Ancient · Milesian school
Thales
c. 624–c. 546 BCE
The first Greek thinker remembered for explaining nature without appealing to the will of the gods. He held that everything comes from water.
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Philosophers
Lives shaped by argument, doubt, conviction, exile, friendship, and the persistent demand to think more clearly.
Ancient · Milesian school
Anaximander
c. 610–c. 546 BCE
Younger contemporary of Thales who traced the world to something boundless rather than to any familiar substance, and drew one of the first maps of the inhabited earth.
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Ancient · Milesian school
Anaximenes
c. 586–c. 526 BCE
The third Milesian, who made air the origin and explained every change by one mechanism: thickening and thinning.
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Ancient · Pythagoreanism
Pythagoras
c. 570–c. 495 BCE
Samian who founded a community in southern Italy, taught that souls are reborn, and left a tradition that read the order of the world as number and harmony.
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Ancient · Ionian
Xenophanes
c. 570–c. 478 BCE
A travelling poet from Colophon who attacked the gods of Homer and Hesiod and argued that human knowledge falls short of certainty.
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Ancient · Ionian
Heraclitus
c. 540–c. 480 BCE
Ephesian who wrote in deliberate riddles, holding that the world is an ordered process of opposites governed by a logos most people fail to hear.
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Ancient · Eleatic school
Parmenides
c. 515–after 450 BCE
Wrote a philosophical poem arguing that what is cannot come to be or perish, and that reasoning, not the senses, settles what exists.
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Ancient · Atomism
Democritus
c. 460–c. 370 BCE
With his teacher Leucippus, explained the world as atoms moving in empty space, and wrote as much about cheerfulness and conduct as about physics.
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Ancient · Classical Greek
Socrates
c. 470–399 BCE
Athens’ relentless questioner made the examined life philosophy’s enduring vocation. He wrote nothing; his method survives through the dialogues of Plato and other contemporaries.
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Ancient · Platonism
Plato
c. 428–348 BCE
Founder of the Academy and author of philosophical dialogues on justice, knowledge, love, politics, and the nature of reality.
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Ancient · Aristotelianism
Aristotle
384–322 BCE
Plato’s student built an extraordinary system spanning logic, ethics, politics, biology, rhetoric, and metaphysics.
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Ancient · Epicureanism
Epicurus
341–270 BCE
In the Garden at Athens, Epicurus taught that tranquility grows from friendship, modest pleasure, and freedom from needless fear.
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Ancient · Stoicism
Zeno of Citium
c. 334–262 BCE
Founder of Stoicism, teaching in Athens’ Painted Stoa that flourishing means living consistently with nature and reason.
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Roman · Stoicism
Seneca
c. 4 BCE–65 CE
Roman statesman and moral essayist who examined anger, adversity, time, wealth, and the practice of philosophical friendship.
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Roman · Stoicism
Epictetus
c. 50–135 CE
Formerly enslaved teacher whose practical ethics distinguishes what belongs to our agency from what does not.
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Roman · Stoicism
Marcus Aurelius
121–180 CE
Roman emperor whose private philosophical exercises became an enduring manual of attention, duty, and impermanence.
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Late Antique · Christian Platonism
Augustine
354–430
A pivotal thinker on time, memory, evil, freedom, and grace at the meeting point of Platonism and Christianity.
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Medieval · Islamic philosophy
Al-Farabi
c. 870–950
Known in Arabic as the Second Teacher, after Aristotle. He gave Greek logic a home in Arabic and imagined a city governed by a philosopher who is also a prophet.
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Medieval · Islamic philosophy
Avicenna (Ibn Sina)
c. 980–1037
Drew the distinction between what a thing is and that it is, and built from it an argument for a necessary being that European theology was still using six hundred years later.
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Medieval · Islamic philosophy
Averroes (Ibn Rushd)
1126–1198
Spent his life explaining Aristotle line by line, and argued that the law does not merely permit philosophy but requires it of those able to do it.
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Medieval · Scholasticism
Thomas Aquinas
1225–1274
Synthesized Aristotelian philosophy with Christian theology through a systematic account of nature, reason, and law.
