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1.1: What is Philosophy?

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Nathan Smith et al.

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Learning Objectives

By the end of this section, you will be able to:

Identify sages (early philosophers) across historical traditions.
Explain the connection between ancient philosophy and the origin of the sciences.
Describe philosophy as a discipline that makes coherent sense of a whole.
Summarize the broad and diverse origins of philosophy.

It is difficult to define philosophy. In fact, to do so is itself a philosophical activity, since philosophers are attempting to gain the broadest and most fundamental conception of the world as it exists. The world includes nature, consciousness, morality, beauty, and social organizations. So the content available for philosophy is both broad and deep. Because of its very nature, philosophy considers a range of subjects, and philosophers cannot automatically rule anything out. Whereas other disciplines allow for basic assumptions, philosophers cannot be bound by such assumptions. This open-endedness makes philosophy a somewhat awkward and confusing subject for students. There are no easy answers to the questions of what philosophy studies or how one does philosophy. Nevertheless, in this chapter, we can make some progress on these questions by (1) looking at past examples of philosophers, (2) considering one compelling definition of philosophy, and (3) looking at the way academic philosophers today actually practice philosophy.

Historical Origins of Philosophy

One way to begin to understand philosophy is to look at its history. The historical origins of philosophical thinking and exploration vary around the globe. The word philosophy derives from ancient Greek, in which the philosopher is a lover or pursuer ( philia ) of wisdom ( sophia ). But the earliest Greek philosophers were not known as philosophers; they were simply known as sages . The sage tradition provides an early glimpse of philosophical thought in action. Sages are sometimes associated with mathematical and scientific discoveries and at other times with their political impact. What unites these figures is that they demonstrate a willingness to be skeptical of traditions, a curiosity about the natural world and our place in it, and a commitment to applying reason to understand nature, human nature, and society better. The overview of the sage tradition that follows will give you a taste of philosophy’s broad ambitions as well as its focus on complex relations between different areas of human knowledge. There are some examples of women who made contributions to philosophy and the sage tradition in Greece, India, and China, but these were patriarchal societies that did not provide many opportunities for women to participate in philosophical and political discussions.

The Sages of India, China, Africa, and Greece

In classical Indian philosophy and religion, sages play a central role in both religious mythology and in the practice of passing down teaching and instruction through generations. The Seven Sages, or Saptarishi (seven rishis in the Sanskrit language), play an important role in sanatana dharma , the eternal duties that have come to be identified with Hinduism but that predate the establishment of the religion. The Seven Sages are partially considered wise men and are said to be the authors of the ancient Indian texts known as the Vedas. But they are partly mythic figures as well, who are said to have descended from the gods and whose reincarnation marks the passing of each age of Manu (age of man or epoch of humanity). The rishis tended to live monastic lives, and together they are thought of as the spiritual and practical forerunners of Indian gurus or teachers, even up to today. They derive their wisdom, in part, from spiritual forces, but also from tapas , or the meditative, ascetic, and spiritual practices they perform to gain control over their bodies and minds. The stories of the rishis are part of the teachings that constitute spiritual and philosophical practice in contemporary Hinduism.

Figure 1.2 depicts a scene from the Matsya Purana, where Manu, the first man whose succession marks the prehistorical ages of Earth, sits with the Seven Sages in a boat to protect them from a mythic flood that is said to have submerged the world. The king of serpents guides the boat, which is said to have also contained seeds, plants, and animals saved by Manu from the flood.

A scene from the Matsya Purana portrays Manu, the first man whose succession marks the prehistorical ages of earth. Manu sits with the Seven Sages in a boat to protect them from a mythic flood that is believed to have submerged the world.

Despite the fact that classical Indian culture is patriarchal, women figures play an important role in the earliest writings of the Vedic tradition (the classical Indian religious and philosophical tradition). These women figures are partly connected to the Indian conception of the fundamental forces of nature—energy, ability, strength, effort, and power—as feminine. This aspect of God was thought to be present at the creation of the world. The Rig Veda, the oldest Vedic writings, contains hymns that tell the story of Ghosha, a daughter of Rishi Kakshivan, who had a debilitating skin condition (probably leprosy) but devoted herself to spiritual practices to learn how to heal herself and eventually marry. Another woman, Maitreyi, is said to have married the Rishi Yajnavalkya (himself a god who was cast into mortality by a rival) for the purpose of continuing her spiritual training. She was a devoted ascetic and is said to have composed 10 of the hymns in the Rig Veda. Additionally, there is a famous dialogue between Maitreyi and Yajnavalkya in the Upanishads (another early, foundational collection of texts in the Vedic tradition) about attachment to material possessions, which cannot give a person happiness, and the achievement of ultimate bliss through knowledge of the Absolute (God).

Another woman sage named Gargi also participates in a celebrated dialogue with Yajnavalkya on natural philosophy and the fundamental elements and forces of the universe. Gargi is characterized as one of the most knowledgeable sages on the topic, though she ultimately concedes that Yajnavalkya has greater knowledge. In these brief episodes, these ancient Indian texts record instances of key women who attained a level of enlightenment and learning similar to their male counterparts. Unfortunately, this early equality between the sexes did not last. Over time Indian culture became more patriarchal, confining women to a dependent and subservient role. Perhaps the most dramatic and cruel example of the effects of Indian patriarchy was the ritual practice of sati , in which a widow would sometimes immolate herself, partly in recognition of the “fact” that following the death of her husband, her current life on Earth served no further purpose (Rout 2016). Neither a widow’s in-laws nor society recognized her value.

In similar fashion to the Indian tradition, the sage ( sheng ) tradition is important for Chinese philosophy. Confucius, one of the greatest Chinese writers, often refers to ancient sages, emphasizing their importance for their discovery of technical skills essential to human civilization, for their role as rulers and wise leaders, and for their wisdom. This emphasis is in alignment with the Confucian appeal to a well-ordered state under the guidance of a “philosopher-king.” This point of view can be seen in early sage figures identified by one of the greatest classical authors in the Chinese tradition, as the “Nest Builder” and “Fire Maker” or, in another case, the “Flood Controller.” These names identify wise individuals with early technological discoveries. The Book of Changes , a classical Chinese text, identifies the Five (mythic) Emperors as sages, including Yao and Shun, who are said to have built canoes and oars, attached carts to oxen, built double gates for defense, and fashioned bows and arrows (Cheng 1983). Emperor Shun is also said to have ruled during the time of a great flood, when all of China was submerged. Yü is credited with having saved civilization by building canals and dams.

Han Feizi is portrayed as a bearded man with black hair tied back into bun with a white ribbon gazing to the side with a determined glance.

These figures are praised not only for their political wisdom and long rule, but also for their filial piety and devotion to work. For instance, Mencius, a Confucian philosopher, relates a story of Shun’s care for his blind father and wicked stepmother, while Yü is praised for his selfless devotion to work. In these ways, the Chinese philosophical traditions, such as Confucianism and Mohism, associate key values of their philosophical enterprises with the great sages of their history. Whether the sages were, in fact, actual people or, as many scholars have concluded, mythical forebearers, they possessed the essential human virtue of listening and responding to divine voices. This attribute can be inferred from the Chinese script for sheng , which bears the symbol of an ear as a prominent feature. So the sage is one who listens to insight from the heavens and then is capable of sharing that wisdom or acting upon it to the benefit of his society (Cheng 1983). This idea is similar to one found in the Indian tradition, where the most important texts, the Vedas, are known as shruti , or works that were heard through divine revelation and only later written down.

Although Confucianism is a venerable world philosophy, it is also highly patriarchal and resulted in the widespread subordination of women. The position of women in China began to change only after the Communist Revolution (1945–1952). While some accounts of Confucianism characterize men and women as emblematic of two opposing forces in the natural world, the Yin and Yang, this view of the sexes developed over time and was not consistently applied. Chinese women did see a measure of independence and freedom with the influence of Buddhism and Daoism, each of which had a more liberal view of the role of women (Adler 2006).

A detailed and important study of the sage tradition in Africa is provided by Henry Odera Oruka (1990), who makes the case that prominent folk sages in African tribal history developed complex philosophical ideas. Oruka interviewed tribal Africans identified by their communities as sages, and he recorded their sayings and ideas, confining himself to those sayings that demonstrated “a rational method of inquiry into the real nature of things” (Oruka 1990, 150). He recognized a tension in what made these sages philosophically interesting: they articulated the received wisdom of their tradition and culture while at the same time maintaining a critical distance from that culture, seeking a rational justification for the beliefs held by the culture.

CONNECTIONS

The chapter on the early history of philosophy covers this topic in greater detail.

An older Laërtius with a long beard, heavy eyebrows, and a wool hat looks outward with a serious expression.

