidelines for evaluating analogical arguments. How does Norton’s approach fare on this score?

According to Norton, each analogical argument is warranted by local facts that must be investigated and justified empirically. First, there is “the fact of the analogy”: in practice, a low-level uniformity that embraces both the source and target systems. Second, there are additional factual properties of the target system which, when taken together with the uniformity, warrant the analogical inference. Consider Galileo’s famous inference ( Example 12 ) that there are mountains on the moon (Galileo 1610). Through his newly invented telescope, Galileo observed points of light on the moon ahead of the advancing edge of sunlight. Noting that the same thing happens on earth when sunlight strikes the mountains, he concluded that there must be mountains on the moon and even provided a reasonable estimate of their height. In this example, Norton tells us, the the fact of the analogy is that shadows and other optical phenomena are generated in the same way on the earth and on the moon; the additional fact about the target is the existence of points of light ahead of the advancing edge of sunlight on the moon.

What are the implications of Norton’s material theory when it comes to evaluating analogical arguments? The fact of the analogy is a local uniformity that powers the inference. Norton’s theory works well when such a uniformity is patent or naturally inferred. It doesn’t work well when the uniformity is itself the target (rather than the driver ) of the inference. That happens with explanatory analogies such as Example 5 (the Acoustical Analogy ), and mathematical analogies such as Example 7 ( Rectangles and Boxes ). Similarly, the theory doesn’t work well when the underlying uniformity is unclear, as in Example 2 ( Life on other Planets ), Example 4 ( Clay Pots ), and many other cases. In short, if Norton’s theory is accepted, then for most analogical arguments there are no useful evaluation criteria.

3.6.2 Field-specific criteria

For those who sympathize with Norton’s skepticism about universal inductive schemes and theories of analogical reasoning, yet recognize that his approach may be too local, an appealing strategy is to move up one level. We can aim for field-specific “working logics” (Toulmin 1958; Wylie and Chapman 2016; Reiss 2015). This approach has been adopted by philosophers of archaeology, evolutionary biology and other historical sciences (Wylie and Chapman 2016; Currie 2013; Currie 2016; Currie 2018). In place of schemas, we find ‘toolkits’, i.e., lists of criteria for evaluating analogical reasoning.

For example, Currie (2016) explores in detail the use of ethnographic analogy ( Example 13 ) between shamanistic motifs used by the contemporary San people and similar motifs in ancient rock art, found both among ancestors of the San (direct historical analogy) and in European rock art (indirect historical analogy). Analogical arguments support the hypothesis that in each of these cultures, rock art symbolizes hallucinogenic experiences. Currie examines criteria that focus on assumptions about stability of cultural traits and environment-culture relationships. Currie (2016, 2018) and Wylie (Wylie and Chapman 2016) also stress the importance of robustness reasoning that combines analogical arguments of moderate strength with other forms of evidence to yield strong conclusions.

Practice-based approaches can thus yield specific guidelines unlikely to be matched by any general theory of analogical reasoning. One caveat is worth mentioning. Field-specific criteria for ethnographic analogy are elicited against a background of decades of methodological controversy (Wylie and Chapman 2016). Critics and defenders of ethnographic analogy have appealed to general models of scientific method (e.g., hypothetico-deductive method or Bayesian confirmation). To advance the methodological debate, practice-based approaches must either make connections to these general models or explain why the lack of any such connection is unproblematic.

3.6.3 Formal analogies in physics

Close attention to analogical arguments in practice can also provide valuable challenges to general ideas about analogical inference. In an interesting discussion, Steiner (1989, 1998) suggests that many of the analogies that played a major role in early twentieth-century physics count as “Pythagorean.” The term is meant to connote mathematical mysticism: a “Pythagorean” analogy is a purely formal analogy, one founded on mathematical similarities that have no known physical basis at the time it is proposed. One example is Schrödinger’s use of analogy ( Example 14 ) to “guess” the form of the relativistic wave equation. In Steiner’s view, Schrödinger’s reasoning relies upon manipulations and substitutions based on purely mathematical analogies. Steiner argues that the success, and even the plausibility, of such analogies “evokes, or should evoke, puzzlement” (1989: 454). Both Hesse (1966) and Bartha (2010) reject the idea that a purely formal analogy, with no physical significance, can support a plausible analogical inference in physics. Thus, Steiner’s arguments provide a serious challenge.

Bartha (2010) suggests a response: we can decompose Steiner’s examples into two or more steps, and then establish that at least one step does, in fact, have a physical basis. Fraser (forthcoming), however, offers a counterexample that supports Steiner’s position. Complex analogies between classical statistical mechanics (CSM) and quantum field theory (QFT) have played a crucial role in the development and application of renormalization group (RG) methods in both theories ( Example 15 ). Fraser notes substantial physical disanalogies between CSM and QFT, and concludes that the reasoning is based entirely on formal analogies.

4. Philosophical foundations for analogical reasoning

What philosophical basis can be provided for reasoning by analogy? What justification can be given for the claim that analogical arguments deliver plausible conclusions? There have been several ideas for answering this question. One natural strategy assimilates analogical reasoning to some other well-understood argument pattern, a form of deductive or inductive reasoning ( §4.1 , §4.2 ). A few philosophers have explored the possibility of a priori justification ( §4.3 ). A pragmatic justification may be available for practical applications of analogy, notably in legal reasoning ( §4.4 ).

Any attempt to provide a general justification for analogical reasoning faces a basic dilemma. The demands of generality require a high-level formulation of the problem and hence an abstract characterization of analogical arguments, such as schema (4). On the other hand, as noted previously, many analogical arguments that conform to schema (4) are bad arguments. So a general justification of analogical reasoning cannot provide support for all arguments that conform to (4), on pain of proving too much. Instead, it must first specify a subset of putatively ‘good’ analogical arguments, and link the general justification to this specified subset. The problem of justification is linked to the problem of characterizing good analogical arguments . This difficulty afflicts some of the strategies described in this section.

Analogical reasoning may be cast in a deductive mold. If successful, this strategy neatly solves the problem of justification. A valid deductive argument is as good as it gets.

An early version of the deductivist approach is exemplified by Aristotle’s treatment of the argument from example ( §3.2 ), the paradeigma . On this analysis, an analogical argument between source domain \(S\) and target \(T\) begins with the assumption of positive analogy \(P(S)\) and \(P(T)\), as well as the additional information \(Q(S)\). It proceeds via the generalization \(\forall x(P(x) \supset Q(x))\) to the conclusion: \(Q(T)\). Provided we can treat that intermediate generalization as an independent premise, we have a deductively valid argument. Notice, though, that the existence of the generalization renders the analogy irrelevant. We can derive \(Q(T)\) from the generalization and \(P(T)\), without any knowledge of the source domain. The literature on analogy in argumentation theory ( §2.2 ) offers further perspectives on this type of analysis, and on the question of whether analogical arguments are properly characterized as deductive.

Some recent analyses follow Aristotle in treating analogical arguments as reliant upon extra (sometimes tacit) premises, typically drawn from background knowledge, that convert the inference into a deductively valid argument––but without making the source domain irrelevant. Davies and Russell introduce a version that relies upon what they call determination rules (Russell 1986; Davies and Russell 1987; Davies 1988). Suppose that \(Q\) and \(P_1 , \ldots ,P_m\) are variables, and we have background knowledge that the value of \(Q\) is determined by the values of \(P_1 , \ldots ,P_m\). In the simplest case, where \(m = 1\) and both \(P\) and \(Q\) are binary Boolean variables, this reduces to

i.e., whether or not \(P\) holds determines whether or not \(Q\) holds. More generally, the form of a determination rule is

i.e., \(Q\) is a function of \(P_1,\ldots\), \(P_m\). If we assume such a rule as part of our background knowledge, then an analogical argument with conclusion \(Q(T)\) is deductively valid. More precisely, and allowing for the case where \(Q\) is not a binary variable: if we have such a rule, and also premises stating that the source \(S\) agrees with the target \(T\) on all of the values \(P_i\), then we may validly infer that \(Q(T) = Q(S)\).

The “determination rule” analysis provides a clear and simple justification for analogical reasoning. Note that, in contrast to the Aristotelian analysis via the generalization \(\forall x(P(x) \supset Q(x))\), a determination rule does not trivialize the analogical argument. Only by combining the rule with information about the source domain can we derive the value of \(Q(T)\). To illustrate by adapting one of the examples given by Russell and Davies ( Example 16 ), let’s suppose that the value \((Q)\) of a used car (relative to a particular buyer) is determined by its year, make, mileage, condition, color and accident history (the variables \(P_i)\). It doesn’t matter if one or more of these factors are redundant or irrelevant. Provided two cars are indistinguishable on each of these points, they will have the same value. Knowledge of the source domain is necessary; we can’t derive the value of the second car from the determination rule alone. Weitzenfeld (1984) proposes a variant of this approach, advancing the slightly more general thesis that analogical arguments are deductive arguments with a missing (enthymematic) premise that amounts to a determination rule.

Do determination rules give us a solution to the problem of providing a justification for analogical arguments? In general: no. Analogies are commonly applied to problems such as Example 8 ( morphine and meperidine ), where we are not even aware of all relevant factors, let alone in possession of a determination rule. Medical researchers conduct drug tests on animals without knowing all attributes that might be relevant to the effects of the drug. Indeed, one of the main objectives of such testing is to guard against reactions unanticipated by theory. On the “determination rule” analysis, we must either limit the scope of such arguments to cases where we have a well-supported determination rule, or focus attention on formulating and justifying an appropriate determination rule. For cases such as animal testing, neither option seems realistic.

Recasting analogy as a deductive argument may help to bring out background assumptions, but it makes little headway with the problem of justification. That problem re-appears as the need to state and establish the plausibility of a determination rule, and that is at least as difficult as justifying the original analogical argument.

Some philosophers have attempted to portray, and justify, analogical reasoning in terms of some well-understood inductive argument pattern. There have been three moderately popular versions of this strategy. The first treats analogical reasoning as generalization from a single case. The second treats it as a kind of sampling argument. The third recognizes the argument from analogy as a distinctive form, but treats past successes as evidence for future success.

4.2.1 Single-case induction

Let’s reconsider Aristotle’s argument from example or paradeigma ( §3.2 ), but this time regard the generalization as justified via induction from a single case (the source domain). Can such a simple analysis of analogical arguments succeed? In general: no.

A single instance can sometimes lead to a justified generalization. Cartwright (1992) argues that we can sometimes generalize from a single careful experiment, “where we have sufficient control of the materials and our knowledge of the requisite background assumptions is secure” (51). Cartwright thinks that we can do this, for example, in experiments with compounds that have stable “Aristotelian natures.” In a similar spirit, Quine (1969) maintains that we can have instantial confirmation when dealing with natural kinds.

Even if we accept that there are such cases, the objection to understanding all analogical arguments as single-case induction is obvious: the view is simply too restrictive. Most analogical arguments will not meet the requisite conditions. We may not know that we are dealing with a natural kind or Aristotelian nature when we make the analogical argument. We may not know which properties are essential. An insistence on the ‘single-case induction’ analysis of analogical reasoning is likely to lead to skepticism (Agassi 1964, 1988).

Interpreting the argument from analogy as single-case induction is also counter-productive in another way. The simplistic analysis does nothing to advance the search for criteria that help us to distinguish between relevant and irrelevant similarities, and hence between good and bad analogical arguments.

4.2.2 Sampling arguments

On the sampling conception of analogical arguments, acknowledged similarities between two domains are treated as statistically relevant evidence for further similarities. The simplest version of the sampling argument is due to Mill (1843/1930). An argument from analogy, he writes, is “a competition between the known points of agreement and the known points of difference.” Agreement of \(A\) and \(B\) in 9 out of 10 properties implies a probability of 0.9 that \(B\) will possess any other property of \(A\): “we can reasonably expect resemblance in the same proportion” (367). His only restriction has to do with sample size: we must be relatively knowledgeable about both \(A\) and \(B\). Mill saw no difficulty in using analogical reasoning to infer characteristics of newly discovered species of plants or animals, given our extensive knowledge of botany and zoology. But if the extent of unascertained properties of \(A\) and \(B\) is large, similarity in a small sample would not be a reliable guide; hence, Mill’s dismissal of Reid’s argument about life on other planets ( Example 2 ).

The sampling argument is presented in more explicit mathematical form by Harrod (1956). The key idea is that the known properties of \(S\) (the source domain) may be considered a random sample of all \(S\)’s properties—random, that is, with respect to the attribute of also belonging to \(T\) (the target domain). If the majority of known properties that belong to \(S\) also belong to \(T\), then we should expect most other properties of \(S\) to belong to \(T\), for it is unlikely that we would have come to know just the common properties. In effect, Harrod proposes a binomial distribution, modeling ‘random selection’ of properties on random selection of balls from an urn.

