History of philosophy

• 1. Introduction

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  The history of philosophy is the systematic study of how philosophical thought developed. It centers on philosophy as rational inquiry built on argumentation. Yet some theorists widen the frame to take in myth, religious traditions, and proverbial lore.

  In the 6th century BCE, in Ancient Greece, someone asked what the cosmos was fundamentally made of. That question opened a span of more than 2,500 years that continues to evolve today. From it grew inquiries into the nature of reality and the mind, into how people should act, and into how anyone arrives at knowledge.

  But the Greek thread is only one strand. Arabic-Persian philosophy reached its peak during the Islamic Golden Age. Indian philosophy traced its roots to scriptures called the Vedas. Chinese philosophy asked about right social conduct, government, and self-cultivation. Why do some thinkers treat the history of philosophy as part of philosophy itself, and others as mere intellectual history? Who decided that a butcher cutting an ox could illustrate a way of living? And how did a method of doubt, a razor, and a boundless substance each reshape what people believed was true?

• 2. A History Or A Philosophy

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  The history of philosophy is not merely a collection of theories. It attempts to show how these theories are interconnected. Some schools build on earlier theories. Others reject them and offer alternative explanations. The field aims for a systematic and chronological exposition of concepts, doctrines, the philosophers who conceived them, and the schools to which they belonged.

  Purely mystical and religious traditions are often excluded if their claims are not grounded in rational inquiry and argumentation. Some theorists, though, treat the topic broadly. They include the philosophical aspects of traditional worldviews, religious myths, and proverbial lore.

  Two components pull against each other inside the discipline. The historical component asks which philosophers held which views, and how their social and cultural contexts shaped them. The philosophical component evaluates those theories for truth and validity, weighing their arguments and exposing their hidden assumptions.

  Neo-Kantians like Wilhelm Windelband argued that philosophy is essentially historical. On their view, you cannot understand a philosophical position without understanding how it emerged. That stance makes the history of philosophy controversial as a discipline distinct from philosophy itself. Closely related is the historiography of philosophy, which examines the methods historians use and tracks how dominant opinions in the field have changed over time.

• 3. The Boundless And The Forms

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  Thales, who lived around 624 to 545 BCE, is often regarded as the first philosopher. He tried to describe the cosmos through a single first principle, an arche, and identified water as the primal source of all things. This was the opening move of Presocratic philosophy, which lasted until about the mid-4th century BCE and survives today only in fragments reconstructed from later quotations.

  Anaximander, roughly 610 to 545 BCE, reached for something more abstract. He called the eternal source the apeiron, meaning the boundless, and placed it beyond human perception. Heraclitus, about 540 to 480 BCE, saw the world in constant flux and said one cannot step into the same river twice. Parmenides, around 515 to 450 BCE, insisted the opposite, that true reality is unchanging, eternal, and indivisible. His student Zeno of Elea built paradoxes like Achilles and the Tortoise to argue that motion and change are illusions.

  Socrates, 469 to 399 BCE, wrote nothing himself. His influence came through the Socratic dialogue, which begins with simple questions and critically reflects on the assumptions beneath them. He cared less about metaphysics and more about what it means to lead a good life, examining justice, courage, and wisdom. He advocated no specific doctrine. He wanted his audience to recognize their own ignorance.

  Plato, 427 to 347 BCE, recorded much of what we know about Socrates. His theory of forms held that true reality lies in abstract, eternal forms such as beauty, justice, and goodness. The physical world is an imperfect copy. Plato divided the soul into reason, spirit, and desire, and founded the Academy, often considered the first institution of higher education. Aristotle, 384 to 322 BCE, began there as a student. He accepted the distinction between form and matter but denied that forms exist independently of matter, a dispute that became the problem of universals and would occupy philosophers for centuries.

• 4. Faith Seeking Reason

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  The Christian Emperor Justinian ordered the closure of philosophical schools, including Plato's Academy, in 529 CE, seeking to suppress non-Christian teachings. Intellectual activity then concentrated within the Church, where diverging from doctrinal orthodoxy carried real risk. Some scholars have called this era a dark age. Its central questions were the problem of universals, the nature of God, proofs for God's existence, and the relationship between reason and faith.