Among the ancient Greeks, it is common to identify seven sages. The best-known account is provided by Diogenes Laërtius, whose text Lives and Opinions of Eminent Philosophers is a canonical resource on early Greek philosophy. The first and most important sage is Thales of Miletus. Thales traveled to Egypt to study with the Egyptian priests, where he became one of the first Greeks to learn astronomy. He is known for bringing back to Greece knowledge of the calendar, dividing the year into 365 days, tracking the progress of the sun from solstice to solstice, and—somewhat dramatically—predicting a solar eclipse in 585 BCE. The eclipse occurred on the day of a battle between the Medes and Lydians. It is possible that Thales used knowledge of Babylonian astronomical records to guess the year and location of the eclipse. This mathematical and astronomical feat is one of Thales’s several claims to sagacity. In addition, he is said to have calculated the height of the pyramids using the basic geometry of similar triangles and measuring shadows at a certain time of day. He is also reported to have predicted a particularly good year for olives: he bought up all the olive presses and then made a fortune selling those presses to farmers wanting to turn their olives into oil. Together, these scientific and technical achievements suggest that at least part of Thales’s wisdom can be attributed to a very practical, scientific, and mathematical knowledge of the natural world. If that were all Thales was known for, he might be called the first scientist or engineer. But he also made more basic claims about the nature and composition of the universe; for instance, he claimed that all matter was fundamentally made of up water. He also argued that everything that moved on its own possessed a soul and that the soul itself was immortal. These claims demonstrate a concern about the fundamental nature of reality.

Another of the seven sages was Solon, a famed political leader. He introduced the “Law of Release” to Athens, which cancelled all personal debts and freed indentured servants, or “debt-slaves” who had been consigned to service based on a personal debt they were unable to repay. In addition, he established a constitutional government in Athens with a representative body, a procedure for taxation, and a series of economic reforms. He was widely admired as a political leader but voluntarily stepped down so that he would not become a tyrant. He was finally forced to flee Athens when he was unable to persuade the members of the Assembly (the ruling body) to resist the rising tyranny of one of his relatives, Pisistratus. When he arrived in exile, he was reportedly asked whom he considered to be happy, to which he replied, “One ought to count no man happy until he is dead.” Aristotle interpreted this statement to mean that happiness was not a momentary experience, but a quality reflective of someone’s entire life.

Beginnings of Natural Philosophy

The sage tradition is a largely prehistoric tradition that provides a narrative about how intellect, wisdom, piety, and virtue led to the innovations central to flourishing of ancient civilizations. Particularly in Greece, the sage tradition blends into a period of natural philosophy, where ancient scientists or philosophers try to explain nature using rational methods. Several of the early Greek schools of philosophy were centered on their respective views of nature. Followers of Thales, known as the Milesians , were particularly interested in the underlying causes of natural change. Why does water turn to ice? What happens when winter passes into spring? Why does it seem like the stars and planets orbit Earth in predictable patterns? From Aristotle we know that Thales thought there was a difference between material elements that participate in change and elements that contain their own source of motion. This early use of the term element did not have the same meaning as the scientific meaning of the word today in a field like chemistry. But Thales thought material elements bear some fundamental connection to water in that they have the capacity to move and alter their state. By contrast, other elements had their own internal source of motion, of which he cites the magnet and amber (which exhibits forces of static electricity when rubbed against other materials). He said that these elements have “soul.” This notion of soul, as a principle of internal motion, was influential across ancient and medieval natural philosophy. In fact, the English language words animal and animation are derived from the Latin word for soul ( anima ).

Similarly, early thinkers like Xenophanes began to formulate explanations for natural phenomena. For instance, he explained rainbows, the sun, the moon, and St. Elmo’s fire (luminous, electrical discharges) as apparitions of the clouds. This form of explanation, describing some apparent phenomenon as the result of an underlying mechanism, is paradigmatic of scientific explanation even today. Parmenides, the founder of the Eleatic school of philosophy, used logic to conclude that whatever fundamentally exists must be unchanging because if it ever did change, then at least some aspect of it would cease to exist. But that would imply that what exists could not exist—which seems to defy logic. Parmenides is not saying that there is no change, but that the changes we observe are a kind of illusion. Indeed, this point of view was highly influential, not only for Plato and Aristotle, but also for the early atomists, like Democritus, who held that all perceived qualities are merely human conventions. Underlying all these appearances, Democritus reasoned, are only atomic, unchanging bits of matter flowing through a void. While this ancient Greek view of atoms is quite different from the modern model of atoms, the very idea that every observable phenomenon has a basis in underlying pieces of matter in various configurations clearly connects modern science to the earliest Greek philosophers.

Along these lines, the Pythagoreans provide a very interesting example of a community of philosophers engaged in understanding the natural world and how best to live in it. You may be familiar with Pythagoras from his Pythagorean theorem, a key principle in geometry establishing a relationship between the sides of a right-angled triangle. Specifically, the square formed by the hypotenuse (the side opposite the right angle) is equal to the sum of the two squares formed by the remaining two sides. In the figure below, the area of the square formed by c is equal to the sum of the areas of the squares formed by a and b. The figure represents how Pythagoras would have conceptualized the theorem.

An illustration demonstrates the the ancient Greek philosopher Pythagoras' theorum on right triangles. It shows three squares arranged along the three sides of a right-angled triangle. The side of each square is equal to the side of the triangle to which it is connected. The e square connected to the hypotenuse, that is the side across from the right angle, of the triangle is visibly larger than the other two squares.

The Pythagoreans were excellent mathematicians, but they were more interested in how mathematics explained the natural world. In particular, Pythagoras recognized relationships between line segments and shapes, such as the Pythagorean theorem describes, but also between numbers and sounds, by virtue of harmonics and the intervals between notes. Similar regularities can be found in astronomy. As a result, Pythagoras reasoned that all of nature is generated according to mathematical regularities. This view led the Pythagoreans to believe that there was a unified, rational structure to the universe, that the planets and stars exhibit harmonic properties and may even produce music, that musical tones and harmonies could have healing powers, that the soul is immortal and continuously reincarnated, and that animals possess souls that ought to be respected and valued. As a result, the Pythagorean community was defined by serious scholarship as well as strict rules about diet, clothing, and behavior.

Additionally, in the early Pythagorean communities, it was possible for women to participate and contribute to philosophical thought and discovery. Pythagoras himself was said to have been inspired to study philosophy by the Delphic priestess Themistoclea. His wife Theano is credited with contributing to important discoveries in the realms of numbers and optics. She is said to have written a treatise, On Piety , which further applies Pythagorean philosophy to various aspects of practical life (Waithe 1987). Myia, the daughter of this illustrious couple, was also an active and productive part of the community. At least one of her letters has survived in which she discusses the application of Pythagorean philosophy to motherhood. The Pythagorean school is an example of how early philosophical and scientific thinking combines with religious, cultural, and ethical beliefs and practices to embrace many different aspects of life.

How It All Hangs Together

Closer to the present day, in 1962, Wilfrid Sellars, a highly influential 20th-century American philosopher, wrote a chapter called “Philosophy and the Scientific Image of Man” in Frontiers of Science and Philosophy . He opens the essay with a dramatic and concise description of philosophy: “The aim of philosophy, abstractly formulated, is to understand how things in the broadest possible sense of the term hang together in the broadest possible sense of the term.” If we spend some time trying to understand what Sellars means by this definition, we will be in a better position to understand the academic discipline of philosophy. First, Sellars emphasizes that philosophy’s goal is to understand a very wide range of topics—in fact, the widest possible range. That is to say, philosophers are committed to understanding everything insofar as it can be understood. This is important because it means that, on principle, philosophers cannot rule out any topic of study. However, for a philosopher not every topic of study deserves equal attention. Some things, like conspiracy theories or paranoid delusions, are not worth studying because they are not real. It may be worth understanding why some people are prone to paranoid delusions or conspiratorial thinking, but the content of these ideas is not worth investigating. Other things may be factually true, such as the daily change in number of the grains of sand on a particular stretch of beach, but they are not worth studying because knowing that information will not teach us about how things hang together. So a philosopher chooses to study things that are informative and interesting—things that provide a better understanding of the world and our place in it.

To make judgments about which areas are interesting or worthy of study, philosophers need to cultivate a special skill. Sellars describes this philosophical skill as a kind of know-how (a practical, engaged type of knowledge, similar to riding a bike or learning to swim). Philosophical know-how, Sellars says, has to do with knowing your way around the world of concepts and being able to understand and think about how concepts connect, link up, support, and rely upon one another—in short, how things hang together. Knowing one’s way around the world of concepts also involves knowing where to look to find interesting discoveries and which places to avoid, much like a good fisherman knows where to cast his line. Sellars acknowledges that other academics and scientists know their way around the concepts in their field of study much like philosophers do. The difference is that these other inquirers confine themselves to a specific field of study or a particular subject matter, while philosophers want to understand the whole. Sellars thinks that this philosophical skill is most clearly demonstrated when we try to understand the connection between the natural world as we experience it directly (the “manifest image”) and the natural world as science explains it (the “scientific image”). He suggests that we gain an understanding of the nature of philosophy by trying to reconcile these two pictures of the world that most people understand independently.

Read Like a Philosopher

“philosophy and the scientific image of man”.

This essay, “ Philosophy and the Scientific Image of Man ” by Wilfrid Sellars, has been republished several times and can be found online. Read through the essay with particular focus on the first section. Consider the following study questions:

What is the difference between knowing how and knowing that? Are these concepts always distinct? What does it mean for philosophical knowledge to be a kind of know-how?
What do you think Sellars means when he says that philosophers “have turned other special subject-matters to non-philosophers over the past 2500 years”?
Sellars describes philosophy as “bringing a picture into focus,” but he is also careful to recognize challenges with this metaphor as it relates to the body of human knowledge. What are those challenges? Why is it difficult to imagine all of human knowledge as a picture or image?
What is the scientific image of man in the world? What is the manifest image of man in the world? How are they different? And why are these two images the primary images that need to be brought into focus so that philosophy may have an eye on the whole?