There are grave difficulties with Harrod’s and Mill’s analyses. One obvious difficulty is the counting problem : the ‘population’ of properties is poorly defined. How are we to count similarities and differences? The ratio of shared to total known properties varies dramatically according to how we do this. A second serious difficulty is the problem of bias : we cannot justify the assumption that the sample of known features is random. In the case of the urn, the selection process is arranged so that the result of each choice is not influenced by the agent’s intentions or purposes, or by prior choices. By contrast, the presentation of an analogical argument is always partisan. Bias enters into the initial representation of similarities and differences: an advocate of the argument will highlight similarities, while a critic will play up differences. The paradigm of repeated selection from an urn seems totally inappropriate. Additional variations of the sampling approach have been developed (e.g., Russell 1988), but ultimately these versions also fail to solve either the counting problem or the problem of bias.

4.2.3 Argument from past success

Section 3.6 discussed Steiner’s view that appeal to ‘Pythagorean’ analogies in physics “evokes, or should evoke, puzzlement” (1989: 454). Liston (2000) offers a possible response: physicists are entitled to use Pythagorean analogies on the basis of induction from their past success:

[The scientist] can admit that no one knows how [Pythagorean] reasoning works and argue that the very fact that similar strategies have worked well in the past is already reason enough to continue pursuing them hoping for success in the present instance. (200)

Setting aside familiar worries about arguments from success, the real problem here is to determine what counts as a similar strategy. In essence, that amounts to isolating the features of successful Pythagorean analogies. As we have seen (§2.4), nobody has yet provided a satisfactory scheme that characterizes successful analogical arguments, let alone successful Pythagorean analogical arguments.

An a priori approach traces the validity of a pattern of analogical reasoning, or of a particular analogical argument, to some broad and fundamental principle. Three such approaches will be outlined here.

The first is due to Keynes (1921). Keynes appeals to his famous Principle of the Limitation of Independent Variety, which he articulates as follows:

Armed with this Principle and some additional assumptions, Keynes is able to show that in cases where there is no negative analogy , knowledge of the positive analogy increases the (logical) probability of the conclusion. If there is a non-trivial negative analogy, however, then the probability of the conclusion remains unchanged, as was pointed out by Hesse (1966). Those familiar with Carnap’s theory of logical probability will recognize that in setting up his framework, Keynes settled on a measure that permits no learning from experience.

Hesse offers a refinement of Keynes’s strategy, once again along Carnapian lines. In her (1974), she proposes what she calls the Clustering Postulate : the assumption that our epistemic probability function has a built-in bias towards generalization. The objections to such postulates of uniformity are well-known (see Salmon 1967), but even if we waive them, her argument fails. The main objection here—which also applies to Keynes—is that a purely syntactic axiom such as the Clustering Postulate fails to discriminate between analogical arguments that are good and those that are clearly without value (according to Hesse’s own material criteria, for example).

A different a priori strategy, proposed by Bartha (2010), limits the scope of justification to analogical arguments that satisfy tentative criteria for ‘good’ analogical reasoning. The criteria are those specified by the articulation model ( §3.5 ). In simplified form, they require the existence of non-trivial positive analogy and no known critical disanalogy. The scope of Bartha’s argument is also limited to analogical arguments directed at establishing prima facie plausibility, rather than degree of probability.

Bartha’s argument rests on a principle of symmetry reasoning articulated by van Fraassen (1989: 236): “problems which are essentially the same must receive essentially the same solution.” A modal extension of this principle runs roughly as follows: if problems might be essentially the same, then they might have essentially the same solution. There are two modalities here. Bartha argues that satisfaction of the criteria of the articulation model is sufficient to establish the modality in the antecedent, i.e., that the source and target domains ‘might be essentially the same’ in relevant respects. He further suggests that prima facie plausibility provides a reasonable reading of the modality in the consequent, i.e., that the problems in the two domains ‘might have essentially the same solution.’ To call a hypothesis prima facie plausible is to elevate it to the point where it merits investigation, since it might be correct.

The argument is vulnerable to two sorts of concerns. First, there are questions about the interpretation of the symmetry principle. Second, there is a residual worry that this justification, like all the others, proves too much. The articulation model may be too vague or too permissive.

Arguably, the most promising available defense of analogical reasoning may be found in its application to case law (see Precedent and Analogy in Legal Reasoning ). Judicial decisions are based on the verdicts and reasoning that have governed relevantly similar cases, according to the doctrine of stare decisis (Levi 1949; Llewellyn 1960; Cross and Harris 1991; Sunstein 1993). Individual decisions by a court are binding on that court and lower courts; judges are obligated to decide future cases ‘in the same way.’ That is, the reasoning applied in an individual decision, referred to as the ratio decidendi , must be applied to similar future cases (see Example 10 ). In practice, of course, the situation is extremely complex. No two cases are identical. The ratio must be understood in the context of the facts of the original case, and there is considerable room for debate about its generality and its applicability to future cases. If a consensus emerges that a past case was wrongly decided, later judgments will distinguish it from new cases, effectively restricting the scope of the ratio to the original case.

The practice of following precedent can be justified by two main practical considerations. First, and above all, the practice is conservative : it provides a relatively stable basis for replicable decisions. People need to be able to predict the actions of the courts and formulate plans accordingly. Stare decisis serves as a check against arbitrary judicial decisions. Second, the practice is still reasonably progressive : it allows for the gradual evolution of the law. Careful judges distinguish bad decisions; new values and a new consensus can emerge in a series of decisions over time.

In theory, then, stare decisis strikes a healthy balance between conservative and progressive social values. This justification is pragmatic. It pre-supposes a common set of social values, and links the use of analogical reasoning to optimal promotion of those values. Notice also that justification occurs at the level of the practice in general; individual analogical arguments sometimes go astray. A full examination of the nature and foundations for stare decisis is beyond the scope of this entry, but it is worth asking the question: might it be possible to generalize the justification for stare decisis ? Is a parallel pragmatic justification available for analogical arguments in general?

Bartha (2010) offers a preliminary attempt to provide such a justification by shifting from social values to epistemic values. The general idea is that reasoning by analogy is especially well suited to the attainment of a common set of epistemic goals or values. In simple terms, analogical reasoning—when it conforms to certain criteria—achieves an excellent (perhaps optimal) balance between the competing demands of stability and innovation. It supports both conservative epistemic values, such as simplicity and coherence with existing belief, and progressive epistemic values, such as fruitfulness and theoretical unification (McMullin (1993) provides a classic list).

5. Beyond analogical arguments

As emphasized earlier, analogical reasoning takes in a great deal more than analogical arguments. In this section, we examine two broad contexts in which analogical reasoning is important.

The first, still closely linked to analogical arguments, is the confirmation of scientific hypotheses. Confirmation is the process by which a scientific hypothesis receives inductive support on the basis of evidence (see evidence , confirmation , and Bayes’ Theorem ). Confirmation may also signify the logical relationship of inductive support that obtains between a hypothesis \(H\) and a proposition \(E\) that expresses the relevant evidence. Can analogical arguments play a role, either in the process or in the logical relationship? Arguably yes (to both), but this role has to be delineated carefully, and several obstacles remain in the way of a clear account.

The second context is conceptual and theoretical development in cutting-edge scientific research. Analogies are used to suggest possible extensions of theoretical concepts and ideas. The reasoning is linked to considerations of plausibility, but there is no straightforward analysis in terms of analogical arguments.

How is analogical reasoning related to the confirmation of scientific hypotheses? The examples and philosophical discussion from earlier sections suggest that a good analogical argument can indeed provide support for a hypothesis. But there are good reasons to doubt the claim that analogies provide actual confirmation.

In the first place, there is a logical difficulty. To appreciate this, let us concentrate on confirmation as a relationship between propositions. Christensen (1999: 441) offers a helpful general characterization:

Some propositions seem to help make it rational to believe other propositions. When our current confidence in \(E\) helps make rational our current confidence in \(H\), we say that \(E\) confirms \(H\).

In the Bayesian model, ‘confidence’ is represented in terms of subjective probability. A Bayesian agent starts with an assignment of subjective probabilities to a class of propositions. Confirmation is understood as a three-place relation:

\(E\) represents a proposition about accepted evidence, \(H\) stands for a hypothesis, \(K\) for background knowledge and \(Pr\) for the agent’s subjective probability function. To confirm \(H\) is to raise its conditional probability, relative to \(K\). The shift from prior probability \(Pr(H \mid K)\) to posterior probability \(Pr(H \mid E \cdot K)\) is referred to as conditionalization on \(E\). The relation between these two probabilities is typically given by Bayes’ Theorem (setting aside more complex forms of conditionalization):

For Bayesians, here is the logical difficulty: it seems that an analogical argument cannot provide confirmation. In the first place, it is not clear that we can encapsulate the information contained in an analogical argument in a single proposition, \(E\). Second, even if we can formulate a proposition \(E\) that expresses that information, it is typically not appropriate to treat it as evidence because the information contained in \(E\) is already part of the background, \(K\). This means that \(E \cdot K\) is equivalent to \(K\), and hence \(Pr(H \mid E \cdot K) = Pr(H \mid K)\). According to the Bayesian definition, we don’t have confirmation. (This is a version of the problem of old evidence; see confirmation .) Third, and perhaps most important, analogical arguments are often applied to novel hypotheses \(H\) for which the prior probability \(Pr(H \mid K)\) is not even defined. Again, the definition of confirmation in terms of Bayesian conditionalization seems inapplicable.

If analogies don’t provide inductive support via ordinary conditionalization, is there an alternative? Here we face a second difficulty, once again most easily stated within a Bayesian framework. Van Fraassen (1989) has a well-known objection to any belief-updating rule other than conditionalization. This objection applies to any rule that allows us to boost credences when there is no new evidence. The criticism, made vivid by the tale of Bayesian Peter, is that these ‘ampliative’ rules are vulnerable to a Dutch Book . Adopting any such rule would lead us to acknowledge as fair a system of bets that foreseeably leads to certain loss. Any rule of this type for analogical reasoning appears to be vulnerable to van Fraassen’s objection.

There appear to be at least three routes to avoiding these difficulties and finding a role for analogical arguments within Bayesian epistemology. First, there is what we might call minimal Bayesianism . Within the Bayesian framework, some writers (Jeffreys 1973; Salmon 1967, 1990; Shimony 1970) have argued that a ‘seriously proposed’ hypothesis must have a sufficiently high prior probability to allow it to become preferred as the result of observation. Salmon has suggested that analogical reasoning is one of the most important means of showing that a hypothesis is ‘serious’ in this sense. If analogical reasoning is directed primarily towards prior probability assignments, it can provide inductive support while remaining formally distinct from confirmation, avoiding the logical difficulties noted above. This approach is minimally Bayesian because it provides nothing more than an entry point into the Bayesian apparatus, and it only applies to novel hypotheses. An orthodox Bayesian, such as de Finetti (de Finetti and Savage 1972, de Finetti 1974), might have no problem in allowing that analogies play this role.

The second approach is liberal Bayesianism : we can change our prior probabilities in a non-rule-based fashion . Something along these lines is needed if analogical arguments are supposed to shift opinion about an already existing hypothesis without any new evidence. This is common in fields such as archaeology, as part of a strategy that Wylie refers to as “mobilizing old data as new evidence” (Wylie and Chapman 2016: 95). As Hawthorne (2012) notes, some Bayesians simply accept that both initial assignments and ongoing revision of prior probabilities (based on plausibility arguments) can be rational, but

the logic of Bayesian induction (as described here) has nothing to say about what values the prior plausibility assessments for hypotheses should have; and it places no restrictions on how they might change.

In other words, by not stating any rules for this type of probability revision, we avoid the difficulties noted by van Fraassen. This approach admits analogical reasoning into the Bayesian tent, but acknowledges a dark corner of the tent in which rationality operates without any clear rules.

Recently, a third approach has attracted interest: analogue confirmation or confirmation via analogue simulation . As described in (Dardashti et al. 2017), the idea is as follows:

Our key idea is that, in certain circumstances, predictions concerning inaccessible phenomena can be confirmed via an analogue simulation in a different system. (57)

Dardashti and his co-authors concentrate on a particular example ( Example 17 ): ‘dumb holes’ and other analogues to gravitational black holes (Unruh 1981; Unruh 2008). Unlike real black holes, some of these analogues can be (and indeed have been) implemented and studied in the lab. Given the exact formal analogy between our models for these systems and our models of black holes, and certain important additional assumptions, Dardashti et al. make the controversial claim that observations made about the analogues provide evidence about actual black holes. For instance, the observation of phenomena analogous to Hawking radiation in the analogue systems would provide confirmation for the existence of Hawking radiation in black holes. In a second paper (Dardashti et al. 2018, Other Internet Resources), the case for confirmation is developed within a Bayesian framework.

