The Greatest Philosophers of All Time – Ranked

I found more than 20 lists of the greatest philosophers and combined them into a single meta-list.  The results are below: every philosopher on three or more of the original source lists, presented in rank order (that is, with the philosophers on the most lists at the top).  Although most of the lists were heavily focused on Western philosophy of various sorts, I was also able to find lists of Eastern philosophers and some lists that included both Eastern and Western philosophy.  For each philosopher, I have provided key philosophical schools, ideas and concepts, as well as a list of important books and articles.

NOTE: These are not my personal opinions.  This meta-list is the result of collating multiple lists made by other people.

To see the same list organized chronologically by the philosopher’s date of birth, go here.

On 19 lists
 (Ancient Greece, 428-348 BCE)
Known for: Idealism. Platonism. Theory of Forms. The Allegory of the Cave. The Philosopher-King. Founded the Academy (385 BCE).
Works: Apology (c. 399-390 BCE). Crito (c. 399-390 BCE). Meno (c. 388-367 BCE). Phaedo (c. 388-367 BCE). Symposium (c. 388-367 BCE). The Republic (c. 388-367 BCE).

Bust of Plato in the Centrale Montemartini, Vatican City. Roman copy of a Greek original by Silanion from 428 BCE.

Aristotle (Ancient Greece, 384-322 BCE)
Known for: Realism. Founded the Lyceum (335 BCE). The golden mean. The Four Causes. Democracy.
Works (all written c. 335-323 BCE): Nichomachean Ethics. Poetics. Physics. Politics. Rhetoric. Metaphysics. On the Soul.

Bust of Aristotle in National Museum of Rome. Roman marble copy of Greek bronze original by Lysippos from 330 BCE.

On 18 lists
René Descartes (France, 1596-1650)
Known for: Cartesianism. Rationalism. “Cogito ergo sum.” Cartesian dualism. Mathematical method. Method of normals. Cartestian coordinate system. Foundationalism. Dream argument. Conservation of momentum. Wax argument.
Works: The World (1629-1633, pub. 1662, 1664). Discourse on Method (1637). La Géométrie (1637). Meditations on First Philosophy (1641). Principles of Philosophy (1644). Passions of the Soul (1649).

This late 17th Century copy of Franz Hals’ 1649 portrait of René Descartes is located in the Louvre in Paris.

Immanuel Kant (Germany, 1724-1804)
Known for: Idealism. Synthesizing rationalism and skepticism. Deontological ethics. The categorical imperative. Social contract theory.
Works: Critique of Pure Reason (1781). Prolegomena to Any Future Metaphysics (1783). Groundwork of the Metaphysics of Morals (1785). Critique of Practical Reason (1788). Critique of Judgment (1789).

An 18th Century portrait of Immanuel Kant by an unknown artist.

On 17 lists
Thomas Hobbes (England, 1588-1679)
Known for: Materialism. Empiricism. Social contract theory. Classical realism. Determinism. Ethical egoism. Life in state of nature is “nasty, brutish, and short.”
Works: Elementorum Philosophiae Sectio Tertia de Cive (1642). Leviathan (1651). De Corpore (1655). Behemoth (1668, pub. 1681).

A 17th Century portrait of Thomas Hobbes by John Michael Wright. It is located in the National Portrait Gallery, London.

John Locke (England/GB, 1632-1704)
Known for: Empiricism. Liberalism. Social contract theory. Natural law. Tabula rasa. Primary/secondary qualities. Rights of life, liberty, and property.
Works: Two Treatises of Government (1689). An Essay Concerning Human Understanding (1689). Letters Concerning Toleration (1689-1692). Some Thoughts Concerning Education (1693). On the Conduct of the Understanding (1706).

This 1697 portrait of John Locke by Sir Godfrey Kneller is now located in the State Hermitage Museum in St. Petersburg.

David Hume (UK: Scotland, 1711-1776)
Known for: Empiricism. Skepticism.
Works: A Treatise of Human Nature (1738-1740). An Enquiry Concerning Human Understanding (1748). An Enquiry Concerning the Principles of Morals (1751). Dialogues Concerning Natural Religion (1779).

Allan Ramsay’s 1754 portrait of David Hume is located in the Scottish National Portrait Gallery.

Friedrich Nietzsche (Germany, 1844-1900)
Known for: Idealism. Existentialism. Metaphysical voluntarism. Will to Power. Superman. Anarchism. Apollonian/Dionysian. Resentiment. “God is dead.” Herd instinct. Master-slave morality. Transvaluation of values. Nietzschean affirmation.
Works: The Birth of Tragedy (1872). Human, All Too Human (1878). The Gay Science (1882). Thus Spake Zarathustra (1883). Beyond Good and Evil (1886). On the Genealogy of Morals (1887). Twilight of the Idols (1888). The Antichrist (1888). Ecce Homo (1888).