Unlike other subjects that have clearly defined subject matter boundaries and relatively clear methods of exploration and analysis, philosophy intentionally lacks clear boundaries or methods. For instance, your biology textbook will tell you that biology is the “science of life.” The boundaries of biology are fairly clear: it is an experimental science that studies living things and the associated material necessary for life. Similarly, biology has relatively well-defined methods. Biologists, like other experimental scientists, broadly follow something called the “scientific method.” This is a bit of a misnomer, unfortunately, because there is no single method that all the experimental sciences follow. Nevertheless, biologists have a range of methods and practices, including observation, experimentation, and theory comparison and analysis, that are fairly well established and well known among practitioners. Philosophy doesn’t have such easy prescriptions—and for good reason. Philosophers are interested in gaining the broadest possible understanding of things, whether that be nature, what is possible, morals, aesthetics, political organizations, or any other field or concept.

1.1 What Is Philosophy?

Learning objectives.

By the end of this section, you will be able to:

Identify sages (early philosophers) across historical traditions.
Explain the connection between ancient philosophy and the origin of the sciences.
Describe philosophy as a discipline that makes coherent sense of a whole.
Summarize the broad and diverse origins of philosophy.

Historical Origins of Philosophy

The Sages of India, China, Africa, and Greece

In classical Indian philosophy and religion, sages play a central role in both religious mythology and in the practice of passing down teaching and instruction through generations. The Seven Sages, or Saptarishi (seven rishis in the Sanskrit language), play an important role in sanatana dharma , the eternal duties that have come to be identified with Hinduism but that predate the establishment of the religion. The Seven Sages are partially considered wise men and are said to be the authors of the ancient Indian texts known as the Vedas . But they are partly mythic figures as well, who are said to have descended from the gods and whose reincarnation marks the passing of each age of Manu (age of man or epoch of humanity). The rishis tended to live monastic lives, and together they are thought of as the spiritual and practical forerunners of Indian gurus or teachers, even up to today. They derive their wisdom, in part, from spiritual forces, but also from tapas , or the meditative, ascetic, and spiritual practices they perform to gain control over their bodies and minds. The stories of the rishis are part of the teachings that constitute spiritual and philosophical practice in contemporary Hinduism.

In similar fashion to the Indian tradition, the sage ( sheng ) tradition is important for Chinese philosophy . Confucius , one of the greatest Chinese writers, often refers to ancient sages, emphasizing their importance for their discovery of technical skills essential to human civilization, for their role as rulers and wise leaders, and for their wisdom. This emphasis is in alignment with the Confucian appeal to a well-ordered state under the guidance of a “ philosopher-king .” This point of view can be seen in early sage figures identified by one of the greatest classical authors in the Chinese tradition, as the “Nest Builder” and “Fire Maker” or, in another case, the “Flood Controller.” These names identify wise individuals with early technological discoveries. The Book of Changes , a classical Chinese text, identifies the Five (mythic) Emperors as sages, including Yao and Shun, who are said to have built canoes and oars, attached carts to oxen, built double gates for defense, and fashioned bows and arrows (Cheng 1983). Emperor Shun is also said to have ruled during the time of a great flood, when all of China was submerged. Yü is credited with having saved civilization by building canals and dams.

Connections

The chapter on the early history of philosophy covers this topic in greater detail.

Among the ancient Greeks, it is common to identify seven sages. The best-known account is provided by Diogenes Laërtius, whose text Lives and Opinions of Eminent Philosophers is a canonical resource on early Greek philosophy. The first and most important sage is Thales of Miletus . Thales traveled to Egypt to study with the Egyptian priests, where he became one of the first Greeks to learn astronomy. He is known for bringing back to Greece knowledge of the calendar, dividing the year into 365 days, tracking the progress of the sun from solstice to solstice, and—somewhat dramatically—predicting a solar eclipse in 585 BCE. The eclipse occurred on the day of a battle between the Medes and Lydians. It is possible that Thales used knowledge of Babylonian astronomical records to guess the year and location of the eclipse. This mathematical and astronomical feat is one of Thales’s several claims to sagacity. In addition, he is said to have calculated the height of the pyramids using the basic geometry of similar triangles and measuring shadows at a certain time of day. He is also reported to have predicted a particularly good year for olives: he bought up all the olive presses and then made a fortune selling those presses to farmers wanting to turn their olives into oil. Together, these scientific and technical achievements suggest that at least part of Thales’s wisdom can be attributed to a very practical, scientific, and mathematical knowledge of the natural world. If that were all Thales was known for, he might be called the first scientist or engineer. But he also made more basic claims about the nature and composition of the universe; for instance, he claimed that all matter was fundamentally made of up water. He also argued that everything that moved on its own possessed a soul and that the soul itself was immortal. These claims demonstrate a concern about the fundamental nature of reality.

Another of the seven sages was Solon , a famed political leader. He introduced the “Law of Release” to Athens, which cancelled all personal debts and freed indentured servants, or “debt-slaves” who had been consigned to service based on a personal debt they were unable to repay. In addition, he established a constitutional government in Athens with a representative body, a procedure for taxation, and a series of economic reforms. He was widely admired as a political leader but voluntarily stepped down so that he would not become a tyrant. He was finally forced to flee Athens when he was unable to persuade the members of the Assembly (the ruling body) to resist the rising tyranny of one of his relatives, Pisistratus. When he arrived in exile, he was reportedly asked whom he considered to be happy, to which he replied, “One ought to count no man happy until he is dead.” Aristotle interpreted this statement to mean that happiness was not a momentary experience, but a quality reflective of someone’s entire life.

Beginnings of Natural Philosophy

Similarly, early thinkers like Xenophanes began to formulate explanations for natural phenomena. For instance, he explained rainbows, the sun, the moon, and St. Elmo’s fire (luminous, electrical discharges) as apparitions of the clouds. This form of explanation, describing some apparent phenomenon as the result of an underlying mechanism, is paradigmatic of scientific explanation even today. Parmenides, the founder of the Eleatic school of philosophy, used logic to conclude that whatever fundamentally exists must be unchanging because if it ever did change, then at least some aspect of it would cease to exist. But that would imply that what exists could not exist—which seems to defy logic. Parmenides is not saying that there is no change, but that the changes we observe are a kind of illusion. Indeed, this point of view was highly influential, not only for Plato and Aristotle, but also for the early atomists, like Democritus , who held that all perceived qualities are merely human conventions. Underlying all these appearances, Democritus reasoned, are only atomic, unchanging bits of matter flowing through a void. While this ancient Greek view of atoms is quite different from the modern model of atoms, the very idea that every observable phenomenon has a basis in underlying pieces of matter in various configurations clearly connects modern science to the earliest Greek philosophers.

How It All Hangs Together

Closer to the present day, in 1962, Wilfrid Sellars , a highly influential 20th-century American philosopher, wrote a chapter called “Philosophy and the Scientific Image of Man” in Frontiers of Science and Philosophy . He opens the essay with a dramatic and concise description of philosophy: “The aim of philosophy, abstractly formulated, is to understand how things in the broadest possible sense of the term hang together in the broadest possible sense of the term.” If we spend some time trying to understand what Sellars means by this definition, we will be in a better position to understand the academic discipline of philosophy. First, Sellars emphasizes that philosophy’s goal is to understand a very wide range of topics—in fact, the widest possible range. That is to say, philosophers are committed to understanding everything insofar as it can be understood. This is important because it means that, on principle, philosophers cannot rule out any topic of study. However, for a philosopher not every topic of study deserves equal attention. Some things, like conspiracy theories or paranoid delusions, are not worth studying because they are not real. It may be worth understanding why some people are prone to paranoid delusions or conspiratorial thinking, but the content of these ideas is not worth investigating. Other things may be factually true, such as the daily change in number of the grains of sand on a particular stretch of beach, but they are not worth studying because knowing that information will not teach us about how things hang together. So a philosopher chooses to study things that are informative and interesting—things that provide a better understanding of the world and our place in it.

Read Like a Philosopher

“philosophy and the scientific image of man”.

What is the difference between knowing how and knowing that? Are these concepts always distinct? What does it mean for philosophical knowledge to be a kind of know-how?
What do you think Sellars means when he says that philosophers “have turned other special subject-matters to non-philosophers over the past 2500 years”?
Sellars describes philosophy as “bringing a picture into focus,” but he is also careful to recognize challenges with this metaphor as it relates to the body of human knowledge. What are those challenges? Why is it difficult to imagine all of human knowledge as a picture or image?
What is the scientific image of man in the world? What is the manifest image of man in the world? How are they different? And why are these two images the primary images that need to be brought into focus so that philosophy may have an eye on the whole?

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Access for free at https://openstax.org/books/introduction-philosophy/pages/1-introduction

Authors: Nathan Smith
Publisher/website: OpenStax
Book title: Introduction to Philosophy
Publication date: Jun 15, 2022
Location: Houston, Texas
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Socrates was an ancient Greek philosopher considered to be the main source of Western thought. He was condemned to death for his Socratic method of questioning.

Who Was Socrates?

When the political climate of Greece turned against him, Socrates was sentenced to death by hemlock poisoning in 399 B.C. He accepted this judgment rather than fleeing into exile.

Early Years

Born circa 470 B.C. in Athens, Greece, Socrates's life is chronicled through only a few sources: the dialogues of Plato and Xenophon and the plays of Aristophanes.

Because these writings had other purposes than reporting his life, it is likely none present a completely accurate picture. However, collectively, they provide a unique and vivid portrayal of Socrates's philosophy and personality.