The appeal of a clearly articulated mechanism for analogue confirmation is obvious. It would provide a tool for exploring confirmation of inaccessible phenomena not just in cosmology, but also in historical sciences such as archaeology and evolutionary biology, and in areas of medical science where ethical constraints rule out experiments on human subjects. Furthermore, as noted by Dardashti et al., analogue confirmation relies on new evidence obtained from the analogue system, and is therefore not vulnerable to the logical difficulties noted above.

Although the concept of analogue confirmation is not entirely new (think of animal testing, as in Example 8 ), the claims of (Dardashti et al. 2017, 2018 [Other Internet Resources]) require evaluation. One immediate difficulty for the black hole example: if we think in terms of ordinary analogical arguments, there is no positive analogy because, to put it simply, we have no basis of known similarities between a ‘dumb hole’ and a black hole. As Crowther et al. (2018, Other Internet Resources) argue, “it is not known if the particular modelling framework used in the derivation of Hawking radiation actually describes black holes in the first place. ” This may not concern Dardashti et al., since they claim that analogue confirmation is distinct from ordinary analogical arguments. It may turn out that analogue confirmation is different for cases such as animal testing, where we have a basis of known similarities, and for cases where our only access to the target domain is via a theoretical model.

In §3.6 , we saw that practice-based studies of analogy provide insight into the criteria for evaluating analogical arguments. Such studies also point to dynamical or programmatic roles for analogies, which appear to require evaluative frameworks that go beyond those developed for analogical arguments.

Knuttila and Loettgers (2014) examine the role of analogical reasoning in synthetic biology, an interdisciplinary field that draws on physics, chemistry, biology, engineering and computational science. The main role for analogies in this field is not the construction of individual analogical arguments but rather the development of concepts such as “noise” and “feedback loops”. Such concepts undergo constant refinement, guided by both positive and negative analogies to their analogues in engineered and physical systems. Analogical reasoning here is “transient, heterogeneous, and programmatic” (87). Negative analogies, seen as problematic obstacles for individual analogical arguments, take on a prominent and constructive role when the focus is theoretical construction and concept refinement.

Similar observations apply to analogical reasoning in its application to another cutting-edge field: emergent gravity. In this area of physics, distinct theoretical approaches portray gravity as emerging from different microstructures (Linneman and Visser 2018). “Novel and robust” features not present at the micro-level emerge in the gravitational theory. Analogies with other emergent phenomena, such as hydrodynamics and thermodynamics, are exploited to shape these proposals. As with synthetic biology, analogical reasoning is not directed primarily towards the formulation and assessment of individual arguments. Rather, its role is to develop different theoretical models of gravity.

These studies explore fluid and creative applications of analogy to shape concepts on the front lines of scientific research. An adequate analysis would certainly take us beyond the analysis of individual analogical arguments, which have been the focus of our attention. Knuttila and Loettgers (2014) are led to reject the idea that the individual analogical argument is the “primary unit” in analogical reasoning, but this is a debatable conclusion. Linneman and Visser (2018), for instance, explicitly affirm the importance of assessing the case for different gravitational models through “exemplary analogical arguments”:

We have taken up the challenge of making explicit arguments in favour of an emergent gravity paradigm… That arguments can only be plausibility arguments at the heuristic level does not mean that they are immune to scrutiny and critical assessment tout court. The philosopher of physics’ job in the process of discovery of quantum gravity… should amount to providing exactly this kind of assessments. (Linneman and Visser 2018: 12)

Accordingly, Linneman and Visser formulate explicit analogical arguments for each model of emergent gravity, and assess them using familiar criteria for evaluating individual analogical arguments. Arguably, even the most ambitious heuristic objectives still depend upon considerations of plausibility that benefit by being expressed, and examined, in terms of analogical arguments.

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How to cite this entry . Preview the PDF version of this entry at the Friends of the SEP Society . Look up topics and thinkers related to this entry at the Internet Philosophy Ontology Project (InPhO). Enhanced bibliography for this entry at PhilPapers , with links to its database.

Other Internet Resources

• Crowther, K., N. Linnemann, and C. Wüthrich, 2018, “ What we cannot learn from analogue experiments ,” online at arXiv.org.
• Dardashti, R., S. Hartmann, K. Thébault, and E. Winsberg, 2018, “ Hawking Radiation and Analogue Experiments: A Bayesian Analysis ,” online at PhilSci Archive.
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• Resources for Research on Analogy: a Multi-Disciplinary Guide (University of Windsor)
• UCLA Reasoning Lab (UCLA)
• Dedre Gentner’s publications (Northwestern University)
• The Center for Research on Concepts and Cognition (Indiana University)

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Part Six: Evaluating Inductive Logic

Chapter Fifteen: Arguments from Analogy

Arguments that make their point by means of similarities are impostors, and, unless you are on your guard against them, will quite readily deceive you. —Plato

Analogies decide nothing, that is true, but they can make one feel more at home. —Sigmund Freud, New Introductory Lectures on Psychoanalysis

Correct Form for Arguments from Analogy

• The Total Evidence Condition (1): Relevant Similarities
• The Total Evidence Condition (2): Irrelevant Dissimilarities
• The Special Character of Arguments from Analogy

Arguments from analogy declare that because two items are the same in one respect they are the same in another. As Freud notes, they can make you feel at home—and for that reason they can be especially persuasive.

During World War I, the Socialist Party distributed leaflets to recent draftees, urging them to oppose the draft. The draft, they contended, violated the constitutional amendment against involuntary servitude. Oliver Wendell Holmes, chief justice of the Supreme Court, argued that they did not have the right to circulate the leaflets during wartime. The right to free speech, he asserted, “would not protect a man in falsely shouting fire in a theater and causing a panic.” Since in both cases “the words used . . . create a clear and present danger,” he concluded, the right to free speech did not protect the Socialists in expressing ideas that might harm the war effort. The argument begins with something familiar—of course we don’t have the right to falsely shout fire in a theater—and invites us to conclude the same about something less familiar—under certain circumstances we don’t even have the right to explain to others our interpretation of the U.S. Constitution. (Holmes is often quoted as calling it “a crowded theater.” He didn’t, though it is probably what he had in mind.)

Arguments from analogy are almost always enticing because, by their very nature, they use two of the quick-and-dirty shortcuts in reasoning described in Chapter 1. By beginning with the familiar, they exploit our dependence on the vividness shortcut; and by presenting similarities between the familiar and the unfamiliar, they take advantage of our dependence on the similarity shortcut. They are custom-made for the way our minds naturally operate. This makes us especially susceptible to them and heightens the importance of being able to evaluate them effectively.

15.1 Correct Form for Arguments from Analogy

Analogies are often used merely for rhetorical effect. Acel Moore of the Philadelphia Inquirer, for example, writes: “Writing editorials is a lot like wearing a navy blue suit and standing in a rainstorm on a cold day and wetting your pants; it may give you a warm feeling for a minute, but no one else is going to notice.” Moore doesn’t attempt to establish any conclusion based on the similarity—he simply makes note of it. Don’t jump to the conclusion that an analogy introduces an argument unless there really is—at least implicitly—a conclusion.

When there is an argument from analogy , as in the preceding free speech argument, it can typically be clarified according to the following form:

• A is F and G.

A and B, as always, are used here as name letters. They name the two analogs [1] —that is, the two things (or classes of things) that are said to be analogous. A, the basic analog , is the one that we are presumed to be more familiar with; in the free speech argument it is falsely shouting fire in a theater. B, the inferred analog , is the thing in question, the one that the argument draws a conclusion about; in the free speech argument it is expressing ideas that might harm the war effort.

We will continue to use F and G as property letters. F is the basic similarity , the property that the two analogs share, presumably without controversy. In the free speech argument, the basic similarity is that they create a clear and present danger. And G is the inferred similarity , the property that the inferred analog is purported to have on the grounds that the basic analog has it. Is not protected by the right to free speech is the inferred similarity in the free speech argument. Here is one good way to clarify the argument:

• Falsely shouting fire in a theater creates a clear and present danger and is not protected by the right to free speech.
• Expressing ideas that might harm the war effort creates a clear and present danger.
• ∴ Expressing ideas that might harm the war effort is not protected by the right to free speech..

Variations on this model are common. The basic or inferred analog, for example, will sometimes include more than one item, as in this example:

Manatees must be mammals, since whales and dolphins, like manatees, are sea creatures that give live birth, and whales and dolphins are definitely mammals.

In this case, the basic analog—the content of A —is whales and dolphins.

Likewise, either the basic similarity or the inferred similarity may include more than one property, as in this example:

Manatees must be mammals, since whales, like manatees, are sea creatures that give live birth and that nourish their young on the mother’s milk, and whales are definitely mammals.

In this example, the basic similarity—the content of F —is sea creatures that give live birth and nourish their young on the mother’s milk.

Clarifying an argument from analogy is usually a straightforward matter. It is easiest to begin by identifying the analogs—the two items that the arguer is comparing; insert the one that is not in question into the A position as the basic analog, and the one that is in question into the B position, as the inferred analog. Then insert the basic similarity—the property the two analogs uncontroversially share—into both premises as F. Finally, insert the inferred similarity into the first premise and the conclusion, as G.

Arguments from analogy are sometimes enthymemes. When there is an implicit statement, it is usually the second premise, the one that establishes the basic similarity. This is because arguers often assume, rightly, that the similarity between two analogs is so obvious that it goes without saying. Suppose I say to a friend of mine, whose son is about to enter first grade, “Since John behaves respectfully towards his parents, he will surely treat his teachers with respect.” The basic analog is John’s parents, the inferred analog is John’s teachers, and the inferred similarity is are treated with respect by John. But what is the basic similarity? We must identify a relevant trait that parents and teachers have in common, namely, that they are authority figures to John. Here is the clarified argument. (Brackets, as usual, indicate that premise 2 is implicit, but we also must supply to premise 1 the part about authority figures.)

• John’s parents are authority figures to him and are treated with respect by him.
• [John’s teachers will be authority figures to him.]
• ∴ John’s teachers will be treated with respect by him.

EXERCISES Chapter 15, set (a)

For each of these arguments from analogy, identify the basic analog, the inferred analog, the basic similarity, and the inferred similarity. Then clarify it in standard clarifying format.

Sample exercise. “Expressions of shock and sadness came from other coaches and administrators following the announcement by Tulane President Eamon Kelly that the school planned to drop its basketball program in the wake of the alleged gambling scheme and newly discovered NCAA violations. Coach Jim Killingsworth of TCU said: ‘I think they should deal with the problem, not do away with it. If they had something like that happen in the English department, would they do away with that? I feel like they should have tried to solve their problems.’” —Associated Press

Sample answer. Basic analog: English department. Inferred analog: basketball program. Basic similarity: is a college program (implicit). Inferred similarity: should not be eliminated if experiencing problems.

• The English department is a college program and should not be eliminated if it is experiencing problems.
• [The basketball program is a college program.]
• ∴ The basketball program should not be eliminated if it is experiencing problems.
• In a good marriage, partners often seek counseling to help them resolve their difficulties. You’re having trouble with your boss—why should a conflict in an employer–employee relationship be treated any differently?
• So you got tickets to the Metropolitan Opera’s production of the “Flying Dutchman”? You should try to smuggle in a flashlight and a good book. I made the mistake of going to Wagner’s “Parsifal”—that night was one of the most boring years of my life.
• Etiquette arbiter Emily Post contended that men need not remove their hats in elevators when there are women present. She reasoned that an elevator is a means of transportation, just like a streetcar, bus, subway, or train. The only difference is that an elevator travels vertically, rather than horizontally. A man is not expected to remove his hat in other vehicles, so there is no need for him to do so in an elevator.
• View expressed in a mid-20th century article by a professional sociologist: One attribute with which women are naturally and uniquely gifted is the care of children. Since the ill and infirm resemble children in many ways, being not merely physically weak and helpless but also psychologically dependent, it is fairly easy to conclude that women are also especially qualified to care for the sick.
• “Suppose you had a son, a fine writer who had brought national recognition for his college newspaper and a scholarship for himself. Suppose that, in his junior year, a big-city newspaper offered him a reporter’s job with a three-year guarantee at an unheard-of salary. Would you advise him to turn down the offer of a professional newspaper job? We know the answer. And we would not think twice before urging him, begging him, to hire on with the newspaper. After all, we’d say, the reason he was in college was to start to prepare himself for a decent career in the field of his choosing. So, why all the fulmination about a star athlete’s taking the chance to make himself a cool $5 million by doing for pay what he’s been doing for free (presumably) for three years?” —William Raspberry, Los Angeles Times
• “We feel instinctive sympathy for the defendant who pleads, ‘I tried to get a job and nobody would hire me. Only in desperation did I turn to robbery.’ Now consider the logically parallel defense: ‘I tried to seduce a woman legitimately and nobody would sleep with me. Only in desperation did I turn to rape.’ Nobody would buy that from a rapist, and nobody should buy it from a robber.” —Steven Landsburg, Forbes

15.2 The Total Evidence Condition (1): Relevant Similarities

If an argument from analogy can be loyally paraphrased in the form described above, then it satisfies the correct form condition. But for an inductive argument to be logically strong it must not only satisfy the correct form condition; it must also satisfy the total evidence condition. As with frequency arguments and inductive generalizations, there are two parts to the total evidence condition for arguments from analogy: the basic similarity must be relevant, and any dissimilarities must be irrelevant. If an argument does poorly on either one of these conditions, it should be judged no better than logically weak.

