History of Western Philosophy



The terms logic and reason are, in everyday usage, synonymous. To use logic/reason is to draw conclusions that make sense based on a given body of information. (Thus, terms like "logical analysis" and "rational inquiry" are also synonymous.) In the West, logic/reason was first explicitly identified and discussed by the ancient Greeks.

Throughout most of history, all logical analysis was referred to as "philosophy". Today, however, a distinction is usually drawn between philosophy and science. Philosophy encompasses matters for which objective evidence does not exist, while science covers matters for which it does. (Something is "objective" if it can be physically observed or measured.)


Philosophy may be defined as "the study of existence, knowledge, and values". The study of existence is often referred to as "metaphysics", while the study of knowledge is called "epistemology". The study of values can be divided into two main branches: morality ("ethics") and beauty ("aesthetics").

Common ground lies between philosophy and religion (belief in the supernatural). Both philosophers and theologians have asserted belief in supreme beings, and have attempted to describe the nature of these beings and their ethical desires. The distinction is that philosophical belief is based on logical argument, whereas religious belief is based on revelation (direct transmission of knowledge to humans from the supernatural, e.g. visions or scripture).

Why Study Philosophy?

Everyone is a philosopher to some extent, given that any examination of existence, knowledge, or values constitutes philosophy. In terms of exposure to the philosophical ideas of others, most people are content with the views they naturally encounter in everyday life (e.g. conversing with family and friends, watching movies and television). With such a rich pool of philosophical opinions, there is arguably no need to consult works of "pure philosophy".

Indeed, philosophy is often perceived as a difficult, confusing scholarly field of questionable value. This view is not surprising; unlike science, whose arguments only survive if supported by evidence, philosophical arguments cannot be tested. This allows various diseases of philosophy to persist indefinitely, the two most common of which may be ambiguity (which makes it impossible to garner consensus on the meaning of a philosophical argument; if, indeed, the author even had a clear meaning in mind) and intellectual hallucination (in which the author examines aspects of reality that simply don't exist).

There is no need for the amateur scholar to become lodged in such quagmires, however; Essential Humanities merely prescribes familiarity with the broad course of philosophical thought, along with some basic terminology. Though present-day philosophers work largely in ivory-tower isolation, the historical impact of philosophy is wide-ranging, from science, to government, to religion, to the general outlook and values of societies. And though one might not feel the need to consult philosophers regarding one's beliefs about the "big questions", it can be rewarding to know essentially how these questions have been approached through the ages.

Table Summary

Summary of Western Philosophy
general philosophy political philosophy
Archaic outward philosophy (Thales)
inward philosophy (Parmenides)
Classical Socrates (persistent critical reflection)
Plato (theory of forms)
Aristotle (four causes)
Plato (philosopher kings)
Aristotle (three forms of government)
medieval Christian philosophy: Platonic (Augustine) > Aristotelian (Aquinas) Christian political theory
Reformation Descartes (I think, therefore I am) Machiavelli (political realism)
Enlightenment Kant (experience shaped by mind) social contract: Hobbes, Locke (liberalism), Rousseau
modern transcendentalism, existentialism Mill (utilitarianism, positive liberalism)

Main Article


All Western philosophers prior to Socrates are known as the "presocratics".

Western philosophy was born during the Archaic age of Greece (ca. 800-500 BC), when Greek thinkers broke with purely mythological explanations of the world by attempting to explain nature logically. Apparently the first to do so was Thales (the "father of Western philosophy"), who initiated a search for the fundamental substance of all matter (see History of Science). Thus did Western philosophy begin with the field of science (aka "natural philosophy").

To be geographically specific, Western philosophy was born in Miletus, a large Greek city on the west coast of Asia Minor (now Turkey). This ancient city gave rise to the earliest Greek philosophers, namely Thales and his successors (most famously Anaximander and Anaximenes). From Miletus, philosophy spread rapidly across the ancient Greek world.

Apart from Thales, the most revolutionary presocratic philosopher was Parmenides, the first major practitioner of "inward philosophy"; that is, philosophy that examines the mind itself (as opposed to the "outward philosophy" of the natural sciences). He argued, like so many philosophers since, that we cannot trust our sensory perceptions to accurately inform us of reality; dreams and hallucinations, for instance, illustrate how misleading our senses can be. Parmenides was consequently the first to articulate the position of rationalism, which asserts that knowledge of reality arises (solely or principally) from rational analysis of innate knowledge (as opposed to analysis of sensory experience). Most famously, he argued that there is no change of any kind in the world, despite the constant change we seem to see everywhere.