Socrates was the son of Sophroniscus, an Athenian stonemason and sculptor, and Phaenarete, a midwife. Because he wasn't from a noble family, he probably received a basic Greek education and learned his father's craft at a young age. It's believed Socrates worked as mason for many years before he devoted his life to philosophy.

Contemporaries differ in their account of how Socrates supported himself as a philosopher. Both Xenophon and Aristophanes state Socrates received payment for teaching, while Plato writes Socrates explicitly denied accepting payment, citing his poverty as proof.

Socrates married Xanthippe, a younger woman, who bore him three sons: Lamprocles, Sophroniscus and Menexenus. There is little known about her except for Xenophon's characterization of Xanthippe as "undesirable."

He writes she was not happy with Socrates's second profession and complained that he wasn’t supporting family as a philosopher. By his own words, Socrates had little to do with his sons' upbringing and expressed far more interest in the intellectual development of Athens' other young boys.

Life in Athens

Athenian law required all able-bodied males serve as citizen soldiers, on call for duty from ages 18 until 60. According to Plato, Socrates served in the armored infantry — known as the hoplite — with shield, long spear and face mask.

He participated in three military campaigns during the Peloponnesian War , at Delium, Amphipolis and Potidaea, where he saved the life of Alcibiades, a popular Athenian general.

Socrates was known for his fortitude in battle and his fearlessness, a trait that stayed with him throughout his life. After his trial, he compared his refusal to retreat from his legal troubles to a soldier's refusal to retreat from battle when threatened with death.

Plato's Symposium provides the best details of Socrates' physical appearance. He was not the ideal of Athenian masculinity. Short and stocky, with a snub nose and bulging eyes, Socrates always seemed to appear to be staring.

However, Plato pointed out that in the eyes of his students, Socrates possessed a different kind of attractiveness, not based on a physical ideal but on his brilliant debates and penetrating thought.

Socrates always emphasized the importance of the mind over the relative unimportance of the human body. This credo inspired Plato’s philosophy of dividing reality into two separate realms, the world of the senses and the world of ideas, declaring that the latter was the only important one.

Socrates believed that philosophy should achieve practical results for the greater well-being of society. He attempted to establish an ethical system based on human reason rather than theological doctrine.

Socrates pointed out that human choice was motivated by the desire for happiness. Ultimate wisdom comes from knowing oneself. The more a person knows, the greater his or her ability to reason and make choices that will bring true happiness.

Socrates believed that this translated into politics with the best form of government being neither a tyranny nor a democracy. Instead, government worked best when ruled by individuals who had the greatest ability, knowledge and virtue, and possessed a complete understanding of themselves.

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Socratic Method

For Socrates, Athens was a classroom and he went about asking questions of the elite and common man alike, seeking to arrive at political and ethical truths. Socrates didn’t lecture about what he knew. In fact, he claimed to be ignorant because he had no ideas, but wise because he recognized his own ignorance.

He asked questions of his fellow Athenians in a dialectic method — the Socratic Method — which compelled the audience to think through a problem to a logical conclusion. Sometimes the answer seemed so obvious, it made Socrates' opponents look foolish. For this, his Socratic Method was admired by some and vilified by others.

During Socrates' life, Athens was going through a dramatic transition from hegemony in the classical world to its decline after a humiliating defeat by Sparta in the Peloponnesian War. Athenians entered a period of instability and doubt about their identity and place in the world.

As a result, they clung to past glories, notions of wealth and a fixation on physical beauty. Socrates attacked these values with his insistent emphasis on the greater importance of the mind.

While many Athenians admired Socrates' challenges to Greek conventional wisdom and the humorous way he went about it, an equal number grew angry and felt he threatened their way of life and uncertain future.

Trial of Socrates

In 399 B.C., Socrates was accused of corrupting the youth of Athens and of impiety, or heresy. He chose to defend himself in court.

Rather than present himself as wrongly accused, Socrates declared he fulfilled an important role as a gadfly, one who provides an important service to his community by continually questioning and challenging the status quo and its defenders.

The jury was not swayed by Socrates' defense and convicted him by a vote of 280 to 221. Possibly the defiant tone of his defense contributed to the verdict and he made things worse during the deliberation over his punishment.

Athenian law allowed a convicted citizen to propose an alternative punishment to the one called for by the prosecution and the jury would decide. Instead of proposing he be exiled, Socrates suggested he be honored by the city for his contribution to their enlightenment and be paid for his services.

The jury was not amused and sentenced him to death by drinking a mixture of poison hemlock.

Socrates' Death

Before Socrates' execution, friends offered to bribe the guards and rescue him so he could flee into exile.

He declined, stating he wasn't afraid of death, felt he would be no better off if in exile and said he was still a loyal citizen of Athens, willing to abide by its laws, even the ones that condemned him to death.

Plato described Socrates' execution in his Phaedo dialogue: Socrates drank the hemlock mixture without hesitation. Numbness slowly crept into his body until it reached his heart. Shortly before his final breath, Socrates described his death as a release of the soul from the body.

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philosophy of life

noun phrase

Definition of philosophy of life, examples of philosophy of life in a sentence.

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'philosophy of life.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

1760, in the meaning defined at sense 1

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Cite this Entry

“Philosophy of life.” Merriam-Webster.com Dictionary , Merriam-Webster, https://www.merriam-webster.com/dictionary/philosophy%20of%20life. Accessed 12 May. 2024.

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Leadership lessons from the late great philosopher daniel dennett.

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Daniel C. Dennett, University Professor and Austin B. Fletcher Professor of Philosophy, and Director ... [+] of the Center for Cognitive Studies at Tufts University, photographed in his office at Tufts. (Photo by Rick Friedman/Corbis via Getty Images)

The polymath Daniel Dennett passed away last month at the age of 82. The son of the first C.I.A. agent killed in the line of duty, Dennett lived a remarkable life.

This was true philosophically; he earned philosophy degrees at Harvard and Oxford under the two men who set the philosophical standard in the English speaking world at the time: William V.O. Quine at Harvard and Gilbert Ryle at Oxford. Aided by these giants’ recommendations, Dennett was offered a tenure-track professor position in the U.S. before even earning a PhD, strictly fairytale by today’s standards. He went on to spend the majority of his career at Tufts University, now widely believed to have the top philosophy master’s program in the world.

This was also true away from the classroom. Dennett owned and operated a farm in Maine for upwards of 40 years, building and fixing the property from humble beginnings before trading it in for a smaller, coastal home. He was also a classically trained musician and singer, as well as an avid traveler and sailor. Any philosopher, biologist, cognitive scientist, sailor, farmer, musician, neurologist, or psychologist (among many other professions) can find some pertinent and revealing information for their own life in the work of this uniquely modern philosopher. His life is also an excellent guide for leaders of every stripe.

Here are three leadership lessons from the life and work of Daniel Dennett.

Be Open To Collaborating With Outsiders

Academic life is often siloed. Faculty and students tend to only interact with people within the same department, or at the very least in the same field. This phenomenon is even more magnified with philosophy; there is a divide between ‘analytic’ and ‘continental’ where philosophers who identify with one side will pay little to no attention to what the other side is working on, even suggesting their work is something other than philosophy.

Dennett was a significant exception to this rule. Speaking of his fellow philosophers, Dennett explained that he has “grown accustomed to the disrespect…for their colleagues in other disciplines.”

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From an early age, he collaborated with people outside of his field, often to the condemnation of other philosophers. Importantly, this cooperation led him to some of his most successful enterprises. One example is Dennett’s longtime partnership with computer scientist Doug Hofstadter, formally beginning with the 1981 collection of essays titled The Mind’s I.

The benefits of collaborating with outsiders are plentiful, especially for a leader. Working with someone with other areas of expertise makes expanding your knowledge and the scope of your work easier. It will spark new ways to look at your own ideas, allowing possible issues to more readily present themselves. Furthermore, as a leader, people within your own world may be hesitant to disclose possible issues to you in the first place, but an outsider will be more inclined to do so.

Stay Firm In Your Beliefs

Dennett faced countless objections to his work throughout his career, partially because of his willingness to work with others but also because of his unorthodox ideas.

As a young scholar, Dennett described his lifelong project as such: “figuring out as a philosopher, how brains could be, or support, or explain, or cause, minds.” This meant Dennett espoused physicalism, the concept that consciousness can be explained purely physically all the way down. In other words, there is no intangible ‘soul’ or ‘mind’ that comes with our subjective experience. It should be understood only in terms of physical processes in the brain. Dennett was not the first physicalist, but he championed using science to explain his philosophical theories about the mind, famously found in his 1991 book Consciousness Explained.

This view of the mind is opposed to dualism, or the idea that there is something non-physical within us. Dualism is still the popular belief today, but that did not stop Dennett from spending a career advocating for his physicalist model. It would have been much easier for him to accept his critics and focus on one of his many other areas of interest, such as free will and atheism. But he stood firm in his beliefs, begetting an entire school of thought (as well as a Center for Cognitive Studies at Tufts) who follow Dennett’s path of merging brain science and philosophy.

Importantly, Dennett did not just believe his theories but provided vast amounts of examples and conducted many experiments that backed them up. This gave his beliefs strength and allowed him to grow a following as he stood firm. A leader can replicate this process to gain followers: form beliefs and back them up with hard evidence. Then, when you do not bend to your critics, you will show strength and prove to others why you deserve to be a leader.