Although analogical arguments are sometimes accused of committing the fallacy of false analogy (or the fallacy of faulty analogy ), this fallacy is very much like the fallacy of hasty generalization. The existence of the named fallacy highlights the ease with which we can make mistakes in this sort of reasoning. But to accuse an argument from analogy of committing this fallacy says nothing about what has gone wrong with the argument. It is far better to explain more specifically how it is that some necessary condition for soundness has not been satisfied.

Total Evidence Condition for Arguments from Analogy

• The basic similarity must be relevant —it must count in favor of the inferred similarity.
• The dissimilarities must be irrelevant —any dissimilarity between the two analogs must not make the basic analog a better candidate for the inferred property.

The argument is logically weaker to the extent that it fails in either area.

15.2.1 The Relevance of the Basic Similarity

Begin your deliberations about the total evidence question by asking, Is the basic similarity relevant? The more relevant it is, the stronger the logic of the argument might be. When you consider this question, forget about the two analogs and simply consider to what extent the basic similarity counts in favor of the inferred similarity. A television advertising campaign by a dairy company shows old but cheerful citizens of the Republic of Georgia eating yogurt; they have eaten yogurt all their lives, we are told, and they are now well past the century mark—one woman is now 134! Eating yogurt, we are encouraged to believe, could do the same for us. The first step in evaluating how well this argument satisfies the total evidence condition is to ignore the two analogs (citizens of Georgia and us) and ask whether the basic similarity—eating yogurt—counts in favor of the inferred similarity—a long life. There is no special reason to think so, and the argument doesn’t help by providing one. So the logic of the argument is very weak.

More commonly an argument from analogy satisfies the condition at least to some degree. One large state university published the following story in its alumni magazine:

A preliminary appraisal of the results of a major assessment of faculty and graduate programs conducted by the Conference Board of Associated Research Councils placed our institution second in the nation among public research universities and in the top five overall. “It is gratifying to see our faculty receive this national recognition of their superior research and teaching,” said the Chancellor. Even though the study focused on graduate programs, he pointed out that the results could also be applied to the undergraduate program as well, since the two programs share the same faculty.

The university’s graduate program is the basic analog and its undergraduate program the inferred analog. The basic similarity is that the university’s excellent faculty staffs them. And the inferred similarity is that the academic programs are excellent. Is the basic similarity relevant? That is, does having an excellent faculty count toward the excellent academic programs? Of course it does. So this argument easily clears the first hurdle of the total evidence condition. But it is too soon to conclude that the argument is logically strong; there is still a second total evidence hurdle to clear.

15.2.2 Relevant Similarities and the Fallacy of Equivocation

Suppose I say, “Einstein was smart, and he was able to revolutionize physics. The physics teacher I had in high school is smart, too, so he should be able to revolutionize physics.” The basic similarity is relevant to the inferred similarity—smart is better than stupid when it comes to revolutionizing physics. But there is smart, and then there is smart. Surely my high school physics teacher is not as smart as Einstein. Doesn’t that weaken the argument? Let’s clarify it and see:

• Einstein was smart and was able to revolutionize physics.
• My high school physics teacher is smart.
• ∴ My high school physics teacher is able to revolutionize physics.

Smart shows up in both premises. To ask whether my high school physics teacher is as smart as Einstein is to ask, in effect, whether the word means the same thing in each case. It is a general expression. Recalling our coverage of generality in Chapter 5, this means that it is an expression that allows for degrees (examples were fine, bald, brown, living together, incompatible, wrong, and evil ). As we saw, generality is usually unproblematic. It becomes problematic, however, when the meaning of the expression shifts from one use to the next, and when the apparent success of the argument depends on that shift. In that case, the argument commits the fallacy of equivocation; the lesson from Chapter 5 is to eliminate the ambiguity.

Let’s eliminate the ambiguity by using the reasonable-premises approach in revising premise 2; in that case it is as follows:

2. My high school physics teacher is smart, though not as smart as Einstein.

While this is probably true, we now have a major problem with the logic of the argument—namely, it no longer satisfies the correct form condition, since the basic similarity, established in premise 1, is not asserted in premise 2. (The form is now something like this: 1. A is F and G; 2. B is sort of like F ; ∴ C . B is G. ) Let’s try revising it again, this time using the reasonable-logic approach. This gives us the following:

2. My high school physics teacher is just as smart as Einstein.

This nicely fixes the logical problem, but at the cost of what is pretty obviously a false premise. Either way, the argument is unsound.

The Oliver Wendell Holmes free speech argument, presented at the beginning of the chapter, provides a weightier example of the same problem. The basic similarity, creating a clear and present danger, certainly counts in favor of the inferred similarity of not being protected by the right to free speech. But is the danger caused by the wartime expression of potentially subversive ideas as clear and as present as the danger caused by the false shout of fire in a theater? If not, doesn’t this weaken the argument? Let’s take another look at Holmes’s clarified argument.

• ∴ Expressing ideas that might harm the war effort is not protected by the right to free speech.

The phrase clear and present danger, like the term smart in the Einstein example, is a general term that seems to apply to a greater degree in premise 1 than in premise 2. It is plausible to suppose that this shift contributes to the apparent success of the argument, and thus that the argument commits the fallacy of equivocation. So we should revise our paraphrase of premise 2 to eliminate the ambiguity. On the one hand, we could paraphrase it to say that those who scattered the leaflets created a clear and present danger, though less clear and present than falsely shouting fire in a theater. The premise would probably be true, but we would have created the same logical difficulty described in the Einstein argument—the basic similarity is not the same in each premise. On the other hand, we could paraphrase it to say that they created a clear and present danger that is just as clear and present as falsely shouting fire in a theater. We have now satisfied the correct form condition but probably have a false premise.

The problem is one to look for whenever you are clarifying an argument from analogy.

EXERCISES Chapter 15, set (b)

For each of the arguments in set (a), answer whether the basic similarity is relevant.

Sample exercise. See sample in set (a).

Sample answer. The basic similarity (that something is a college program) has some relevance to the inferred similarity (that it shouldn’t be eliminated if it is experiencing problems), but only to a limited extent. It is relevant only insofar as there is some weak presumption in any sort of institution that a program that has been set up was set up for a good reason.

15.3 The Total Evidence Condition (2): Irrelevant Dissimilarities

15.3.1 the irrelevance of the dissimilarities.

The second total evidence question is Are there relevant dissimilarities? Preferably they are irrelevant, for the more relevant the dissimilarities, the weaker the logic of the argument. When you consider this question, forget about the basic similarity and concentrate on the two analogs. There are always innumerable ways in which they are dissimilar, but most or all of them will be irrelevant. What matters is to what extent any dissimilarity makes the basic analog a better candidate for the inferred property.

Consider, for example, the free speech argument. There are many dissimilarities. One of the activities happens in a theater, for example, while the other could happen anywhere; but this is irrelevant, since there is no reason to think that things said in a theater are less deserving of protection by the right to free speech than things said anywhere else. Or, for example, one of them is spoken aloud, while the other could be written down; but again, this is irrelevant, for there is no general reason to think that the spoken word is more worthy of free speech protection than the written word.

Some of the dissimilarities, however, are relevant. In the theater case, what is expressed is intentionally deceptive, while in the leaflet case, what is expressed seems to have been utterly sincere. This, taken by itself, certainly makes the theater case a better candidate for exemption from free speech protection, and thus it counts as a relevant dissimilarity. Furthermore, in the theater case, the action is sure to have a harmful result; but in the leaflet case, there is no assurance that anyone will pay any attention or, if they do, that they will be influenced (in fact, it was established that no one had been persuaded by the leaflet). This, too, makes the theater case a better candidate for lack of protection by the right to free speech.

In short, even if we forget that the phrase clear and present danger may be equivocal, the argument does not score well on the second portion of the total evidence condition. Its logic can be judged, at best, as fairly weak. Brilliant jurist that he was, I should note that Oliver Wendell Holmes relied, as he should have, on a good deal more than just this argument in support of his conclusion.

Let’s now return to the academic excellence argument. Here is the clarification:

• The university’s graduate program is staffed by the university’s faculty and is academically excellent.
• The university’s undergraduate program is staffed by the university’s faculty.
• ∴ The university’s undergraduate program is academically excellent.

There are many dissimilarities between the graduate and undergraduate programs of any large state university. Graduate courses, for example, are usually assigned higher catalog numbers than are undergraduate courses. But this is irrelevant; catalog numbers are not like scores flashed by Olympic judges, with higher numbers going to better courses. Another difference is that in large state universities the graduate students tend to have much more exposure to the faculty than do the undergraduate students—their classes are much smaller and are more frequently taught by the regular faculty members. This is relevant, since student exposure to faculty can contribute powerfully to academic excellence. The conclusion may still be true. But even though this argument does well on the first condition, it performs badly on the second and so its logic must be considered weak.

EXERCISES Chapter 15, set (c)

For each of the arguments in set (a), do three things: ( i ) state an irrelevant dissimilarity, and explain, ( ii ) explain any relevant dissimilarities, and ( iii ) state your evaluation of the argument’s logic based on this and the previous exercise.

Sample answer. ( i ) The basketball program probably has a higher proportion of students on full scholarship than does the English department. This doesn’t seem relevant, since it doesn’t make English a better candidate for preservation in the face of difficulties. ( ii ) The most important dissimilarity is that the English department is not only an academic program, but also one that is central to the mission of the institution, while the basketball program is an athletic program and thus more peripheral to its mission. This means there is a far stronger impetus to work out English department difficulties before disbanding it. ( iii ) Though the argument is OK on the first part of the total evidence condition, it fails the second part and is logically very weak.

15.4 The Special Character of Arguments from Analogy

15.4.1 arguments from analogy as logical borrowers.

As you may have noticed, every example of an argument from analogy worked out in this chapter has been declared logically weak and thus unsound. This is not an aberration. Although not all arguments from analogy are unsound, they do establish their conclusions far less often than any other sort of argument. Plato, in the lead quotation for this chapter, calls them “impostors.” Analogical arguments, unlike any other arguments we look at in this book, have a built-in logical shortcoming.

Let’s take another look at the logical form of arguments from analogy:

• A (basic analog) is F (basic similarity) and G (inferred similarity).
• B (inferred analog) is F (basic similarity).
• ∴ B (inferred analog) is G (inferred similarity).

What is the source of logical strength for such an argument? Not the correct form condition; as with every other inductive argument, satisfying this condition merely qualifies the argument for any strength that might be conferred by the total evidence condition. Not the second part of the total evidence condition; the absence of relevant dissimilarities simply means there is no evidence to undermine whatever strength it has. [2]  This leaves the first part of the total evidence condition as the sole positive source of logical strength.

How does the first part of the total evidence condition provide logical strength? By virtue of the fact that the basic similarity counts in favor of the inferred similarity. But what does count in favor of mean here? The only meaning I know is a sound argument can be offered for it. So we can now see that logically strong analogical arguments derive their logical strength from another argument—the argument that can be offered from the inferred similarity to the basic similarity. We will call such an argument (an argument from F to G —see premise 1 of the form clarified above) a background argument . Stated simply: an analogical argument’s only logical strength is borrowed from a background argument.

Any other sort of argument can, in principle, lend its strength to an argument from analogy. For example, in the preceding chapter we looked briefly at the argument Every Japanese car I’ve ever owned has been well built, so that Toyota is probably well built. It could easily be clarified as an argument from analogy, clarified as follows:

• Every Japanese car I’ve ever owned has been a Japanese car and has been well built.
• [That Toyota is a Japanese car.]
• ∴ That Toyota is well built.

If the similarity is relevant in this case, it is because the background argument is a logically strong inductive generalization that goes from my experience of Japanese cars (the basic similarity) to the conclusion that Japanese cars in general are well built (the inferred similarity). The argument from analogy is logical only if this generalization works. So it borrows its logical strength from an inductive generalization.