The opposite position to rationalism, which argues that knowledge of reality is obtained (solely or principally) via analysis of sensory data, is known as empiricism. Thales and his successors were thus the first empiricists.


The Classical age of Greece (ca. 500-330 BC) featured the three most influential Western philosophers of all time: Socrates, Plato (a student of Socrates), and Aristotle (a student of Plato). Socrates and Plato were both Athenian, while Aristotle moved to Athens for a time to study at the Academy. (The Academy, Plato's school of philosophy, became the most influential ancient model for Western educational institutions.)

Socrates is remembered primarily for his tireless campaign that philosophers should constantly reexamine their beliefs, in order to clarify vague arguments and purge logical inconsistencies. This notion of persistent critical reflection constitutes his outstanding contribution to Western thought. The importance of Socrates' message, though it seems obvious today, is difficult to overestimate; some even regard him the most important thinker of all time. At any rate, Socrates' efforts introduced an unprecedented level of rigour and precision to Greek philosophy (though truly relentless critical reflection would not take hold across the West until the Enlightenment).45

According to Socrates, the duty of a philosopher is chiefly to assist others in discovering truth for themselves, rather than communicating truth directly. He achieved this primarily via the Socratic method, which he is credited with innovating. Instead of offering one's knowledge or opinions on a given issue, the socratic method consists simply of asking probing questions about the issue. Over time, this approach leads the person responding to the questions to see new aspects of the issue, to sharpen their terminology, and to rectify their position if inconsistencies are detected.2,6


Socrates' greatest successor was Plato. The views of these two thinkers are sometimes difficult to separate, given that the words of Socrates (who wrote nothing himself) are preserved chiefly in the works of Plato. Throughout these works, it is often unclear whether Plato is putting forward his own ideas or those of his teacher. In a sense, Plato's writings are jointly authored by both men.

Most of Plato's work is written in the form of dialogue (aka dialectic), in which an issue is explored via discussion between two philosophers. Typically, one philosopher questions the other until a contradiction is revealed in their reasoning, thus discrediting their argument; Plato usually casts Socrates as the philosopher who conducts the questioning. (As noted above, this technique is known as the "Socratic method").

At the core of Plato's philosophy is the theory of forms, which asserts that every physical thing is merely an approximation of an eternal, non-physical "form". Although this theory (which Plato inherited from Socrates) may sound odd today (given our modern scientific perspective), it proved massively influential throughout the history of Western thought.

As an illustration, suppose that ten chefs enter a pizza competition in which each must adhere strictly to the same recipe. The resulting pizzas will be very similar in terms of appearance and taste, yet will nonetheless vary slightly. The recipe itself may be thought of as the "form" of a pizza: it is an exact concept of what a pizza should be. Actual, physical pizzas are mere approximations of this ideal form. Physical pizzas come and go, but the ideal pizza form is eternal and unchanging.

According to the theory of forms, this applies to all worldly phenomena. Though there are many trees in the world (each one unique), they are all approximations of the "ideal tree" form, which is an eternal, inherent part of the universe. Even concepts like beauty and justice are eternal forms; the extent to which a work of art is beautiful, or a human deed is just, is explained by the extent to which they mimic these forms. According to Plato, one only comes to fully understand the universe when one sees beyond transient earthly phenomena to their eternal underlying forms.2,18

Plato did not limit himself to lofty, abstract metaphysics, however. His most revered work, the Republic, is the founding document of Western political thought. It provides a detailed proposal for an ideally governed society, which features the absolute rule of its wisest members ("philosopher kings").2

Socrates was executed by Athens on grounds of heresy and corrupting youth. The eloquent self-defense he put forward at his trial is captured in the Apology, Plato's other most famous work (though the extent to which the Apology captures Socrates' precise words is unknown). (The term "apology" in this sense denotes a defense or justification.)


Socrates and Plato tended to analyze the world in a rationalist manner; that is, by examining philosophical matters (existence, knowledge, and values) via analysis of truths innately known by the mind, without reference to physical experience. (These two philosophers argued that the "forms" described above are present in the mind from birth, and therefore do not require physical experience to understand.) Aristotle, on the other hand, favoured an empirical approach, basing his philosophical system firmly on information received by the senses.