Take A Step Back

The “publish or perish” mentality of academia can be daunting. It can force scholars to believe there is no time to take any sort of break. And if you do, it’s fall behind or get left behind. The mindset of a leader can be similar. If you take a momentary step back, people may question your leadership or try to seal your position of authority.

These possibilities did not stop Dennett from shifting away from philosophical work into what he called “tillosophy.” He would usually practice tillosophy over the summer months at his farm. In his 2023 memoir I’ve Been Thinking, Dennett talks about his tillosophical process.

“I’d spend twenty minutes at my desk, packing my head with a philosophical problem that had been puzzling me, and then go out and hop on the tractor or paint the barn or mow the hayfield or pick berries or cut firewood…I don’t even think about the problem…and as often as not have a breakthrough before I came in for lunch or supper.”

Daniel C. Dennett gave so much to the world of philosophy of mind, but he has so much to offer to all possible worlds, even as a skeptic of their possibilities.

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Open a textbook in biology and you’ll find a purported definition of life, usually in the form of a list of characteristics that apply to organisms, their parts, their interactions, or their history. Often these definitions will be nothing more than descriptions or rely on more controversial theoretical commitments.

Like many basic concepts, it is difficult to non-controversially define life. Most people simply avoid the issue by ignoring marginal cases, accepting the vagueness of the boundary cases, or setting aside the whole issue as beyond their scope. Nonetheless, there are many people whose work seems to require a rigorous demarcation of life, especially in new scientific contexts, such as astrobiology, origins of life, or synthetic biology. As such, the nature of life continues to be a hotly debated topic.

This article focuses on the subject matter of biology: life. The first half of this article will focus on attempts to characterize life by both philosophers and scientists. The first section will describe alternative accounts of definitions, its two subsections will cover historical and contemporary definitions, and section 2 covers the recent countertrend in skepticism toward definitions of life. Because the various stakeholders have different goals, the second half will focus on those goals. Sections 3, 4, and 5 cover topics that some believe require a definition of life: artificial and synthetic life, the origin(s) of life, and the search for life in the Universe. Section 6 covers entities that are much larger or smaller than organisms, while section 7 covers the role life takes in the context of society, especially with respect to questions raised by new technology.

1.1 Definitions of Life from Antiquity to Darwin

1.2 contemporary definitions of life, 2. definitional skepticism, 3. artificial and synthetic life, 4. origin(s) of life, 5. search for life, 6. the macro and the micro perspectives, 7. ethics, law, and politics, 8. conclusion, other internet resources, related entries, 1. definition(s).

Few things in biology have been more extensively discussed than the definition of life. It is frustrating so little progress has been made on the topic in the face of so much research, theory, and debate. There are many reasons for this failure: disagreements about how abstract or specific definitions should be, different commitments as to what ought to be included in a definition, and even disagreement about the nature of definitions themselves. This section covers the nature and role of definitions. Each of these has been used in approaching the question of life.

Historically, when philosophers and scientists define a concept, the aim is to provide necessary and sufficient conditions. These theoretical definitions (also called real , ideal or philosophical definitions) are often impractical or fragile as they can be challenged with a single imagined counterexample. A classic case is the definition of “bachelors” as “unmarried males.” It is trivial to find examples that fit this definition without intuitively being bachelors: male dogs, baby boys, widowers, etc. Similarly, for any definition of life, one can either show living cases that are left out of the definition or non-living cases that are included by it. Life is organized, but so are geological formations. Life processes energy, but so does fire. Life evolves using complex biochemistry, but so do prions. Life is self-sustaining, but parasites are not. Life is at thermodynamic disequilibrium, but so is much else. As we’ll see shortly, perhaps theoretical definitions are too rigid a standard. The real world is far too complex for limited criteria to decide every marginal case.

Non-philosophers are typically quite frustrated by the back-and-forth that results from theoretical definitions. To that end, some favor operational (or working ) definitions, ones that work in practice to narrow down the range of phenomena under consideration. This approach is often not considered a kind of definition by philosophers (see Gupta 2021). Operational definitions tend to be philosophically shallow. For example, NASA’s operational definition of life as “a self-sustaining chemical system capable of Darwinian evolution” (Joyce 1994) might include viruses while excluding mules. The lack of depth of an operational definition can frustrate theoretically minded people, including other scientists.

There are several other conceptions of definition, as well. The nominal (also lexicographer or dictionary ) definition is determined by analyzing usage. It will not work for cutting edge or controversial issues because such definitions follow the slow process of cultural acceptance rather than provide guidance to researchers at the forefront of these debates. Scholars are more likely to quote a dictionary definition than be illuminated by one.

There are also demonstrative or ostensive definitions, which are concepts we can convey by mere shared observations: “that is red” while pointing at a red object, for instance. Potter Stewart famously defined pornography in this manner by saying “I know it when I see it” (Stewart 1964). Knowledge by ostension may reflect epistemic access to a natural kind, although this may feel indistinguishable from an internalized cultural category. There is huge variation among what scientists consider ‘life,’ even among objects on Earth, like viruses and prions, which suggests this kind of definition is not viable for this target.

Then there are stipulative definitions, which are terms introduced and defined by fiat. A circle in Euclidean geometry can be defined as a round plane figure whose boundary consists of infinite points equidistant to a single other point. There are no possible counterexamples to this definition, given the axioms of Euclidean geometry. This approach provides little refuge in the real world. Consider an attempt to define swans as “white birds with long necks.” By stipulation, storks, great egrets, and many cranes would be swans, while Australia’s black swans would not. Such a quick and dirty definition seems to define the category out of hand and perhaps only works within accepted axioms or theories. Life could be stipulated as “carbon-based reproducing entities,” which would rule out silicon-based life by fiat. Such a definition merely pushes the debate to the scenarios in which the stipulated definition goes against intuitive notions.

The 20th century saw some steps away from definitions toward alternative views of concepts, notably prototypes , exemplars , and theories (Machery 2009). Prototype concepts are abstract features shared by most, but not all members of a category (Rosch & Mervis 1975; Rosch 1978; Hampton 1979, 2006; Smith 2002). The definitions of life in biology textbooks might be charitably understood as prototype concepts. So, too, are the property cluster natural kinds popular in philosophy of biology (Boyd 1991, 1999, 2010; Diguez 2013; Slater 2015). Exemplars are concepts built around similarity to a particular individual case (Medin & Schaffer 1978, Nosofsky 1986). Both prototypes and exemplar concepts rely on similarity to paradigmatic cases, with the former being an imagined ideal and the latter being a real instance (Komatsu 1992). For similarity-based concepts to work in scientific cases such as life, we need an account of which similarities matter, how much, and why. In contrast to similarity-based concepts, the requirements of theory concepts are somewhat more nebulous. Theory concepts are modeled on scientific theories and thus reflect their diversity (Carey 1985, Murphy & Medin 1985, Gopnik & Meltzoff 1997). At the core, theory concepts rely on explanations for why the members of a category share certain properties. Marginal cases of life, such as viruses, prions, or protocells, might be included in some theories of life but not others.

In sum, there are many potential approaches to definitions, each with different benefits, drawbacks, and standards of success. Much more could be said about these and other possible approaches, but this will suffice for our purposes. Some of the disagreements about defining life dissolve upon clarifying which type of definition or concept is being used. Many of the explicit attempts to define life have focused on either operational and philosophical definitions, while often not acknowledging or misunderstanding the distinction between these. One will note these two definitions are at cross-purposes – operational definitions can be quick and dirty, but philosophical definitions seek to give necessary and sufficient conditions. Less work has been done on life as a non-definitional concept, although that is perhaps changing.

This subsection briefly explores historical definitions of life. There are more in depth treatments of the matter, to which an interested reader should turn (Bedau & Cleland 2010, Riskin 2015, Mix 2018). Approaches to this issue vary widely across historians, philosophers, and scientists, so some skepticism about any individual author’s approach to the topic is warranted.

We begin with the Greeks. In several dialogues, notably the Phaedrus , Timeaus , and Republic , Plato divided life into three parts: vegetable life, animal life, and rational life. All living creatures possessed the first in the form of nutrition and reproduction, animals were additionally capable of sensation and locomotion, and humans also had rational souls. Plato’s subsequent influence in Christian theology may be apparent in spirit if not in detail. In Christian theology, human life was not only rational, but also involved an eternal, spiritual soul and an internal, conscious life.

Plato’s student, Aristotle, had a different notion in which living things had an appropriate form, material, and goal-directedness ( De Anima , 412a1–416b). Aristotle held life to be a form of self-motion, perpetuation, or self-alteration (Byers 2006). For Aristotle, the capacity to resist internal and external perturbations was the essential distinction between living beings and non-living objects. Other features were accidental. This quest for demarcating the essential from the accidental for life has persisted to this day in searches for theoretical definitions of life as well as in attacks against those not interested in such definitions.

Centuries later, Descartes drew a sharper distinction between animal life and rational life than between inanimate objects and animal life. This was a turn away from medieval approaches, which had taken the gap between vegetables and animals to be broader. For Descartes, animals are analogous to complex clocks and lack the inner or spiritual life central to the human experience (Descartes 2010/1664). As such, Descartes’ category of life neither mapped onto Greek conceptions nor current conceptual frameworks. The mechanistic view developed by Descartes and his followers is often thought to be continuous with current scientific thinking, but this is perhaps anachronistic, as much of the theoretical underpinning separating animal life and rational life is no longer accepted.