The next passage, from Science News, provides a second example of borrowed logic in an argument from analogy.

The concept of “vintage year” took on a new meaning this week when two scientists presented the first chemical evidence that wine existed as far back as about 3500 bc. They had noticed a red stain while piecing together jars excavated from an Iranian site. They compared the stain with a similar stain in an ancient Egyptian vessel known to have contained wine. The researchers scraped the reddish residue from the jars and analyzed the samples with infrared spectroscopy. Residues from the Iranian and Egyptian jars looked alike and were full of tartaric acid, a chemical naturally abundant only in grapes. “Those crystals are a signature for wine,” says one researcher.

The argument can be clarified thus:

• The Egyptian jar had a certain red stain and contained wine.
• The Iranian jar had the same red stain.
• ∴ That Iranian jar contained wine.

In this case, if the similarity is relevant it is because the background argument is a sound explanatory argument (of a sort we will cover thoroughly in the next chapter) that establishes that the red stains (the basic similarity) have properties that are best explained as caused by wine (the inferred similarity). This argument’s logical strength is borrowed from an explanatory argument.

As a final example, arguments from analogy can even borrow their logical strength from deductive arguments. Consider the validity counterexamples of Chapter 10. In that chapter we started with an inverted—and invalid—Socrates argument:

• All men are mortal.
• Socrates is mortal.
• ∴ Socrates is a man.

We then offered as a validity counterexample this obviously invalid (because of true premises and false conclusion) Atlantic argument:

• All ponds are bodies of water.
• The Atlantic Ocean is a body of water.
• ∴ The Atlantic Ocean is a pond.

In this way we saw that the Socrates argument was invalid. Like any validity counterexample, the reasoning can be represented as an argument from analogy, clarified as follows:

• The Atlantic argument has a certain form and is invalid.
• The Socrates argument has the same form.
• ∴ The Socrates argument is invalid.

Here the relevance of the similarity depends on a deductive background argument; for the way to argue that a certain form (the basic similarity) is invalid (the inferred similarity) is by use of this valid affirming the antecedent argument, which has a self-evidently true first premise:

• If the form of an argument is such that it is possible for the premises to be true and the conclusion false, then the argument is invalid.
• This particular form is such that it is possible for the premises to be true and the conclusion false.
• ∴ The argument is invalid.

In this case, the logical strength of the analogical argument is borrowed from a sound deduction.

By its very nature, then, when an analogical argument works it works on borrowed logic. The two analogs mainly serve to get in the way by providing a basis for relevant dissimilarities. It is the background argument, which ignores the analogs and is concerned solely with the basic and inferred similarities, that serves as the argument’s motor. In the end, the background argument cannot itself be some other argument from analogy, since the background argument would depend on a background argument (and so on).

There are two practical lessons here. First, if you can see what the background argument is, bring it to the foreground when you clarify the argument, abandoning the analogical form. The Toyota argument, for example, would be much easier to evaluate properly if clarified as a complex argument composed of an inductive generalization and a frequency argument (as illustrated in Chapter 14); and the Iranian jar argument, likewise, if paraphrased as an explanatory argument. Second, if you cannot see what the background argument is, you should normally resist the temptation to judge it as logically strong until you better understand the background argument. As noted at the beginning of the chapter, analogical arguments are custom-made for the way our minds work, which makes them extraordinarily persuasive. But their inherent reliance on logical borrowing also makes them very good at concealing logical defects. When a persuasive car salesman won’t let you open the hood to inspect the motor, it may be prudent to shop elsewhere.

15.4.2 Arguments from Analogy as Psychological Lenders

From a logical point of view, analogical arguments are borrowers. But from a psychological point of view, they often put other arguments deeply into their debt. They can hint as well as hide.

Look, for example, at the Iranian jar argument. The analogy between the two stains is what suggested to the researchers that the jar had once contained wine. This set in motion a research effort in which samples scraped from both jars were examined by infrared spectroscopy, revealing crystals that were “a signature for wine.” One could perhaps say that this new evidence converts the initial analogical argument from a merely suggestive one into a logically strong one, by showing just how relevant the basic similarity (same red stain) is to the inferred similarity (that it contained wine). But it would be much clearer to simply say that the background argument displaces the argument from analogy. Analogical reasoning has lent a powerful psychological boost to the research program by producing the suggestive idea. Still, any logical strength it gains from that research program is borrowed from the background argument—that is, from the explanatory argument about crystals developed by the researchers. Clarity is increased if the initial analogy drops out of any account of the logical support for the conclusion—as long as it remains as a central feature of the history of the discovery. [3]

Analogical arguments can lend a valuable psychological boost to inquiry of every sort. Consider the free speech argument. Even if you are not persuaded by the proposed analogy between shouting fire and distributing leaflets, it is certainly suggestive. In particular, it suggests that you are wrong if you think that all expressions are protected. Further, it suggests a way of reasoning about which ones are not protected—namely, by thinking about the possible dangers caused by the speech in question. If that way of reasoning succeeds, the argument from analogy gets psychological credit for suggesting it, even if it gets no logical credit for supporting it.

Nineteenth-century philosopher John Stuart Mill aptly declared that good reasoners will consider any analogical argument as a “guidepost, pointing out the direction in which more rigorous investigations should be prosecuted.” Arguments from analogy brilliantly serve a necessary function in reasoning. We would be lost without good guideposts. But we should not confuse them with destinations.

EXERCISES Chapter 15, set (d)

Fully clarify and evaluate each of the arguments from analogy. In cases where you can see the background argument, you may clarify and evaluate either the analogical argument or the background argument.

• I’ve only seen one Hitchcock movie— Psycho. It was scary. Let’s try The Birds. I bet it will be scary too.
• To solve our drug problems, instead of outlawing drugs we must make them as safe and risk-free and—yes—as healthy as possible. It’s like sex. We recognize that people will continue to have sex for nonreproductive reasons, whatever the laws, and with that in mind we try to make sexual practices as safe as possible in order to minimize the spread of the sexually transmitted diseases.
• Question (investigator, to a university president): “Your administration will undertake reviews or investigations of members of your faculty without their being informed of the fact?”

A:  “I believe it’s very possible. I believe it happened in this case.”

Q:  “Do you consider that proper and appropriate?”

A:  “Personal opinion? Yes.”

Q: “Can you tell me why?”

A:  “I don’t know. Why not? I guess in an analogy, I don’t think J. Edgar Hoover, for example, ever advised everybody he was investigating that they were being investigated.”

Q:  “But he, J. Edgar Hoover, wasn’t running a university.”— Lingua Franca

• Breceda and lifeguards up and down the beach stressed the dangers of sleeping on the beach at night. “The people who get hurt are pretty much innocent,” Breceda said. “They take a walk on the beach at Puerto Vallarta at 3 a.m. and nothing happens, and so they assume it’s OK to do it here. But a whole different situation occurs here.” In addition to the dangers posed by muggers and rapists, people sleeping on the beach also could get run over by sweepers. — Los Angeles Times (Consider the argument attributed to the people who sleep on the beach.)
• “ Question: Surely society has a right to rid itself of a man like Ted Bundy? Answer : My main opposition to the death penalty is what it does to society. Our society kills people in cages. It is like going hunting in a zoo. In the cage they are not dangerous, but executing them is very dangerous—for us.” —I. Gray and M. Stanley, eds., A Punishment in Search of a Crime: Americans Speak Out Against the Death Penalty
• “At their August 1945 Potsdam meeting, Truman remarked to an aide, ‘Stalin is as near like Tom Pendergast as any man I know.’ Pendergast was a Missouri machine boss who helped get Truman elected to the Senate. For some superficial reason Truman concluded that, like Pendergast, Stalin was a man one could deal with, a man of his word. ‘It led Truman to believe that Stalin would hold free elections in Eastern Europe,’ says Deborah Larson, a UCLA political scientist.” — Associated Press
• Gerry Spence is serving as the pro bono defense attorney for an “environmental terrorist” who embedded metal plates in trees so that the bulldozers would be wrecked (and, potentially, the drivers injured). He is asked if “monkeywrenching” trees is ever justified. Spence’s sleight-of-hand answer reveals why he wins so many cases: “In most circumstances, breaking the law is improper. Now, suppose a tractor is about to run over a child. Is it improper to demolish the tractor? Suppose the tractor was going to run over something inanimate, a painting by Van Gogh that cost $32 million. Now, what about a tractor running down a tree? A 400-year-old original growth tree?” — Forbes
• “Thoughtful and right-minded men place their homage and consideration for woman upon an instinctive consciousness that her unmasculine qualities, whether called weaknesses, frailties, or what we will, are the sources of her characteristic and a special strength within the area of her legitimate endeavor. In actual war, it is the men who go to battle, enduring hardship and privation and suffering disease and death for the cause they follow. It is the mothers, wives, and maids betrothed, who neither following the camp nor fighting in battle, constitute at home an army of woman’s constancy and love whose yearning hearts make men brave and patriotic. So, in political warfare, it is perfectly fitting that actual strife and battle would be apportioned to men, and that the influence of woman, radiating from the homes of our land, should inspire to lofty aims and purposes those who struggle for the right.” —Grover Cleveland, Ladies Home Journal, 1905
• One philosopher, arguing that the rights of a rape victim to make decisions about her body can be more important than the right to life of a fetus, develops the following analogy: “Let me ask you to imagine this. You wake up in the morning and find yourself back to back in bed with an unconscious violinist. A famous unconscious violinist. He has been found to have a fatal kidney ailment, and the Society of Music Lovers has canvassed all the available medical records and found that you alone have the right blood type to help. They have therefore kidnapped you, and last night the violinist’s circulatory system was plugged into yours, so that your kidneys can be used to extract poisons from his blood as well as your own. The director of the hospital now tells you, ‘Look, we’re sorry the Society of Music Lovers did this to you—we would never have permitted it if we had known. But still, they did it, and the violinist now is plugged into you. To unplug you would be to kill him. But never mind, it’s only for nine months. By then he will have recovered from his ailment, and can safely be unplugged from you.’ Is it morally incumbent on you to accede to this situation?” —Judith Jarvis Thompson, Philosophy and Public Affairs
• “Look round the world. Contemplate the whole and every part of it. You will find it to be like one great machine, subdivided into an infinite number of lesser machines, which again admit of subdivisions to a degree beyond what human senses and faculties can trace and explain. All these various machines and their parts are adjusted to each other with an accuracy which ravishes into admiration all men who have ever contemplated them. From this we can see that the curious adapting of means to ends throughout all nature resembles exactly, though it much exceeds, the adapting of means to ends in the things made by human beings. Since, therefore, the effects resemble each other, we are led to infer, by all the rules of analogy, that the causes also resemble, and that there is an Author of Nature who is somewhat similar to the mind of man, though possessed of much larger faculties, proportioned to the grandeur of the work which he has executed. Therefore we prove at once the existence of God and his similarity to human mind and intelligence.” —David Hume, Dialogues Concerning Natural Religion

15.5 Summary of Chapter Fifteen

Arguments from analogy typically contend that because two items are the same in one respect, they are the same in another respect. The basic analog is compared to the inferred analog; because they have the basic similarity in common, it is concluded that the inferred analog also has the inferred similarity.

The total evidence condition has two parts. First, the basic similarity must be relevant—that is, it must count toward the presence of the inferred similarity. Second, there must not be any dissimilarities that are relevant—that is, any dissimilarity between the two analogs must not make the basic analog a better candidate for the inferred property. The argument is logically weaker to the extent that it fails in either of these two areas.

Their only positive logical strength comes from the background argument that establishes that the inferred similarity follows from the basic similarity; thus, whatever logical success analogical arguments have is borrowed. This makes it especially important to pay close attention to the first part of the total evidence condition. On the other hand, analogical arguments play an important psychological role in suggesting lines of reasoning, and so should be cultivated for that purpose.

15.6 Guidelines for Chapter Fifteen

• Structure arguments from analogy, when it would be loyal to do so, by identifying four things—the basic and inferred analogs and the basic and inferred similarities—then inserting each into its proper place in the form. Remember that the second premise, which declares the basic similarity, is often implicit.
• In considering whether an argument from analogy has satisfied the total evidence condition, first ask, Is the basic similarity relevant? To answer this question, look at the extent to which the basic similarity counts in favor of the inferred similarity.
• When the basic similarity is described by a general term, consider whether its meaning shifts from one use to the next. If it shifts enough to affect the soundness of the argument, revise your clarification to eliminate the ambiguity.
• In considering whether an argument from analogy has satisfied the total evidence condition, ask next, Are any of the dissimilarities relevant? To answer this question, look at the extent to which any dissimilarity makes the basic analog a better candidate than the inferred analog for the inferred property.
• When you can clearly see the background argument, clarify it rather than the argument from analogy. When you cannot see the background argument, you should normally reserve final judgment about the strength of the argument’s logic.