  Augustine of Hippo, 354 to 430 CE, drew on Neoplatonism to interpret Christian doctrine. He confronted the problem of evil, asking how evil could exist in a world made by a benevolent, all-knowing, all-powerful God. His answer rested on free will, the human capacity to choose between good and evil and bear responsibility for it.

  Anselm of Canterbury, 1033 to 1109 CE, is often called the father of scholasticism. He treated reason and faith as complementary. His ontological argument defined God as the greatest conceivable being and reasoned that such a being must exist outside the mind, since real existence is greater than existence in thought alone.

  Thomas Aquinas, 1224 to 1274 CE, is often considered the most influential medieval philosopher. Rooted in Aristotelianism, he built a comprehensive scholastic system and compiled much of it in the Summa Theologiae. He held that reason supports Christian tenets but cannot reach all truths, so faith in revelation remains necessary. His Five Ways are five arguments for the existence of God. William of Ockham, 1285 to 1347 CE, one of the last scholastics, formulated Ockham's Razor, the principle that the simplest explanation, assuming the fewest entities, should be preferred.

• 5. Method And Doubt

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  Francis Bacon, 1561 to 1626 CE, wrote Novum Organum to replace Aristotle's treatises on logic. He emphasized inductive reasoning, deriving general laws from many individual observations, and stood as a transitional figure between the Renaissance and modernity. Galileo Galilei, 1564 to 1642 CE, advanced the Copernican Revolution by asserting that the Sun, not the Earth, sits at the center of the Solar System.

  René Descartes, 1596 to 1650, sought absolutely certain knowledge through methodological doubt, questioning every belief until he reached the statement I think, therefore I am. His system rests on substance dualism, the claim that mind and body are distinct, independent entities that coexist. Baruch Spinoza, 1632 to 1677, leaned harder on deductive reasoning with his geometrical method, starting from self-evident axioms, and arrived at monism, the view that only one substance exists in the universe.

  John Locke, 1632 to 1704, is often considered the father of empiricism. In An Essay Concerning Human Understanding he rejected innate knowledge and called the mind a blank slate at birth. George Berkeley, 1685 to 1753, pushed empiricism toward idealism, arguing that objects exist only insofar as they are perceived. David Hume, 1711 to 1776, went further still, holding that one cannot know with certainty that one event causes another, since the connection between cause and effect is never directly perceived.

  Immanuel Kant, 1724 to 1804, tried to synthesize empiricism and rationalism. His transcendental idealism described how the mind, through pre-established categories, shapes human experience. In ethics he built a deontological system around the categorical imperative, which defines universal moral duties. Thomas Hobbes, 1588 to 1679, in Leviathan, viewed the natural human state as a war of all against all, escaped only through a social contract in which individuals cede rights to a powerful central authority.

• 6. Systems And Their Critics

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  In the 19th century the term philosophy took on its modern meaning, a discipline distinct from the empirical sciences and mathematics. German idealism, inaugurated by Kant, sought a single unifying principle behind all reality. Johann Gottlieb Fichte, 1762 to 1814, located it in the activity of the transcendental ego. The philosophy of Georg Wilhelm Friedrich Hegel, 1770 to 1831, is often described as the culmination of this tradition, reconstructing history so that the measure of progress is the actualization of freedom.

  Karl Marx, 1818 to 1883, took inspiration from Hegel but rejected idealism for dialectical materialism, the claim that economics rather than spirit drives historical development. Arthur Schopenhauer, 1788 to 1860, influenced by Indian philosophy, held that the underlying principle of reality is the will, an irrational and blind force leading to suffering. He shaped Friedrich Nietzsche, who saw the will to power as a fundamental driving force in nature.

  Jeremy Bentham, 1748 to 1832, developed utilitarianism, judging actions by their utility, the pleasure and pain they produce, and aiming for the greatest good for the greatest number. His student John Stuart Mill, 1806 to 1873, refined this by arguing that the quality of pleasure matters, not only its quantity.