The responses to Descartes came to be grouped under the heading ‘vitalism.’ Vitalism, which spanned three centuries, was a heterogenous philosophical position unified by adherents’ doubt of a fully mechanistic view of life. Vitalists had ontologies of defining features of life as varied as immaterial causes, particular arrangements of matter, a special life fluid, a particular end goal, or even mental forces. A whiggish history of biology will declare the death of vitalism with Friedrich Wöhler’s synthesis of urea from ammonium cyanate. The suggestion is that if biological chemicals can be produced from mere chemistry, then biology is also mere chemistry. Although this was an important step, many chemists already had accepted a mechanistic world view, and many other researchers continued to develop vitalist theories well into the 20th century (Bergson 1959, Driesch 1905/1914).

The 20th century largely saw the mechanist/vitalist divide dissipate. Despite the difficulties described above about definitions, hundreds of scientists, philosophers, and others have tried their hand at defining life. Much of the interest is motivated by new science and new technologies – including artificial life, synthetic biology, origins of life, and astrobiology – which complicate the issue by violating some of the traditional groupings of properties associated with life. There are numerous books, articles, and workshops on the nature of life (Pályi et al. 2002, Popa 2004, Bedau & Cleland 2010).

Table 1. Some recent attempts at meta-categories for life definitions. Each column is one account’s categories, the rows are lined up according to rough similarity.

There are perhaps thousands of competing definitions proposed across hundreds of articles. A true survey of that variety would be beyond the scope of this article and beyond your patience as a reader. Nevertheless, some broad categories have been proposed that might offer some insight into current contending definitions. Table 1 summarizes three of the most rigorous attempts this century to categorize definitions of life.

Each of these authors used different approaches to arrive at their categories. Popa 2004 and Trifonov 2011 attempted to reverse engineer the categories from dozens of definitions collected from many dozens of experts, while Malaterre and Chartier 2019 conducted a more extensive, text-mining approach across 30,000 scientific articles selected from journals that published pieces in biology. As one can see, there are areas of rough overlap, but each categorization scheme has its own unique categories as well.

Most of the definitions considered by these authors straddle some of these distinctions and are often ambiguous as to whether they are intended to be theoretical definitions, operational definitions, or something else. For example, Popa 2004 considers definitions ranging from Oparin 1961’s “Any system capable of replication and mutation is alive” to Schulze-Makuch et al. 2002:

We propose to define living systems as those that are: (1) composed of bounded micro-environments in thermodynamic equilibrium with their surroundings; (2) capable of transforming energy to maintain their low-entropy states; and (3) able to replicate structurally distinct copies of themselves from an instructional code perpetuated indefinitely through time despite the demise of the individual carrier through which it is transmitted.

Categorizing definitions such as these necessarily requires some choices and reasonable people can disagree about whether each belongs in one or more categories.

The takeaway from current understandings of the definition of life is that there is no consensus forthcoming in the near future. One concern is that these are summaries of attempts to define a category for which there is only loose agreement. Many scientists disagree as to the phenomena a definition of life is intended to unify. Some scientists would include prions, viruses, and entities only hypothesized to exist in the origin of life, while others would completely reject them. Some might accept digital organisms as alive, others would deny this approach. Conceptual equivocation could have significant costs for research. One field recently quantified this cost, suggesting it is more than a merely theoretical concern (Trombley and Cottenie 2019). Given the diversity described above, one may be tempted to adopt a definitional pluralism : there are many ways to be alive. For some reason, that approach is not common in the literature.

Nearly everybody agrees there is a distinction between life and non-life, typically understood as a difference in kind rather than one of degree. Furthermore, most people involved accept that life is some sort of natural kind, rather than a human psychological concept. That said, a common theme in recent philosophical work has been to express skepticism of life definitions as a goal. The literature on the definition of life is vast, repetitive, and utterly inconclusive. Philosophers have disagreed as to the ultimate source of the lack of consensus, citing unstated assumptions in either the definer’s approach or the question itself. Note that many scientists are less likely to be skeptical of the goal of defining life, though also more resistant to engaging in the philosophical debate.

One skeptical view has arisen from the observation that theoretical definitions of life presume a theory of life (Cleland and Chyba 2002, Benner 2010, Cleland 2019). Although it is not obvious that the authors allude to the theory-theory of concepts, described in section 1, a common analogy is to early chemical theory. According to this analogy, early alchemists likened the alchemists’ Aqua regia (“royal water”) and Aqua fortis (“strong water”). Development of atomic theory revealed, Cleland argues, that the true nature of water was H 2 O, while the other ‘waters’ were HNO 3 + 3 HCl and HNO 3 , respectively. Cleland advocates avoiding definitions altogether, fearing they will blind us to new instances of life, and instead opts for tentative criteria, which she believes avoid the implicit dogma of even operational definitions.

Other authors have pointed out that the explanandum of life is itself up for debate (Tsokolov 2009, Mix 2020, Parke 2020). According to Emily Parke, some accept life as applying to individuals, whereas other definitions apply to collectives first (including entire planets) and individuals derivatively. Relatedly, most believe life is some kind of entity rather than some kind of relation or process (but see Nicholson and Dupré 2018). Parke also points out that some definitions seek a material basis, perhaps limiting life’s substrate to the biochemistry we know on Earth, while others are functional. Sagan famously worried about biochemical definitions because they were prone to ‘Earth Chauvinism’ for privileging our own biochemistry (1970). Other authors take our biochemistry to be independently justified as universal (Pace 2001, Benner et al. 2004, but see Bains 2004). Finally, Parke distinguishes between those that seek clean boundaries and those that accept the possibility of a continuum of ‘lifelikeness.’

Other authors have advocated a kind of quietism about definitions, maintaining that folk concepts need not match up with scientific ones (Machery 2011), any definitions would not change scientific practice (Szostak 2012), advocated a radical conceptual rethinking (Mariscal & Doolittle 2020), or denied the distinction between life & non-life entirely (Jabr 2013).

This last position of eliminativism could be expanded as it helps illustrate all other life skeptical positions. Cowie 2009 classifies eliminativist goals as either linguistic or ontological. Ontological eliminativists don’t believe the objects they are eliminating truly exist. We’re all eliminativists about something, perhaps ghosts or fairies. Linguistic/conceptual eliminativists, on the other hand are merely suspicious of theoretical terms or concepts, what Ramsey 2020 calls ‘category dissolution’ or ‘conceptual fragmentation.’ In essence, it’s not that there aren’t living things, it’s just that the category life is heterogeneous rather than a natural kind. According to Cowie, one can deny that anything matching our theoretical definition of life actually exists in the world while still accepting it as a useful fiction. Conversely, one may think scientific theories about life are fruitless or that the term is too vague and confused to be useful, without doubting life exists. If we accept any of these alternatives, we should perhaps avoid ever using the term ‘life’ in isolation and instead reference Metabolic Life and Evolutionary Life and all the other conceptions.

At play in these various forms of skepticism are several underlying assumptions. Among other disagreements, researchers disagree about what life is, whether it is a natural kind with an essence or a human construct; they disagree as to the purpose of defining life, especially if it will not change scientific practice; and they disagree as to the features of life that are relevant and the ones that are mere consequences. When researchers hold unstated assumptions such as these, they are liable to mistake the source of their disagreement.

The rest of this article will focus on uses of the various life concepts. Some of the definitions described above are derived from, or necessary for, specific scientific and societal purposes. This section focuses on artificial and synthetic life.

In principle, most contemporary scientists and philosophers believe life can be created, but there is broad disagreement as to what needs to be recreated for something to be life. In functional approaches, mere formal organization sufficiently similar to organisms may be enough. Complexly configured robots (“hardware”) or computer programs (“software”) might qualify. This view is known as Strong Artificial Life (A-Life for short) and has received much of the same pushback as the Strong Artificial Intelligence approach before it (Sober 1991, Boden 1999, Brooks 2001). Those who reject the Strong A-Life view believe that functional approaches miss some of the essential features of biology for either epistemic or ontological reasons. Epistemic objections might be consistent with the possibility of Strong A-Life, but doubt that we have the knowledge to recreate the relevant biological functions in a digital framework. Conversely, most of the objections to Strong A-Life have been ontological, resting on the view that representations cannot be equivalent to that which they represent and that perhaps life requires chemical embodiment, ruling Strong A-Life impossible by fiat.

Weak A-Life approaches, on the other hand, don’t presume the ontological equivalence of structurally similar circuits and cells. Instead, proponents suggest the more modest goal of developing a deeper understanding of life as we know it by exploring the effects of various parameters in simulations, effectively placing life in a broader context of possible biology (Langton 1989, 1995). For example, in the Terra program, software was pitted against other software for processing power (Ray 1993). Unexpected by the researchers at the time, software parasitism evolved: software would co-opt the reproductive processing of other software. Policing mechanisms also evolved, leading to an arms race between free-riders and the software trying to stop them.

Whether one accepts the strong or weak interpretation of A-Life, these in silico approaches are cheaper than equivalent work done in real organisms. They also offer possibilities that are not available in ordinary biology, such as programming alternative parameters to take the place of laws of nature and exploring relationships across deep time and space quickly and efficiently.