Aristotle saw no need for Plato's theory of forms, arguing that physical things simply exist; they are not approximations of abstract ideals. This is the fundamental contrast between the two most renowned figures in Western philosophy. Whereas Plato argued that true understanding of the universe is achieved by comprehending its eternal "forms", Aristotle stressed meticulous physical observation. Aristotle's approach is thus similar to the modern scientific outlook. (Aristotle did accept the existence of one non-physical thing, the "prime mover", to explain how the universe came into being in the first place.)4

The most famous concept within Aristotle's philosophy may be the four causes. (In this context, "cause" means "aspect".) As noted above, Aristotle argued that understanding of the universe is rooted in careful observation. The "four causes" are the four observable aspects of any particular thing. To be specific, the four causes of a thing are the material it is made of, the form the material takes, the cause of the thing coming into being, and the purpose of the thing.17

Aristotle's "Four Causes"
(material cause)
(formal cause)
(efficient cause)
(final cause)
horse flesh, bone, etc. horse parents mating to grow and thrive
chair wood chair carpenter to be sat upon

Modern science continues to investigate the universe in terms of material, formal, and efficient causes. While final causes are not relevant to physics or chemistry, they are still found in biology (e.g. the purpose of an organ).

In the realm of political philosophy, Aristotle argued in favour of democracy, albeit with limited suffrage (compared to modern democracies).2 His Politics (Aristotle's chief work of political thought, and one of the two foremost ancient works of political philosophy, along with Plato's Republic) famously identifies three basic types of government: rule by one (monarchy/tyranny), rule by a few (aristocracy/oligarchy), and rule by many (polity/democracy).8

Though no subsequent ancient philosopher would approach the influence of Socrates, Plato, or Aristotle, many schools of thought emerged throughout the remainder of antiquity (e.g. stoicism, which advocates strict control of one's emotions, and epicureanism, which argues that happiness is attained through a life of moderation). Meanwhile, with the rapid expansion of Christianity after 313 (when Constantine granted the religion official tolerance), theologians began to assemble a comprehensive Christian view of the universe by blending the revelations of scripture with Greek and Roman philosophy; until the High Middle Ages, their preferred philosophical source was Plato. These early Christian thinkers included Saint Augustine, one of the two most influential theologians in Western history (along with Thomas Aquinas).2,15

Middle Ages

ca. 500-1500

Much classical thought (including most of Aristotle) was lost in medieval Europe, surviving only among the Arabs. Beginning in the High Middle Ages, these writings were reabsorbed from the Islamic world.2 The prevailing Western philosophy of the later Middle Ages was scholasticism, which merges Christian theology with the work of Aristotle. The most influential scholastic was Thomas Aquinas, whose works (which provide a comprehensive account of all existence, including several logical proofs of God) helped reawaken European insterest in Aristotle, and have ever since comprised the foundation of Roman Catholic doctrine.1


ca. 1500-1650

The rejection of scripture as the foundation of philosophy marks the birth of modern philosophy. The leading figure in making this rejection was René Descartes, the "father of modern philosophy". Descartes was a staunch rationalist; that is, he believed that knowledge of reality could only be attained through reasoned analysis of innate knowledge (i.e. knowledge that a mind naturally contains from birth), as opposed to analysis of sensory experience. Descartes also argued in favour of mind-body dualism, the view that the mind has an existence beyond the physical, and can therefore outlive the body. (Dualism is yet another philosophical notion whose roots lie in ancient Greece.)1

Descartes' most famous argument states that while one cannot ever be certain that one is in the real, physical world (since there is always the possibility that one is dreaming), one at least knows with certainty that one exists, simply because one is thinking about it. He pithily stated this argument as "cogito, ergo sum" ("I think, therefore I am").2

Thought can be divided into two kinds: concrete, which concerns specific physical things, and abstract, which concerns non-physical things (i.e. ideas or qualities). To think about a specific green tree is to think concretely; the concepts of "tree" and "green", on the other hand, are abstractions. While the natural sciences examine the concrete world and discover abstract laws that govern its behaviour, the field of mathematics is purely abstract. Consequently, many philosophers who tend toward rationalism (including Plato) have been passionate mathematicians, as part of their efforts to understand reality. Descartes was no exception to this rule; most famously, he developed the Cartesian coordinate system, which united algebra and geometry.

Medieval political theory, which was founded (like medieval philosophy in general) on scripture, focused largely on determining ideal Christian political arrangements. Modern political philosophy emerged when thinkers set aside scripture and analyzed politics in an immediate, practical, realistic fashion. The primary figure in this transition was Niccolo Machiavelli, the "father of modern political thought". Machiavelli described how a ruler may exploit human selfishness and cruelty, expanding and maintaining power via ruthless manipulation.8,11,20


ca. 1650-1800

The most influential Enlightenment philosopher (upon the field of philosophy in general) was Immanuel Kant, who effected a revolution in Western philosophy by arguing that our perception of the physical world is shaped by our minds.44 Just as the structure of our eyes determines how we see things (e.g. the wavelengths of light we can see), so does the structure of our brains determine how we experience the physical world.