15.7 Glossary for Chapter Fifteen

Analogs —the two things (or classes of things) that are said to be similar in an argument from analogy.

Argument from analogy —an argument that asserts that because two items are the same in one respect, they are the same in another respect. They can be represented by this form:

Background argument —an argument that shows that the inferred similarity (of an analogical argument) follows from the basic similarity—that is, an argument that shows that the basic similarity is relevant.

Basic analog —in an argument from analogy, the item that we are presumably more familiar with, which is presumably known to have both the basic and the inferred similarities.

Basic similarity —in an argument from analogy, the property that the two analogs share, presumably without controversy.

Fallacy of false analogy —the mistake of using an argument from analogy in which the basic similarity is not relevant or in which there are relevant dissimilarities between the basic and inferred analogs. Because this term says nothing about what precisely has gone wrong with the argument, it is better to explain more specifically how it is that some necessary condition for soundness has not been satisfied. Also called the fallacy of faulty analogy.

Inferred analog —in an argument from analogy, the item in question, about which the argument is drawing its conclusion.

Inferred similarity —in an argument from analogy, the property that the inferred analog is alleged to have because the basic analog has it.

• The British usually spell it analogue . Historically, the term was analogon . ↵
• The second part of the total evidence condition for frequency arguments operates the same way. ↵
• To use terminology mentioned elsewhere in the text, it is important in the context of discovery, but not in the context of justification. ↵

An argument that asserts that because two items are the same in one respect, they are the same in another respect. They can be represented by this form:

1. A is F and G. 2. B is F. ∴ C . B is G.

The two things (or classes of things) that are said to be similar in an argument from analogy.

In an argument from analogy, the item that we are presumably more familiar with, which is presumably known to have both the basic and the inferred similarities.

In an argument from analogy, the item in question, about which the argument is drawing its conclusion.

In an argument from analogy, the property that the two analogs share, presumably without controversy.

In an argument from analogy, the property that the inferred analog is alleged to have because the basic analog has it.

The mistake of using an argument from analogy in which the basic similarity is not relevant or in which there are relevant dissimilarities between the basic and inferred analogs. Because this term says nothing about what precisely has gone wrong with the argument, it is better to explain more specifically how it is that some necessary condition for soundness has not been satisfied. Also called the fallacy of faulty analogy.

An argument that shows that the inferred similarity (of an analogical argument) follows from the basic similarity—that is, an argument that shows that the basic similarity is relevant.

A Guide to Good Reasoning: Cultivating Intellectual Virtues Copyright © 2020 by David Carl Wilson is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License , except where otherwise noted.

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What Is Analogy? Definition, Usage, and Literary Examples

Analogy definition.

An  analogy  (uh-NAHL-uh-gee) is a rhetorical device in which a writer compares the shared qualities of two unrelated objects. They are different from  similes  and  metaphors , which also compare unrelated objects by equating them. However, an analogy can employ either one to drive home its larger point. Analogies support logic, present rational arguments, and back up ideas by showing the relationship between disparate things.

The word  analogy  comes from the Greek  analogia , meaning “proportion,” which builds off  ana , meaning “according to,” and  logos , meaning “ratio.”

How to Construct an Analogy

Most analogies in literature,  rhetoric , and everyday communication contain two components: the unknown concept, which is the target, and the known concept, which is the source. The target is the idea the analogy hopes to explain, while the source is the idea used to explain it. The source is something familiar or widely understood to most people; the target is something unfamiliar and mysterious.

When creating a link between the two concepts, writers are essentially making the unfamiliar into something familiar. For example, take the classic line from  Forrest Gump : “Life is like a box of chocolates. You never known what you’re gonna get.” Forrest, quoting his mother in this line, uses a box of assorted chocolates as the source, comparing it to a target that is nebulous and difficult to understand: life. Connecting the two concepts illuminates a specific insight about the randomness of life.

In logic and reasoning, and occasionally in literature, analogies are a four-part comparison expressed via the formula of A:B::C:D, or A is to B as C is to D. This comparison depends on the relationship between A and B and the relationship between C and D to make its point, so A can never be D, and B can never be C. For instance, in the analogy “Haggis is to Scotland as caviar is to Russia,” haggis (A) is a food associated with Scotland (B), just as caviar (C) is a food associated with Russia (D). It explains that haggis originated in Scotland by equating its relationship to the relationship between caviar and Russia, as the former originated in the latter.

Relationships that Analogies Can Convey

There are several different comparative concepts that can fit into the A:B::C:D formula.

• Opposite relationships, or antonyms: “cold is to hot as night is to day”
• Similar relationships, or synonyms: “draw is to sketch as sofa is to couch”
• Cause and effect relationships: “smiles are to joy as tears are to grief”
• Part-to-whole relationships: “finger is to hand as leaf is to tree”
• Location relationships: “apples are to orchards as fish are to sea”
• Object-to-action relationships, wherein objects are paired with associated actions: “bake is to pie as simmer is to soup”
• Performer-to-action relationships: “actor is to acting as writer is to writing”
• Performer-to-object relationships: “plumber is to wrench as artist is to paintbrush”
• Function relationships: “pencil is to writing as knife is to cutting”
• Attribute or characteristic relationships: “teachers emit wisdom as lamps emit light”
• Classification relationships: “ waltz is to dance as American Beauty is to rose”

The Function of Analogies

An analogy helps make an abstract concept more tangible and relatable. Many professionals rely on sharing information, and analogies play an important role in making that information understandable. Writers, teachers, advertising and marketing professionals, government officials, scientists, and healthcare providers are just a few of the occupations that involve disseminating information to the general public. Employing analogies is a common method of ensuring an audience understands what they hear.

Analogies also inject substance and emotion into an idea or image. Writers mainly utilize this function to convey meaning and beauty in the stories they tell. It’s nearly impossible to read a novel or a  poem  without finding at least one analogy.

Finally, analogies make compelling arguments in rhetoric. Advertising and marketing lingo, political debates, and  didactic  nonfiction works are some of the arenas where analogies present powerful, persuasive arguments. In 2009, President Barack Obama responded to the Republican criticism of his proposals with a potent analogy comparing politicians’ responsibilities with mopping up messes. “I’m busy. Nancy’s busy with our mops cleaning up somebody else’s mess,” he said. “We don’t want somebody sitting back saying ‘You’re not holding the mop the right way.’ Why don’t you grab a mop? Why don’t you help clean up? ‘You’re not mopping fast enough! That’s a socialist mop!’ Grab a mop. Let’s get to work.”

Analogies, Similes, and Metaphors

While these terms all involve making comparisons, they differ in that analogies merely point out commonalities between two unrelated things, while  similes  and  metaphors  are  figures of speech  that imply the unrelated things are equals. Both similes and metaphors are popular in the target/source approach to analogies.

The difference between similes and analogies is subtle. A simile compares two things through the words  like  or  as . While it can have a powerful effect when making comparisons, analogies address more detailed explanations that elevate the relationship between the compared concepts. The earlier  Forrest Gump  quote is an example of both a simile and an analogy. The first part of the movie line—“Life is like a box of chocolates”—is a simile. The subsequent explanation—“You never know what you’re gonna get”—expands upon the simile’s concept to make a larger point; thus, it is an analogy.

Metaphors and analogies have a similar relationship. Metaphors compare two objects directly, without the linking words that similes use. For example, here is a famous excerpt from the  William Shakespeare  classic  Romeo and Juliet , spoken by Juliet:

What’s in a name? That which we call a rose

By any other word would smell as sweet.

So Romeo would, were he not Romeo call’d,

Retain that dear perfection which he owes

Without that title.

In this passage, Juliet compares Romeo’s perceived perfection to a rose’s sweet scent; since she does not use linking words to state this similarity, her description is a metaphor. It becomes an analogy because she expounds upon it. She starts by declaring that names are irrelevant. To prove this point, she posits that a rose will always smell like a rose no matter what one might call it. Bringing the analogy to a close, she says that, just like the rose, Romeo will remain who he is—someone she loves—no matter what name he has.

Examples of Analogies in Literature

1. William Shakespeare,   As You Like It

Shakespeare’s comedy involves a woman named Rosalind escaping persecution at her uncle’s court and fleeing to the Forest of Arden. There, she finds a cast of quirky characters, including an introspective traveler named Jacques. He delivers one of Shakespeare’s most memorable monologues:

All the world’s a stage,

And all the men and women merely players;

They have their exits and their entrances,

And one man in his time plays many parts,

His acts being seven ages. At first, the infant,

Mewling and puking in the nurse’s arms.

Then the whining schoolboy, with his satchel

And shining morning face, creeping like snail

Unwillingly to school. And then the lover,

Sighing like furnace, with a woeful ballad

Made to his mistress’ eyebrow. Then a soldier,

Full of strange oaths and bearded like the pard,

Jealous in honor, sudden and quick in quarrel…

In this passage, Jacques likens the world to a stage and all the world’s inhabitants to actors performing on the stage. By saying “one man in his time plays many parts,” Jacques—and Shakespeare through him—implies that the roles people fulfill evolve throughout the natural span of human life. Even further, he compares this evolution to the “acts” that make up a play.

2. T.S. Eliot, “The Love Song of J. Alfred Prufrock”

Eliot’s  narrative poem  encompasses a series of thoughts by a narrator on the search for love in a loveless world. Despite the title, it is less a love song and more of a collection of fragmented ideas about frustrated and unexpressed love and devotion.

Let us go then, you and I,

When the evening is spread out against the sky

Like a patient etherized upon a table;

Let us go, through certain half-deserted streets,

The muttering retreats

Of restless nights in one-night cheap hotels

And sawdust restaurants with oyster-shells:

Streets that follow like a tedious argument

Of insidious intent

To lead you to an overwhelming question …

Oh, do not ask, “What is it?”

Let us go and make our visit.

This excerpt depends on vivid analogies. The narrator paints a scene of emptiness and despair by comparing a night to an unconscious patient on an operating table—something that is inert and seemingly lifeless. He also equates the meandering streets to monotonous and devious disputes—both taking travelers places they may not want to go. The result is a bleak snapshot of a city at night and the hopeless man at the center of it.

3. Milan Kundera,   The Unbearable Lightness of Being

Kundera’s novel follows the overlapping stories of Tomáš, Tereza, Sabina, and Franz during the 1968 Prague Spring in Czechoslovakia. Kundera presents many analogies throughout the course of the story. The following passages discuss the depth of Tomáš’s sudden, shockingly intense feelings for Tereza:

He kept recalling her lying on his bed; she reminded him of no one in his former life. She was neither mistress nor wife. She was a child whom he had taken from a bulrush basket that had been daubed with pitch and sent to the riverbank of his bed. She fell asleep. He knelt down next to her….

He had come to feel an inexplicable love for this all but complete stranger; she seemed a child to him, a child someone had put in a bulrush basket daubed with pitch and sent downstream for Tomáš to fetch at the riverbank of his bed.

Kundera underscores Tereza’s innocence and her need to be cared for by comparing her to a helpless child in “a bulrush basket that had been daubed with pitch and sent to the riverbank of his bed.” This analogy employs a metaphor to equate Tereza to the Biblical Moses, who, as a baby, was saved from a basket floating down a river.

Further Resources on Analogies

John F. Sowa and Arun K. Majumdar delve into the details of  using analogies in logical reasoning .

Butte College offers some guidance on  how to write an analogy .

iWriteEssays shares tips on  writing an analogy in essay form .

Copyblogger talks about  the power of analogies in business and marketing .

An academic paper by Yan Chang explores  rhetorical functions and structural patterns of analogies .

Related Terms

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Course: LSAT   >   Unit 1

• Getting started with Reading Comprehension
• Catalog of question types | Reading comprehension
• Main point | Quick guide
• Recognition | Quick guide
• Clarifying meaning | Quick guide
• Purpose of reference | Quick guide
• Organizing information | Quick guide
• Inferences about views | Quick guide
• Inferences about information | Quick guide
• Inferences about attitudes | Quick guide
• Applying to new contexts | Quick guide

Principles and analogies | Quick guide

• Additional evidence | Quick guide
• Primary purpose | Quick guide

Which choice is analogous?

• “Which one of the following situations is most analogous to the one introduced in the second sentence of the passage?”
• “Which one of the following hypothetical situations is most analogous to the description in the passage of _____?”
• “The rationale for _____ as it is described in the passage is most consistent with which one of the following principles?”

Common wrong choice types

Comparative reading variants.

• The relationship between passage A and passage B is most analogous to the relationship between the two television programs described in which one of the following?