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Early Modern · Rationalism
René Descartes
1596–1650
Sought certainty through methodic doubt, transforming debates about knowledge, mind, and the foundations of science.
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Early Modern · Rationalism
Baruch Spinoza
1632–1677
Developed a geometric philosophy of one infinite substance, human emotion, freedom, and intellectual love.
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Enlightenment · Empiricism
John Locke
1632–1704
A foundational theorist of experience, personal identity, toleration, natural rights, and limited government.
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Enlightenment · Empiricism
David Hume
1711–1776
A radical empiricist and naturalist who challenged causation, the self, religious argument, and rationalist ethics.
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Enlightenment · Transcendental idealism
Immanuel Kant
1724–1804
Recast knowledge, ethics, and aesthetics by asking how the mind structures experience and how freedom grounds duty.
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Modern · German idealism
G. W. F. Hegel
1770–1831
Argued that thought, history and freedom develop through their own contradictions, and that what looks like a succession of dead systems is one argument working itself out.
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Modern · Pessimism
Arthur Schopenhauer
1788–1860
Interpreted reality as ceaseless striving while locating relief in art, compassion, and the quieting of desire.
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Modern · Existentialism
Søren Kierkegaard
1813–1855
Explored anxiety, faith, choice, and the irreducible inwardness of an individual life.
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Modern · Nihilism
Friedrich Nietzsche
1844–1900
Diagnosed inherited values and nihilism, asking how life might create values after the decline of metaphysical certainty.
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Modern · Marxism
Karl Marx
1818–1883
Analyzed capitalism through labor, class, alienation, and historical transformation.
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20th Century · Analytic philosophy
Ludwig Wittgenstein
1889–1951
Wrote one book that claimed to have solved philosophy's problems, spent the rest of his life dismantling it, and left the second book unpublished at his death.
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20th Century · Phenomenology
Martin Heidegger
1889–1976
Reopened the question of what it means to be at all, and compromised himself irreparably by joining the Nazi party as rector of Freiburg in 1933.
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20th Century · Existentialism
Jean-Paul Sartre
1905–1980
Argued that radical freedom and responsibility shape human existence in a world without predetermined essence.
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20th Century · Existentialism
Simone de Beauvoir
1908–1986
Connected existential freedom to embodiment, gender, oppression, ambiguity, and reciprocal recognition.
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20th Century · Absurdism
Albert Camus
1913–1960
Confronted the tension between our hunger for meaning and the world’s silence, answering it with lucidity and revolt.
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Ancient · Cynicism
Diogenes of Sinope
c. 412/404–323 BCE
The most famous Cynic made philosophy visible as a life of radical simplicity, shameless truth-telling, and contempt for empty convention.
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Early Modern · Social Contract
Thomas Hobbes
1588–1679
Hobbes rebuilt political authority from fear, equality, and consent, arguing that peace requires a common power strong enough to end private war.
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Renaissance · Political Realism
Niccolò Machiavelli
1469–1527
A Florentine analyst of power who separated political judgement from pious appearance and asked how republics and rulers actually survive.
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Modern · Utilitarianism
John Stuart Mill
1806–1873
Mill refined utilitarian ethics while defending individuality, free discussion, representative government, and women’s equality.
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Enlightenment · Feminism
Mary Wollstonecraft
1759–1797
An Enlightenment radical who argued that women’s apparent weakness was produced by education, dependency, and political exclusion.
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Modern · Pragmatism
William James
1842–1910
Psychologist and philosopher who made truth, belief, religion and experience answerable to their consequences in life.
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20th Century · Pragmatism
John Dewey
1859–1952
Dewey recast philosophy as experimental inquiry, joining democracy, education, science and ordinary problem-solving.
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Ancient · Confucianism
Confucius
551–479 BCE
A Chinese teacher of ritual, humane conduct, family responsibility and cultivated judgement whose conversations shaped East Asian moral and political life.
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20th Century · Political philosophy
Hannah Arendt
1906–1975
Examined action, plurality, judgment, totalitarianism, and the fragile public world people build together.
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