According to Kant, the human mind is structured according to innate "categories", which it imposes on the physical world in order to make sense of it.44 For instance, one of these categories is "causality". If one kicks a ball and sends it flying, one perceives via sensory experience that one's foot struck the ball, and that the ball flew through the air; only the presence of the causality category in the brain, however, makes one interpret the kick as having caused the ball's flight.

Apart from the notion of the mind "shaping" reality, Kant is known as the most famous advocate of deontological ethics, which assert that actions are inherently right or wrong; this position stands in opposition to consequentialism, which argues that the morality of an action depends on the results. In order to determine whether an action is morally right, Kant proposed a rule called the categorical imperative, which essentially states that an action is right for an individual provided that it would be right if everyone took that action.

The Enlightenment also gave rise to social contract theory and liberalism, arguably the two most important ideas in the history of political philosophy.

Social contract theory provides a criterion by which to judge whether or not a government is legitimate. First, one must imagine how humans behaved prior to the formation of government (when people lived in a "state of nature"). While these humans had no restrictions on their behaviour, they lacked protection against the harmful behaviour of others. This compelled them to come together and form a "social contract", whereby they accepted the authority of a government in exchange for its protection.

Although this thought experiment does not describe how governments have actually developed, it can be used to judge whether or not a government is legitimate. All one need do is specify the contents of the social contract: what authority does a government rightly hold, and what must it offer in return? A government that fails to abide by the contract can be declared invalid, and be legitimately overthrown by its people. Social contract theory thus rejects the notion of a "divine right" to rule, under which citizens have no right to protest or revolt.27

Thomas Hobbes, the founder of social contract theory, contended that humans are inherently selfish and cruel, which made life in the state of nature "nasty, brutish, and short".23 In the resulting social contract, people agree to be ruled by an absolutist monarch in exchange for protection from one another (since only a dictator is capable of restraining such violent creatures).25 The sole duty of the monarch is to protect people from physical harm; therefore the only just cause for rebellion is the monarch's failure to provide this protection.40

John Locke, the second great social contract theorist, argued that the state of nature was generally peaceful and tolerant; government was only rendered necessary by a minority of troublemakers.24 Locke was the first thinker to clearly articulate the position of liberalism, which argues that the overarching duty of government is to ensure individual freedom.28 This includes both freedom from harm (e.g. assault, theft, arbitrary imprisonment) as well as freedom of choice (e.g. speech, belief, economic activity). Locke argued that these freedoms are inherent "natural rights".

Hobbes and Locke both lived through the English Revolution, the most critical event in the long struggle between Parliament and the monarchy for governing authority. Though national representative assemblies had emerged in various Western nations, only England's managed to achieve major political power; perhaps it was this unique perspective that allowed the notion of liberalism to emerge and thrive. Up until the rise of liberalism, states across the world had generally emphasized the collective over the individual, repressing freedom in favour of unity, stability, and security.

Modern Western governments are liberal democracies; that is, democracies that embrace the philosophy of liberalism. Liberalism is thus one of the two pillars of modern Western government (along with democracy; see History of Democracy). The instrument through which liberalism (and democracy, for that matter) is realized is law, which furnishes citizens with freedoms and protects those freedoms from being violated by others (including the government itself). (A country features "rule of law" if it has a strong legal system to which all are subject, including the government; the alternative is "rule of man", in which government power is unrestricted.)

As the "father of liberalism", Locke may be the most influential of all political philosophers. His work (in particular the Second Treatise of Government) was widely embraced by political revolutionaries of the age (including those of England, France, and the United States), and lies at the roots of all modern-day liberal democracies.46,47 (Note that the concept of liberalism described here is distinct from "liberal" as in "left-wing". Most political parties in modern democracies, whether left- or right-leaning, are supporters of liberalism; they simply differ in their interpretations and policies.)