  Charles Sanders Peirce, 1839 to 1914, founded pragmatism in the United States, holding that the meaning of an idea lies in its practical, observable consequences. His lifelong friend William James, 1842 to 1910, applied these ideas to psychology and proposed the concept of a stream of consciousness, rejecting the notion that experiences are isolated events.

• 7. Clarity And Its Discontents

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  Twentieth-century philosophy is usually divided into two traditions. Analytic philosophy dominated English-speaking countries and prized clarity, formal logic, and linguistic analysis. Continental philosophy was more prominent in Germany and France, an umbrella term covering phenomenology, hermeneutics, existentialism, deconstruction, critical theory, and psychoanalytic theory. The century also saw an increased presence of female philosophers, though women remained underrepresented.

  Gottlob Frege, 1848 to 1925, pioneered modern symbolic logic and pursued logicism, the thesis that arithmetic can be reduced to logic. Bertrand Russell, 1872 to 1970, extended that project to geometry and analysis, though it required axioms beyond logic alone. His student Ludwig Wittgenstein, 1889 to 1951, argued in the Tractatus Logico-Philosophicus that the world is made of atomic facts, then later rejected this, holding instead that language consists of games whose meaning is determined by usage.

  Edmund Husserl, 1859 to 1938, founded phenomenology, aiming for a pure, unbiased description of experience by suspending all antecedent beliefs. His student Martin Heidegger, 1889 to 1976, turned this into fundamental ontology and explored anxiety and authenticity. These ideas influenced Jean-Paul Sartre, 1905 to 1980, who developed existentialism, the view that humans are fundamentally free and responsible, in a life that lacks a predetermined purpose.

  Michel Foucault, 1926 to 1984, argued that knowledge is always shaped by power. Jacques Derrida, 1930 to 2004, developed deconstruction to expose hidden contradictions within philosophical texts. The Frankfurt School produced Critical Theory, a social philosophy that sought not only to understand society but to liberate people from domination, with figures such as Theodor Adorno, 1903 to 1969, and Herbert Marcuse, 1898 to 1979.

• 8. Reason Revelation And The Way

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  Avicenna, 980 to 1037, built a comprehensive philosophical system meant to give a rational understanding of reality spanning science, religion, and mysticism. He distinguished contingent existence from necessary existence, placing God as the only necessary being on whom everything else depends. His system profoundly influenced both Islamic and Western philosophy. The classical period of Arabic-Persian philosophy began in the early 9th century CE, roughly 200 years after the death of Muhammad, and one of its key topics was how reason and revelation could both lead to truth.

  Al-Ghazali, 1058 to 1111, was highly critical of Avicenna's rationalism. In The Incoherence of the Philosophers he argued that many philosophical teachings were riddled with contradictions and incompatible with Islamic faith. He did not reject philosophy outright but believed it should be subordinate to mystical intuition. His skepticism about reason is often credited with the waning influence of philosophical inquiry that followed. Mulla Sadra, 1571 to 1636, later advanced a process philosophy emphasizing continuous change, and defended panpsychism, the claim that all entities possess consciousness to varying degrees.

  In India, the Upanishads introduced Atman, the eternal self, and Brahman, the ultimate reality, and asked how the two connect on the path to liberation. Adi Shankara, around 700 to 750 CE, advanced Advaita Vedanta, a radical monism holding that Atman and Brahman are identical and that the world's multiplicity is an illusion, or Maya. Buddhism, founded by Gautama Siddhartha, 563 to 483 BCE, denied any permanent self. Jainism, founded by Mahavira, 599 to 527 BCE, built itself on non-violence, non-absolutism, and asceticism.

  Confucius, 551 to 479 BCE, taught that a good life aligns with the Dao, understood as moral conduct, filial piety, and the family as the foundation of society. Laozi, of the 6th century BCE, founded Daoism and emphasized wu wei, effortless action in accordance with the Dao. Zhuangzi, 399 to 295 BCE, used parables to express his ideas, including a butcher who cut an ox effortlessly as his knife followed the optimal path. In his butterfly dream he wakes and questions whether he is a man who dreamt of being a butterfly, or a butterfly now dreaming he is a man.