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Analogy — Definition and Examples

What is an analogy?

An  analogy  is a comparison made to show how two things are similar for explanation or clarification. Although the things compared are physically different, the analogy identifies how they are figuratively similar.

Think of analogies as an extension of a metaphor or simile.

People use analogies to link unfamiliar ideas with common ones, making complex or abstract ideas easier to understand.

Analogy examples

It is common to use analogies to make comparisons in the English language. The following is an example analogy comparing a warrior's sword to a writer's pen:

Just as a sword is the weapon of a warrior, a pen is the weapon of a writer.

A warrior uses his sword as a weapon, while a writer's weapon is their words written with their pen.

In the next example, the analogy is comparing a book to a rollercoaster:

That book was a rollercoaster of emotion.

The book's plot had many emotional highs and lows, making it feel like you rode the ups and downs of a rollercoaster.

Analogy examples in literature

Analogies are commonly used in literature. A famous example can be found in  Romeo and Juliet  by William Shakespeare:

What’s in a name? That which we call a rose, / by any other word would smell as sweet. / So Romeo would, were he not Romeo called.”

This analogy is saying a rose would smell the same even if it were called something different; therefore, Romeo's name does not define him.

Another example from literature is found in George Orwell's  Animal Farm:

The creatures outside looked from pig to man, and from man to pig, and from pig to man again; but already it was impossible to say which was which.

In Orwell's analogy, the pigs have become that which they fought against (man).

The House in Paris  by Elizabeth Bowen contains this analogy:

Memory is to love what the sauce’r is to cup.

Like a saucer holds a cup, a memory holds onto love.

Analogy in poetry

Types of analogies.

An analogy can be both a literary device and a rhetorical device, depending upon its use.

As a rhetorical device, word analogies are often found on standardized tests. This assesses the test taker's ability to identify various relationships.

When writing a word analogy as a rhetorical device, colons stand in for words. Analogies written in this way use pairs of words to make a logical argument. Consider the following example:

Stove is to kitchen as bed is to bedroom

Stove : kitchen :: bed : bedroom

There are a variety of types of rhetorical verbal analogies that identify different kinds of relationships:

Analogy vs. metaphor vs. simile

A metaphor is a figure of speech used to compare or suggest a similarity between two items, whereas a simile is a comparison that uses the words "like" or "as." While metaphors and similes help writers show instead of tell, an analogy provides explanation or clarification.

Consider the following example comparing thoughts to a storm:

Metaphor : His thoughts were a storm.

Simile : His thoughts were like a storm.

Analogy : His thoughts were like a storm causing chaos.

Writers can use metaphors and similes to create analogies; however, not all metaphors and similes are analogies.

Learn more about  difference between metaphors, similes, and analogies .

Analogical arguments

Analogical reasoning is any thinking that involves an analogy. It compares something new with something known. Argument by analogy is a way to inform, persuade, or explain, such as in the following examples:

The new movie is supposed to be similar to the one that came out last summer, so it too is probably dull.

Not everyone had a computer in their homes 20 years ago, but most of them do now; therefore, one can expect the same of virtual reality.

The new planet is the same distance from its star as the Earth is from the sun, meaning it could support life.

Mastering the Art of Analogies: Examples and Tips for Nonfiction Writers

by Harry Wallett

In this blog post, we’ll explore the ins and outs of using analogies to create vivid, memorable, and easy-to-understand pieces that resonate with your readers.

Picture this: you’re trying to explain a complex idea or concept to your readers, and you can see their eyes glazing over as they struggle to grasp your point. Frustrating, isn’t it? That’s where analogies come in.

By comparing your complicated idea to something more familiar and relatable, you can help your readers understand and retain the information you’re sharing.

In fact, analogies are an incredibly valuable addition to your writer’s toolbox. To help you master this technique, we’ll cover the basics of what an analogy is and how it differs from metaphors and similes.

We’ll then delve into the different types of analogies and provide examples from various nonfiction sources to show you how it’s done.

Let’s get started!

What is an analogy?

An analogy is a comparison between two things that are alike in some way, usually to explain a complex idea or concept in simpler terms.

Unlike metaphors and similes, which compare two things directly, analogies highlight the relationship between the two things being compared.

For example, you could say that writing is like cooking: both require skill, creativity, and the right ingredients (words or ideas) to create a satisfying result.

Types of Analogies

Understanding the different types of analogies can help you use them more effectively in your nonfiction writing. By recognizing the various forms that analogies can take, you’ll be better equipped to select the right type of analogy for your specific writing needs.

Here, we’ll explore the three main types of analogies commonly used in nonfiction writing:

Structural Analogies

Structural analogies focus on the similarities in the structure or organization of the two things being compared.

These analogies help to draw parallels between the arrangement or composition of different entities, making it easier for your readers to understand the underlying structure of a complex system.

For example, you might compare the hierarchy of a company to a military chain of command. In this analogy, the CEO is like a general, middle managers are like officers, and frontline employees are like enlisted soldiers.

This comparison can help your readers visualize the organizational structure of a company and understand the relationships between different levels of management.

Functional Analogies

Functional analogies highlight the similarities in how two things work or perform. These types of analogies help to explain the purpose or function of something by comparing it to another object or system with a similar function.

For instance, you could compare the human heart to a pump, as both have the primary function of moving fluid through a system. The heart pumps blood throughout the body, while a mechanical pump might move water through pipes.

By drawing this parallel, your readers can better understand the role of the heart in the circulatory system.

Conceptual Analogies

Conceptual analogies explore the similarities in the underlying concepts or ideas of the two things being compared.

These analogies can be particularly useful for explaining abstract ideas or theories by connecting them to more concrete or familiar concepts.

An example might be comparing the internet to a library, as both serve as repositories of information.

While the internet is a vast digital network that connects users to websites, articles, and other resources, a library is a physical space housing books, journals, and other sources of knowledge.

This analogy can help your readers understand the broader concept of the internet as a massive, interconnected storehouse of information.

How to Create Effective Analogies

Crafting the perfect analogy can be a bit of an art form, but with practice and a few guiding principles, you can create powerful comparisons that will elevate your nonfiction writing.

Here are some key tips to keep in mind when creating effective analogies:

Choose relatable and easily understood comparisons

The success of an analogy often hinges on its relatability. To help your readers grasp a complex concept, choose comparisons that are familiar and easily understood.

When your analogy is based on common experiences or objects, it becomes more accessible, allowing your readers to quickly make connections between the two ideas.

Consider your target audience’s background, interests, and experiences when selecting a comparison, and opt for analogies that will resonate with them.

Ensure the analogy supports your main point

An effective analogy should serve to clarify your argument or idea, not distract from it. Be sure that your chosen comparison supports your main point and enhances your readers’ understanding of the topic.

If an analogy seems to muddy the waters or lead your readers away from your central message, it’s best to rethink your approach and choose a different comparison that better aligns with your goals.

Be concise and avoid over-complicating the analogy

While it can be tempting to get lost in the details of a comparison, remember that the goal of an analogy is to simplify a complex concept for your readers. Aim to be concise and avoid over-complicating the analogy, as this can lead to confusion rather than clarification.

Focus on the most relevant and impactful similarities between the two ideas, and leave out extraneous details that might detract from your main point.

Test your analogy for effectiveness

Before committing to an analogy in your writing, it’s a good idea to test it for effectiveness. Consider running your analogy by a trusted friend, colleague, or editor, and ask for their feedback.

Does the analogy help them understand the concept better? Is it clear and concise? Their input can be invaluable in determining whether your analogy is hitting the mark or if it needs further refinement.

Don’t overuse analogies

While analogies can be powerful tools in nonfiction writing, it’s important not to overuse them. Relying too heavily on analogies can make your writing feel repetitive or overly simplistic.

Strike a balance by using analogies judiciously, reserving them for instances where they truly enhance your readers’ understanding of a complex idea or concept.

Examples of Analogies in Nonfiction Writing

Let’s take a look at some examples:

• In his book “The Tipping Point,” Malcolm Gladwell compares the spread of ideas and trends to the spread of a virus, highlighting how certain factors can cause ideas to “infect” large numbers of people quickly and seemingly without warning.
• In an article on climate change, you might use the analogy of a bathtub filling with water to explain how greenhouse gas emissions accumulate in the atmosphere, leading to global warming.
• Martin Luther King Jr., in his famous “I Have a Dream” speech, used the analogy of a “bad check” to represent the unfulfilled promises of justice and equality for African Americans in the United States.

Tips for using analogies in your writing

Here are three handy tips for incorporating analogies into your nonfiction writing:

Know your audience: Make sure your analogies are appropriate for your target readers and consider their background knowledge and experiences.

Use analogies sparingly and intentionally: While they can be powerful tools, overusing analogies can make your writing feel cluttered or forced. Use them when they genuinely enhance your message.

Revise and refine your analogies for clarity and impact: Don’t be afraid to tweak or even scrap an analogy if it’s not working as well as you’d like. Sometimes it takes a bit of trial and error to find the perfect comparison.

Benefits of using analogies in nonfiction writing

So, why should you bother incorporating analogies into your writing? There’s a multitude of reasons, and the benefits are too good to ignore.

Let’s dive into some of the key advantages of using analogies in your nonfiction work:

They enhance understanding and retention of complex concepts

Analogies are a fantastic way to break down complicated ideas into more digestible chunks. By comparing complex concepts to familiar and relatable experiences or objects, you make it easier for your readers to understand and remember your message.

This can be especially helpful when you’re tackling subjects that may be unfamiliar or difficult for your audience to grasp, like scientific or technical concepts.

They engage your reader’s imagination and emotions

By drawing on familiar experiences or images, you create vivid mental pictures that can capture your reader’s attention and make your writing more engaging and memorable.

This emotional connection can also help your readers to empathize with the subjects of your writing, fostering a deeper understanding and appreciation for your topic.

They strengthen your argument and persuade your reader

Analogies can serve as powerful rhetorical devices, helping to drive home your point and convince your reader of your perspective. When used effectively, an analogy can clarify your argument, making it more accessible and persuasive.

This is particularly useful when you’re trying to explain an abstract concept or idea, as it helps to ground your argument in more concrete terms that your readers can easily understand and relate to.

They can aid in creative problem-solving and critical thinking

Analogies can also help your readers see connections between seemingly unrelated concepts or ideas, fostering creative problem-solving and critical thinking.

By exploring similarities between different subjects, you can help your readers develop new perspectives and insights, broadening their understanding of the world around them.

This can lead to novel approaches to tackling challenges, as well as a deeper appreciation for the interconnectedness of various aspects of our lives.

They create a relatable and personable writing style

Incorporating analogies into your writing can also make your work feel more relatable and personable. This can be particularly beneficial in nonfiction writing, where the subject matter might be dry or technical.

By using analogies that resonate with your readers’ experiences or interests, you can create a more engaging and approachable tone, making your writing feel more like a conversation than a lecture.

Wrapping Things Up

Mastering the art of using analogies in your nonfiction writing can transform your work from good to great. By thoughtfully incorporating analogies, you’ll be able to break down complex concepts, engage your readers on a deeper level, and create memorable connections that will make your writing stand out in a sea of content.

But, as with any writing technique, the key to truly mastering analogies lies in practice and experimentation. Don’t be afraid to play around with different comparisons and ideas, and remember that finding the perfect analogy may take some time and effort.

Keep refining your approach, and you’ll soon discover that the power of analogies lies not only in their ability to explain and persuade but also in their capacity to reveal new insights and perspectives that can enrich both your writing and your readers’ understanding of the world.

Happy writing!

Harry Wallett is the Managing Director of Cascadia Author Services. He has a decade of experience as the Founder and Managing Director of Relay Publishing, which has sold over 3 million copies of books in all genres for its authors, and looks after a team of 50+ industry professionals working across the world.

Harry is inspired by the process of book creation and is passionate about the stories and characters behind the prose. He loves working with the writers and has shepherded 1000s of titles to publication over the years. He knows first-hand what it takes to not only create an unputdownable book, but also how to get it into the hands of the right readers for success.

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Choose Your Test

Sat / act prep online guides and tips, analogy questions in sat reading: strategies and tips.

SAT Reading

Though direct analogy questions were eliminated along with the old SAT Verbal Reasoning section in 2005, analogy questions remain in place in a more abstract form in the Critical Reading section. 

In this article, I’ll show you what analogy questions look like, the best way to approach them, and some step by step examples for solving them with real questions from the SAT!

What Is An Analogy Question?

Before we learn how to solve these types of questions, we need to learn how to spot them in the first place. 

Analogy questions will ask you to make comparisons.  They might ask you to compare a relationship between two things in the passage with a relationship between two things in the answer choices, or they might just ask for the answer choice that is most similar to something in the passage.