Another approach worth highlighting is that of synthetic life (“wetware”). Less conceptually troubled, synthetic life can also address some questions of A-Life, while allowing for a finer grain of realism. Synthetic life approaches have explored creating self-replication (Lincoln & Joyce 2009), minimal genomes (Koonin 2000, Hutchinson et al. 2016), a chemical evolution (Gromski et al. 2020), and other projects. Not all synthetic biology is in the business of investigating life as it could be, as not all computer programming is A-Life. Nevertheless, the tools developed by both can be illuminating. By exploring possibilities, scientists can discover previously hidden relationships, revealing which aspects of life are more or less plausible than expected.

Inextricable from the question of life’s nature is the question of its origin. Ancient and modern thinkers accepted that life often arose spontaneously from non-life. Two centuries of experiments eventually overturned this widely accepted view, culminating in Louis Pasteur’s swan-neck bottle experiments. Since then, the puzzle of Life’s origin has been one of the biggest and most important in all of science.

Darwin was famously silent about the problem, although in a letter to his friend Joseph Hooker, Darwin confided that he imagined life originating in “some warm little pond” (see Other Internet Resources below; and Peretó et al. 2009). Subsequent work on the subject was sparse until the 1920s when Alexander Oparin and J.B.S. Haldane independently proposed hypotheses for life’s origin in then plausible early Earth conditions (Haldane 1929; Oparin 2010/1936). As a graduate student in the 1950s, Stanley Miller tested the proposal, discovering dozens of amino acids in the mixture (1953). Since then, the field of origins-of-life studies has expanded dramatically.

Our earliest reliable records of this planet, some 3.5 billion years ago, contain distinctive evidence of microbial fossils, including distinctive shapes that correlate to the sizes and shapes of current prokaryotes, as well as carbon-ratios distinctive to life as we know it (Schopf 1993, Schopf et al. 2017). Many analyses have pushed our confidence in life’s earlier origin significantly further back, suggesting that basically as soon as Earth was not molten, it was filled with life (Pearce et al. 2018, Lineweaver 2020). How life started and why it started so quickly remains one of the most pressing open questions in science.

There are many open philosophical issues in origins of life research. Several of these are centered around the explanandum in question and epistemological limits to our knowledge. Researchers differ, for example, as to whether the purpose of origins-of-life research is to discover how life could have originated or how it did originate (Scharf et al. 2015, Mariscal et al. 2019). Some steps in the process could have been chancy, others could have been deterministic but highly contingent, still others could have been the only way life ever originates anywhere in the Universe.

There are several broad approaches to investigating the origin of life. “Bottom-Up” approaches begin with pre-biotic chemistry and explore how it could withstand stressors in order for lifelike entities to form and evolve. At present, there are many unsolved problems, most notably that most energetically favorable interactions would consume the proto-life forms involved. Scientists have cleverly attempted to ease the problem by relaxing assumptions: perhaps the environment provided our first boundaries (Koonin 2009), or perhaps it provided porto-genetic material (Mathis et al. 2017), all of this could have occurred in a viscous solvent instead of a cell (He et al. 2017), or on a surface (Wächtershäuser 1988), or using a variety of entities that eventually became encapsulated (Eigen & Schuster 1977). Nevertheless, the gulf between the pre-biotic chemistry and the simplest life forms is still huge and any number of explanations only account for a tiny portion of the conceptual distance.

Another approach, “Top-Down,” uses current taxa to infer the nature and timing of the origin of life on Earth. To do so, we take current examples of life on Earth and trace their ancestry, by comparing the nearly hundred shared genes, primarily associated with biological translation (Koonin 2011). All life shares a last universal common ancestor, “LUCA” for short. There may have been several origins of life, but our evidence is insufficient to distinguish this scenario from a single origin. Nevertheless, at least one origin, presumably in Earthly pre-biotic conditions, led to the existence of LUCA, an important constraint upon theorizing about the origin of life. It is widely expected that LUCA was merely one creature in a larger population and existed long after the origin of the first organism. There are also a variety of concerns with respect to LUCA: whether it was simple or complex (Mariscal & Doolittle 2015); whether it had a membrane that resembled any of the current membranes (Koonin 2011); whether the genes it contained were ancestors of our own genes or subsequently acquired (Doolittle & Brown 1994, Woese & Fox 1977; Woese 1998); whether its genome was made of DNA (Forterre 2006a), whether it was a heterotroph or autotroph; where it lived; and when it lived.

The gap between Top-Down and Bottom-Up approaches is huge: untold generations passed between pre-biotic chemistry and LUCA. We may never be able to solve Life’s origin, but each step brings us closer to understanding the trajectory.

Even the most pessimistic analyses of the likelihood of life suggests life on Earth is not unique (Frank & Sullivan 2016). Many scientists take that as a good reason to search for life elsewhere in the Universe. The current search for life elsewhere focuses on two extremes: the chemical byproducts of life and the technological signals of intelligent life. The social interactions of alien populations might be interesting, but they are hard to study as of yet. Thus, we search for biosignatures that might uniquely identify life from a great distance. We’ll take each in turn.

Biosignatures, as the name implies, are purported to be markers of life. Chemical biosignatures are compounds either rarely or never produced without the assistance of life on Earth. Finding biosignatures thus implies a material conception of life, likely in the form of biochemistry, metabolism, or thermodynamics. There have been many attempts to detect biosignatures, primarily on Mars. These approaches include experiments done on planetary surfaces, observations from Earth or low-earth orbit, and study of meteors and other debris from nearby planetary bodies.

More practically, satellite or telescope observations of other planets have been used to search for gasses outside of thermodynamic equilibrium. Methane has been sporadically detected on Mars since 2004 (Formisano et al. 2004, Webster et al. 2018) with an accompanying claim of formaldehyde detection (Peplow 2005). Venus has also been a source of attention, with phosphine gas detected in the clouds above Venus (Greaves et al. 2020). A controversial finding, it nevertheless caught the scientific imagination. Future scientific research is expected to accelerate this method of observation, especially with new data gathered by the new James Webb Space Telescope (JWST). With its equipment, JWST is able to image exoplanets at resolutions allowing the detection of gas biomarkers in the atmospheres of exoplanets (Loeb & Maoz 2013).

By contrast, there have been scarce attempts to detect chemical life while on the surface of another planet. In 1975, NASA sent the Viking landers to Mars, tasked with a variety of scientific experiments including some that were purported to detect life if it was present. One, the Labeled Release Experiment, did, but its results were inconsistent with the other on-board experiments, so the result was deemed inconclusive (Levin & Straat 1976, Ezell & Ezell 1984). The current Perseverence rover on Mars is able to assess certain biosignatures and upcoming missions by NASA, the Chinese National Space Administration, and the Japanese Aerospace Exploration Agency all seek to determine whether Mars has evidence of past or current life.

It is not obvious that life on Mars would be a separate origin than life on Earth, as the two planets exchange tons of rocks each year and it is at least theoretically possible that life could have formed on one planet and been subsequently transferred to the other (McKay 2010). Since Mars is a smaller body than Earth, it coalesced before Earth and thus it is conceivable that life might have formed there first, although this is a relatively marginal view in the astrobiology community. Meteorites from Mars and other planetary bodies have also been the source of purported biosignatures. The Martian meteorite ALH84001 was instrumental in forming the science of astrobiology in 1996, after NASA scientists discovered bacteria-like structures (McKay et al. 1996). Subsequent meteorites have also garnered scientific interest (e.g. White et al. 2014).

The other major attempt to search for life, that of searching for intelligence, more readily captures the imagination. The search for extraterrestrial intelligence (SETI) has been ongoing for centuries (Dick 1982). Fierce debates between those that took Earth to be unique and those that took it to be one of a plurality of worlds persisted for millennia (and still do, to some extent). Advocates of the plurality of worlds view searched their telescopes for evidence. A famous instance is Percival Lowell’s drawings of Martian canals in the 1890s. Influenced by the mid-1800s observations of what appeared to be channels criss-crossing Mars, Lowell drew a series of canals based on his observations. Science fiction soon picked up the observation and conjectured a dying civilization, hoping to squeeze water out of the last bits of remaining ice in the Martian poles.

Partially driven by the science fiction following Lowell’s drawings, the early 20th century saw increased interest in detecting radio signals from Outer Space. This interest accelerated after the launch of Sputnik in 1957 and was more systematically and formally approached starting in the late 1970s. SETI research has not been publicly funded since 1994, but private and public donors, as well as academic and lay researchers have kept the program going since. There are many technical challenges to the search: space is unimaginably huge, signals are weak, possibilities of interstellar communication are myriad, and our searches can only cover an insignificant portion of the task.

More controversially, many dozens of messages have been sent into Outer Space since 1974. A few have been in the form of physical objects aboard spacecraft, but most have been radio signals aimed at promising stars or star clusters. sometimes called Active SETI or METI (Messaging Extraterrestrial Intelligence). Although the practice continues due to its low cost and relative ease, many philosophers, scientists, and policy experts have come out against the practice largely due to the risk of broadcasting our presence to potentially hostile forces on behalf of future generations that cannot consent (Smith 2020).

Scientists grow more concerned about philosophical questions when scientific limitations or conceptual choices are made apparent to them. Those scientists who study deep time, deep space, abstract issues, or questions of ethics are often keenly aware of the philosophical choices that influence their research from identification of research question to interpretation of the data. This section briefly goes through other scientific contexts in which how life is defined is relevant, which address scales well below and well above the organism level.