The third great social contract theorist was Jean-Jacques Rousseau, a supporter of liberalism who envisioned an idyllic state of nature. Rousseau argued that in nature, people do not behave immorally; only within the confines of a state that they become violent and oppressive, due to the false goals society convinces them to strive for (e.g. power, wealth, fame) in order to feel superior to others. In a state of nature, humans live as isolated individuals or families, and thus have no conception of these empty pursuits, nor neighbours of whom to become jealous.9,38

Since a social contract is an agreement to live in a society, it actually ends up robbing individuals of their natural freedom; hence Rousseau's most famous quote, "man is born free, and everywhere he is in chains". Rather than advocating a return to the state of nature, however, Rousseau argued that government is capable of overcoming the corruptive nature of society, providing it is constantly subject to the "general will" (i.e. the general consensus of the citizenry).9 Thus, Rousseau would only be satisfied with direct democracy or extremely consultative representative democracy.

Apart from his political writings, Rousseau is known primarily for the works Emile (which describes a program of education, largely self-directed, intended to combat the corrupting influence of society) and Confessions (often considered the first true autobiography, in that it realistically accounts the events of Rousseau's life). Though a few autobiographies had been written earlier, most famously Saint Augustine's own Confessions (the very first autobiography), these were works of Christian devotion that focus mainly on the authors' spiritual experiences.


ca. 1800-present

In terms of general philosophy, the two most famous nineteenth-century schools may be existentialism and transcendentalism. Both were influenced by the Romantic movement, which emphasized subjective, individual experience and belief over objective reality and societal values.

Transcendentalism stresses the fundamental goodness of humanity and the constant presence of the divine in people and in nature; by listening to one's intuition/feelings, one can "tune in" to this divine harmony, allowing one to unlock the profound truths of life (despite the absence of objective evidence). Transcendentalists argued that one should prioritize personally-discovered truth over social conventions and demands. The two foremost names in transcendentalism are Emerson and Thoreau; the most influential work of the movement is Thoreau's Walden, his account of living for two years in a cabin by Walden Pond, Massachusetts.2,29,36

Existentialism is transcendentalism's pessimistic cousin. Existentialists agree that profound truths can be discovered via introspection, and that individual belief should trump societal values; the road to truth, however, is described as exceedingly painful and bewildering, giving rise to despair and alienation. One must battle these negative tendencies of the mind by actively constructing meaning for one's own life (i.e. forging one's purpose in life and one's personal code of morality). The foremost names in existentialist literature may be Kierkegaard, Sartre, and Camus.2

During the twentieth century, philosophy became increasingly fragmented into highly-specialized fields, each of which might be occupied by a mere handful of scholars.31 It seems that while the world of philosophy may be indefinitely explored, its issues will never be resolved by majority consensus (as in the world of science). This is explained by philosophy's lack of objective evidence: while scientific theories can be tested, philosophy consists of innumerable arguments that can never be proven or disproven (or even necessarily demonstrated to be meaningful).

Political philosophy of the nineteenth century was shaped by the unprecedented economic growth of the Industrial Revolution and the terrible working conditions that accompanied it.37 Some philosophers were optimistic that, given time (and perhaps government intervention), the blessings of capitalism would eventually be shared among all levels of society. Others, most famously Karl Marx, felt that capitalism was unfixable and should be overthrown (see Marxism).

The most influential liberal philosopher of the nineteenth century was likely John Stuart Mill, the foremost proponent of utilitarianism.25 According to the utilitarian view, the right decision in any given situation is the one that brings the most good ("utility") to the most people. Using this argument, Mill championed such causes as women's suffrage and an end to slavery.2,25 (Utilitarianism provides an alternative to the notion of freedoms as "natural rights", a popular view among liberal thinkers.)

In fact, Mill advocated a new type of liberalism: positive liberalism. Classical liberalism (the original kind) argues that government should provide freedoms. Positive liberalism goes a step further, arguing that government should also provide citizens with the opportunity to exercise their freedoms, by ensuring a minimum standard of welfare. This minimum standard can be divided into two parts. Individual welfare provision, known as a "social safety net", directly ensures the welfare of individual citizens (e.g. unemployment insurance, public health care). General welfare provision ensures the welfare of society as a whole (e.g. environmental regulation, subsidized infrastructure).

A nation that embraces positive liberalism is often called a "welfare state" or "social democracy". The development of welfare states occurred throughout the twentieth century, especially after World War II.25,28 Following the economic slowdown of the late 1970s, however, classical liberalism experienced a revival. From that time to the present, many public services of Western nations have been cited as unsustainable and/or inefficient, and have been downsized or eliminated.27 The debate continues today as to how "classical" or "positive" liberalism ought to be (or equivalently, how "hands off" or "interventionist" government ought to be regarding citizens' welfare).

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