Here’s an example of an analogy question:

Which of the following most resembles the relationship between "black hole activity" and "star formation" (lines 11-12) as described in the passage?

A. A volcanic eruption on one continent results in higher rainfall totals on another continent. B. Industrial emissions in one region lead to an increase in airborne pollutants in adjacent regions. C. A drought in a wilderness area causes a significant loss of vegetation in that area. D. Decreased oil production in one country results in higher gas prices in oil-dependent countries. E. Overfishing in a gulf leads to an increase in the population of smaller aquatic organisms. 

In this case, you would have to examine the cause and effect relationship between black hole activity and star formation described in the passage and see which of the five choices is most similar to that relationship.

Analogy questions are a subset of inference questions because they require you to understand a relationship or condition in the passage and then take it one step further to infer the similarity of something NOT mentioned in the passage.

How Do I Solve Analogy Questions?

You’re going to have to take a couple of mental steps to solve analogy questions (which is why they can be one of the more confusing question types).

Step 1: Read the question carefully.

This is important because some analogy questions will ask you for the relationship that is LEAST like the one in the passage.  Make sure you know what you’re looking for!

Step 2: Understand the relationship or condition in the passage.

Go back and read the relevant section of the passage.  If you think it will help you to remember the nature of the relationship or condition mentioned in the question, sum it up in simpler terms.  Make sure you fully understand what specifically you’re going to be comparing to the potential answer choices. 

Step 3: Go through the answer choices, break them down, and eliminate the duds.

Look at each relationship or condition presented in the answer choices, and see if it is functionally the same as what you found in the passage. Remember that the point of an analogy question is that the concrete details are different, but the core relationship or condition is a match between the passage and the answer choice. If this is not the case, eliminate it (unless it’s a LEAST question, of course).

Keep going with this until you have only one correct answer!

Ok, that sounds doable. Let’s try a sample question.

Analogies in Action

Now for our first real sat analogy question.

Here it is:

Which most resembles the "irony" mentioned in line 34?

A. A worker moving to a distant state to take a job, only to be fired without warning B. An executive making an important decision, only to regret it later C. An athlete earning a starting position on a good team, only to quit midseason D. A student studying for a major exam, only to learn that it has been postponed E. A person purchasing an expensive umbrella, only to lose it on the first rainy day

First, let’s make sure we read the question carefully - looks like this one is pretty straightforward. No LEASTs here.  We are clearly looking for the answer choice that is most similar to a condition in the passage.

Ok, now we will refer to the passage. Here’s the sentence we need to reference:

As she wrote a final letter on her typewriter - she did hate letting the old machine go - Georgia did considerable philosophizing about the irony of working for things only to the end of giving them up.

What is the irony mentioned in the passage? Looks like it's “working for things only to the end of giving them up.” So: we are going to be looking for an answer that demonstrates working hard for something but later deciding to abandon it.

Now we can go through the answer choices to find our winner! For these answer choices, I thought it was helpful to break them down into two parts to show exactly why each incorrect choice was eliminated.

Choice A: A worker moving to a distant state to take a job, only to be fired without warning

A worker moving to a distant state to take a job - Ok, the first part of this answer sounds promising. That's definitely an example of someone putting in effort for something. Now let's look at the second part.

Only to be fired without warning - No, that’s not going to fit. Being fired doesn’t mean you gave up, it means someone else gave up on you.

This doesn’t match the irony described in the passage, so let's eliminate it!

Choice B: An executive making an important decision, only to regret it later

An executive making an important decision - Eh, that doesn’t really fit with working towards something.

Only to regret it later - Regret isn't the same as giving up, so this part doesn't work either.

This doesn’t match the irony described in the passage either - get rid of it!

Choice C: An athlete earning a starting position on a good team, only to quit in midseason

An athlete earning a starting position on a good team - Ok, that’s definitely working towards something.

Only to quit in midseason - Yes, that’s absolutely giving up.

Looks like it matches the irony described in the passage.  This choice works!

Choice D: A student studying for a major exam, only to learn that it has been postponed

A student studying for a major exam - Yes, this part makes sense as working towards something.

Only to learn that it has been postponed - No, this isn't the same as giving up because something happened that was outside of the student’s control.

It doesn’t match the irony described in the passage, so cross it out!

Choice E: A person purchasing an expensive umbrella, only to lose it on the first rainy day

A person purchasing an expensive umbrella - Nope, that's not really an example of working towards a goal unless your priorities are seriously weird.

Only to lose it on the first rainy day - That’s not giving up , this person is just frivolous AND careless. I’m glad they lost their umbrella.

This doesn’t match the irony described in the passage either - eliminate it!

Great, so we have Choice C as our answer!

"O Umbrella, why did you leave me? O cruel vagaries of fate!" - quote from the poor sap in choice E

Let's try another one.

The first sample analogy question that I showed you about black holes is pretty tough, but I think we're ready for it. Here it is again:

Ok, first we need to read the question carefully. We are going to be comparing two relationships for this question, and there's no LEAST, so we want to find the answer choice that is most similar to the relationship in the passage. 

Now let's read the lines from the passage. Here's our relevant excerpt:

Accordingly, astronomers long assumed that supermassive holes, let alone their smaller cousins, would have little effect beyond their immediate neighborhoods. So it has come as a surprise over the past decade that black hole activity is closely intertwined with star formation occurring farther out in the galaxy.

What's the relationship between black hole activity and star formation? They are "closely intertwined," implying a cause-effect relationship of some kind, although the star formation is occurring very far away from the black hole activity. So we are looking for a vague cause and effect relationship between two events that are occurring far apart from one another. 

Now let's examine our answer choices to see which one matches up with this relationship. 

Choice A: A volcanic eruption on one continent results in higher rainfall totals on another continent.

This answer seems to work. The volcanic eruption and the higher rainfall totals are occurring in two separate regions , just like the black hole activity and star formation.

This answer also demonstrates a cause and effect relationship that is somewhat ambiguous - though the events are related, they do not directly lead into one another. The nature of this relationship is the same as that of the relationship between black hole activity and star formation. 

Choice B:   Industrial emissions in one region lead to an increase in airborne pollutants in adjacent regions.

The key to detecting this wrong answer is the word "adjacent" . Black hole activity and star formation in the passage are occurring very far away from each other, not in nearby regions of the galaxy.

This answer also describes a direct causal relationship that makes straightforward logical sense - that's different from the vague nature of the relationship in the passage. Get rid of this one!

Choice C:  A drought in a wilderness area causes a significant loss of vegetation in that area.

This answer is incorrect because both events are occurring in the same area. This makes it even more clearly wrong than Choice B, where the events happened in adjacent regions.

This answer also describes a very logical relationship that demonstrates obvious cause and effect between drought and loss of vegetation. This is not the same as the relationship between black hole activity and star formation. Eliminate this one too!

Choice D:  Decreased oil production in one country results in higher gas prices in oil-dependent countries.

Though the two events in this relationship are occurring in regions that are far away from one another, this answer still doesn't work. This relationship demonstrates a direct and logical cause and effect chain of events. This was not the case with black hole activity and star formation. Cross it out!

Choice E:  Overfishing in a gulf leads to an increase in the population of smaller aquatic organisms. 

This once again refers to a scenario where both events are occurring in the same place , whereas a key feature of the relationship in the passage was that black hole activity and star formation happened far away from each other. This one's wrong too!

Looks like Choice A is our answer!

That was a really tough one, but if you understood why we eliminated the four incorrect answers, you shouldn't have to worry about any super challenging analogy questions sneaking up on you on the SAT. You've already got the skills to beat them.

Analogy questions (in a less direct form) are still a part of the SAT Critical Reading section. These questions will ask you to make a comparison between a condition or relationship in a reading passage and a different condition or relationship that’s not referenced in the passage.

When you see an analogy question, remember to:

Read the question carefully.

Go back to the passage and make sure you fully understand the condition or relationship you are being asked to compare.

Read each of the answer choices and break them down so that you can make a direct comparison to what’s in the passage.

Eliminate four choices , and find the one that works!

Remember, you can do it!

What's Next?

Want more skills-focused SAT Reading articles? Start with these articles on sentence completion questions and vocab-in-context questions , and check back in the next week for more!

What's the best way to get information out of a passage on SAT Reading? Find out the best way to read the passage and what's actually on SAT Reading .

Worried that vocab is going to trip you up? Don't worry - we can help .

Want to improve your SAT score by 160 points? 

Check out our best-in-class online SAT prep program . We guarantee your money back if you don't improve your SAT score by 160 points or more.

Our program is entirely online, and it customizes what you study to your strengths and weaknesses . If you liked this Reading lesson, you'll love our program.  Along with more detailed lessons, you'll get thousands of practice problems organized by individual skills so you learn most effectively. We'll also give you a step-by-step program to follow so you'll never be confused about what to study next.

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Samantha is a blog content writer for PrepScholar. Her goal is to help students adopt a less stressful view of standardized testing and other academic challenges through her articles. Samantha is also passionate about art and graduated with honors from Dartmouth College as a Studio Art major in 2014. In high school, she earned a 2400 on the SAT, 5's on all seven of her AP tests, and was named a National Merit Scholar.

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How to Do Analogies

Last Updated: August 10, 2021 References

This article was co-authored by Christopher Taylor, PhD . Christopher Taylor is an Adjunct Assistant Professor of English at Austin Community College in Texas. He received his PhD in English Literature and Medieval Studies from the University of Texas at Austin in 2014. There are 8 references cited in this article, which can be found at the bottom of the page. This article has been viewed 20,459 times.

Analogies are an important part of writing and test-taking in many schools, but they can be a challenge to master. When writing, analogies make comparisons between two concepts so that your reader can better understand something unfamiliar. On tests, questions called verbal analogies test your reasoning by asking you to properly complete comparisons. It might take some practice to understand analogies, but when you learn the concept and work on it a little every day, you can master them.

Solving Verbal Analogies on Tests

• Uses, such as cup is to drink.
• Users, such as contractor is to hammer.
• Places, such as Santiago is to Chile.
• Product to producer, such as wool is to sheep.
• Degree of intensity, such as warm is to scalding.

• If you have an analogy saying, “water : glass : : cereal : _____,” then you need to think about how the water and glass relate to each other. Water goes in a glass, so the proper choice for the cereal would be “bowl” as opposed to choices like “plate” or “spoon.”

• If you have 30 minutes to complete 50 analogies, for example, you could allow 30 seconds for each question. This gives you time to consider each question, as well as a buffer to go back and answer questions you skipped earlier.

Using Analogies in Your Writing

• “Her smile was a ray of sunshine,” would be a metaphor. “Her smile was as bright as a beam of sun,” would be a simile. An analogy would make more particular comparisons between a smile and the sun. “The warmth and intensity of her smile was as bright as a beam of light,” makes multiple, direct connections between the smile and light.
• “That meeting was a rollercoaster,” is a metaphor. “That meeting was like a rollercoaster,” is a simile. “That meeting was a rollercoaster ride of emotions,” is an example of an analogy.

• Comparing the color of a blue shirt to the color of the sky, for example, would best be done with a simile or metaphor. Comparing the movement of electricity through wires to the flow of water through pipes, however, should be done with an analogy.

• When describing an okapi, for example, it is easiest to say, "This animal looks like a short-necked giraffe with zebra striping on its legs and brown fur on its body." This draws on what your reader already knows about zebras and giraffes to help them visualize the animal.

• With the water and electricity example, the comparison would be that electricity flows through wires like water through pipes. You do not need to explain how electric currents are generated to get your point across. [6] X Research source

Working on Analogies at Home

• Make sure to take a practice test similar to the test you will take. An ACT prep test won’t help you much if you are getting ready for the GRE.
• There are a number of practice tests available for free online for a broad range of tests. Take a few tests from a few sources to get more practice.

• What if feels like getting out of bed.
• How you feel taking a difficult test.
• What it’s like to finish a good book.
• How you go about trying to make new friends.
• How to make a peanut butter and jelly sandwich.

Expert Q&A

You might also like.

• ↑ http://www.mhhe.com/socscience/english/spears/stu3/studisk/verbal_analogies/va_intro.htm
• ↑ http://www.vocabulary.co.il/analogy_relationships/
• ↑ https://www.kaptest.com/blog/med-school-pulse/2016/07/06/mastering-test-day-time-management/
• ↑ http://www.copyblogger.com/metaphor-simile-and-analogy-whats-the-difference/
• ↑ http://examples.yourdictionary.com/analogy-ex.html
• ↑ https://www.teachervision.com/professional-development/metaphors-analogies
• ↑ https://www.kaptest.com/blog/grad-school-insider/2017/06/21/manne-plan-take-free-gre-practice-test/
• ↑ https://goinswriter.com/get-a-peer-editor/

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