There are several biological entities for which it is an open question as to whether they are alive. Viruses, for example, are units of genetic material encased in a protein coat. It is unknown whether all viruses share common ancestor (Koonin et al. 2006, Moreira and López Garcia 2009) nor how they originated, be it escaped transposable elements, reduced cells, or some ancestral third option (Forterre 2006b). The status of viruses as living is mired with controversy, with some people holding virons to be alive, others believing them not to be, and a third camp has them as living only in the context of an infected cell, but a mere ‘seed’ otherwise (Forterre 2010).

There are other entities in the “twilight zone of microbiology,” including transposable elements, viroids, unculturable (but putatively existing) microbes, organisms in vegetative states, and prions (Postgate 1999). The problems facing each of these are similar: several of them can evolve by natural selection, are biochemically complex, but lack other properties associated with life. For example, prions are protein products of life that can fold other prions in a way that allows for cumulative evolution (Li et al. 2010). They are rarely included in the category ‘life’ due to their inactivity in most settings and rather simple origin as a misfold of a functional protein.

If there is a twilight zone of microbiology, there is also a twilight zone of ecology. Organisms form populations, species, lineages, clades, and ecosystems. The status of each of these is an open question, but they have many of the same features associated with life as described above. Perhaps the strongest case can be made for eusocial insects, such as some ants, bees, wasps, and termites. In several species, there are rigid distinctions between the castes that reproduce and those that do not, with many of the latter serving the role of caring for the young (Hölldobler & Wilson 2009). One might note that entities above the organism level are as a rule less integrated and connected than the organisms that comprise them. This is perhaps a general feature of life: from the perspective of every item in the biological hierarchy, its parts are much more homogenous than it is. Our cells seem much more integrated and self-contained than our bodies, so, too, are individual insects more self-contained than the colonies to which they belong.

Most controversial has been the case of Gaia. Gaia is a term from Greek mythology; she is a personification of the planet Earth. In 1979, James Lovelock, revived the concept in his book, Gaia: A New Look at Life on Earth . In his view, the Earth-wide set of interlocking ecosystems could be viewed as a single entity. One insight of Lovelock’s was already mentioned in the previous section: planet-wide interactions are the scale that matters in detecting life elsewhere. Lovelock’s book sparked controversy centered around the plausibility of his model of the Earth as a self-regulating homeostatic system. In the view of many at the time, it was an inaccurate description: Earth could not evolve in principle, and the subsequent ontological move of granting Earth the status of life was unmotivated (Doolittle 1981). Recent attempts to revitalize the notion of Gaia on a more theoretic footing involve both abiotic and biotic regulatory mechanisms and natural selection acting at the level of clades (Lenton et al. 2018, Doolittle 2019). Regardless of current attempts at a theoretical justification, the thought of Earth as a living entity motivated many in the environmental movement and the idea remains a common reference.

The term ‘life’ is important outside of biology. Often, the focus is not on the concept of life or life in general, but on the status of individual living entities. Typically, the focus is on the beginning and end stages of individual lives, which raises legal, religious, and moral questions. The start of an individual life has been the source of contraception and abortion discussions (Noonan 1967, Dellapenna 1978). Unfortunately, developmental biology does not provide an uncontroversial starting point for when ‘life’ begins (Maienschein 2014). The end of individual lives was also a heated debate in the 20th century as new technologies were able to keep human bodies alive long after they would have died in nature (DeGrazia 2016).

Any discussion of defining life in these contexts should begin by distinguishing between life and other phenomena that are often conflated with it in public discourse, such as sentience, personhood, and moral considerability. It’s unclear how much ontological, epistemic, or moral weight the category of life has independently of other properties. Attributing moral worth to non-living entities is still a minority position in environmental or comparative philosophy (but see Leopold 1949, Basl 2019). Thus, a starting position might be that life is a prerequisite for moral considerability. Nonetheless, most humans don’t mind killing bacteria for the sake of cleanliness and many people eat or wear the flesh of animals. So, in many discussions, life is only valuable when it is the vehicle for other equally nebulous properties like sentience, personhood, or immaterial souls.

If any living entities have a distinct moral or ontological status, most philosophers would accept that humans are among them (Rolston 1975, Goodpaster 1978). In these contexts, it matters when individual humans come into being and acquire such a status in their own right, be it conception, birth, or some time period in between. Considered opinions differ as to when this occurs and in virtue of what, be it mere possibility of self-sustained life, sentience, or other features. There is still a rampant pro-life/pro-choice split in cultural politics, which is somewhat lessened in European countries (Corbella 2020). There are equivalent, but less tendentious analogues in the contexts of euthanasia, the death penalty, war, and the prevention of death and disease. In these debates, both ethical and metaphysical commitments matter.

The public questions of life are often raised by new technologies. In the abortion discussion above, for example, new techniques to end pregnancies, from birth control to abortion procedures, as well as new medical technologies facilitating premature deliveries made the topic more contentious. Other technological innovations also raise questions about life. One such area is that of transhumanism (c.f. More and Vita-More 2013). Transhumanism is the movement aimed toward the use of technology for the human enhancement of social, psychological, and physical lives. These can range from prosthetics to implants or from pharmaceuticals to mental ‘uploading.’ There are bioconservatives, who argue against transhumanism for practical, moral, or aesthetic reasons. There are also posthumanists, who look forward to a world in which humans are replaced or eliminated by subsequent artificial intelligence. The debate over whether such posthumans might be ‘alive’ is similar in structure to the artificial life discussion in section 3. Bioconservatives also argue against this view. Among the topics in these debates are whether a particular technology counts as therapy or enhancement, whether the risks of alteration outweigh the benefits, whether certain goals of transhumanism are even possible, and which alterations will affect the moral or ontological status of the people that receive them.

That life is a source of ethical, legal, and political controversy is to be expected. And although it is beyond the scope of this article to adjudicate these debates, advocates ought to be aware of the deep vagueness in biology and disagreement within philosophy with respect to what life is, what an individual living organism is, when individual lives begin or end, and what features of life ground moral considerability.

Although the conceptual terrain of life concepts is well covered, there is no accepted view as yet. This is unlikely to change given the disciplinary backgrounds, explanatory values, and theoretical commitments of the stakeholders involved. A wide range of practices rely on competing conceptions of life: including artificial life, origins-of-life research, the search for life, and other projects described above.

Future scientific discoveries or inventions may break this impasse, as they have in other cases of theoretical gridlock. The development of atomic theory, discussed in section 2, created new categorical divisions that scientists accepted as more real than the categories of the ancients or alchemists. With this conceptual fragmentation, old categories were discarded and new ones accepted. One can imagine something similar happening in the case of life: many discoveries might show a clear cluster of how complex, lifelike entities can form from prebiotic chemistry, eventually winning over the majority of the scientific and philosophical community (e.g. Weber 2007, 2010).

Conversely, a simple decision might be made based on shared values or explanatory goals. The example of death may be illustrative. After decades of debate, a new decision, not a discovery, was made. Physicians concluded the irreversibility of death was the most important property for their purposes. They adopted the concept of whole-brain death as their operational criterion (DeGrazia 2016). The facts on the ground did not change, but the shared understanding did.

Finally, perhaps life will be accepted as a polysemous concept with each definitional cluster applying to a subset of the whole: biochemical life, evolutionary life, metabolic life, etc. Researchers may rely on context, accept some miscommunication, or simply stipulate the kind of life they mean. The example of planets, discussed in Brusse 2016 may help make this point. There was always a huge diversity within the category planet, which included the Sun and Moon until the Renaissance. In the early 1800s, asteroids were discovered. Initially, they were considered planets, they were demoted to ‘minor’ planets a few decades later, then simply ‘asteroids’ after the 1950s. Pluto was discovered in 1930, recognized as the smallest planet by the 1970s. From 1992 until 2006, many objects similar to Pluto were discovered until astronomers decided that the term planet actually covered at least two distinct, but scientifically interesting categories: typical planets and dwarf planets. Similarly, perhaps some of the categories described in section 1.2 will form the basis of accepted sub-categories of life.

It is still an open question as to how long the current situation will persist before a discovery forces a scientific reckoning or a decision obviates the need. For now, the debate continues.

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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.

Weber, Bruce, “Life”, Stanford Encyclopedia of Philosophy (Fall 2021 Edition), Edward N. Zalta (ed.), URL = < https://plato.stanford.edu/archives/fall2021/entries/life/ >. [This was the previous entry on this topic in the Stanford Encyclopedia of Philosophy — see the version history .]
Darwin, C., Letter to J. D. Hooker, 01 February 1871 , Letter no. 7471, Darwin Correspondence Project.

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Philosophy
philosophy, (from Greek, by way of Latin, philosophia, "love of wisdom") the rational, abstract, and methodical consideration of reality as a whole or of fundamental dimensions of human existence and experience. Philosophical inquiry is a central element in the intellectual history of many civilizations. The subject of philosophy is treated ...
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1.1: What is Philosophy?
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philosophy: [noun] all learning exclusive of technical precepts and practical arts. the sciences and liberal arts exclusive of medicine, law, and theology. the 4-year college course of a major seminary. physical science. ethics. a discipline comprising as its core logic, aesthetics, ethics, metaphysics, and epistemology.
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an overall vision of or attitude toward life and the purpose of life; any of various philosophies that emphasize human life or life in general… See the full definition Menu Toggle
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Life
Similarly, for any definition of life, one can either show living cases that are left out of the definition or non-living cases that are included by it. Life is organized, but so are geological formations. Life processes energy, but so does fire. Life evolves using complex biochemistry, but so do prions.