A photograph of Friedrich Nietzsche from about 1875, taken by F. Hartmann.

On 16 lists
Thomas Aquinas (Tommaso d’Aquino) (Italy, 1225-1274)
Known for: Scholasticism. Thomism. Metaphysical intellectualism. Medieval realism. Omnipotence paradox. Quinque viae. Analogia entis.
Works: Summa contra Gentiles (c. 1259-1265). Summa Theologica (1265-1274). On Being and Essence.

Thomas Aquinas, as depicted by Gentile da Fabriano in a 1400 painting, now in the Pinacoteca di Brera, in Milan.

Baruch Spinoza (Benedict de Spinoza) (Netherlands, 1632-1677)
Known for: Spinozism. Rationalism. Neutral monism. Social contract theory. Pantheism. Determinism. Parallelism. Separation of church and state.
Works: A Short Treatise on God, Man, and His Well-Being (c. 1660). On the Improvement of the Understanding (1662). The Principles of Cartesian Philosophy (1663). Tractatus Theologico-Politicus (1670). Ethics (1674, pub. 1677).

A 1665 portrait of Baruch Spinoza.

Jean-Jacques Rousseau (Switzerland/France, 1712-1778)
Known for: Social contract theory. Romanticism. General will. Child-centered learning. Popular sovereignty. Positive liberty. Amour de soi/amour-propre.
Works: Discourse on the Arts and Sciences (1750). The Social Contract (1762). Émile, or On Education (1762). The Confessions (1781).

A portrait of Jean-Jacques Rousseau by Maurice Quentin de la Tour between 1750 and 1775. It is located in the Musée Antoine Lécuyer in Saint Germaine, France.

On 15 lists
Karl Marx
(Germany/UK, 1818-1883)
Known for: Marxism. Communism. Materialism. Surplus value. Class struggle. Labor theory of value. Alienation and exploitation of labor. Materialist conception of history.
Works: The Communist Manifesto (with Friedrich Engels) (1848). Capital (Das Kapital) (1867-1883).
This photograph of Karl Marx, taken about 1875, is now at the International Institute of Social History in Amsterdam.

Jean-Paul Sartre (France, 1905-1980)
Known for: Existentialism. Marxism. Phenomenology. Hermeneutics. Humanism. Bad faith. “Existence precedes essence.” Transcendence of the ego. Nobel Prize in Literature (1964).
Works: The Transcendence of the Ego (1937). Nausea (1938). Sketch for a Theory of the Emotions (1939). The Imaginary (1940). Being and Nothingness (1943). No Exit (1944). Roads to Freedom (trilogy, 1945-1949). Existentialism Is a Humanism (1946). Search for a Method (1957). Critique of Dialectical Reason (1960).

An undated photo of Jean-Paul Sartre.

On 14 lists
(Ancient Greece, c. 470-399 BCE)
Known for: Rationalism. Persistent critical reflection. Socratic method. “All I know is that I know nothing.”
Works: Apology (by Plato, c. 399-390 BCE). The Socratic Dialogues of Plato (c. 399-367 BCE).

This marble bust of Socrates in the Louvre, Paris is probably a 1st Century CE Roman marble copy of a Greek bronze original by Lysippos.

Augustine of Hippo (Algeria/Roman Empire, 354-430 CE)
Known for: Christian theology. Divine grace. Original sin. Just war theory.
Works: Confessions (c. 397-400 CE). On Christian Doctrine (397-426 CE). The City of God (426 CE).

This portrait of St. Augustine by Peter Paul Rubens, from 1636-1638 is now in the National Gallery of Prague.

John Stuart Mill (UK, 1806-1873)
Known for: Empiricism. Utilitarianism. Classical liberalism. Hierarchy of pleasures. Harm principle. Direct reference theory. Mills’ Methods.
Works: A System of Logic (1843). Essays on Some Unsettled Questions of Political Economy (1844). The Principles of Political Economy (1848). A Few Words on Non-Intervention (1859). On Liberty (1859). Considerations on Representative Government (1861). Utilitarianism (1863). The Subjection of Women (1869). Three Essays on Religion (1874).

A photograph of John Stuart Mill made at the London Stereoscopic Company c. 1870.

Ludwig Wittgenstein (Austria/UK, 1889-1951)
Known for: Analytic philosophy. Linquistic turn. Logical atomism. Picture theory of language. Truth functions. Logical necessity. Ordinary language philosophy. Ideal language analysis.
Works: Tractatus Logico-Philosophicus (1921). Philosophical Investigations (1953). The Blue and Brown Books (1958).

A 1947 photograph of Ludwig Wittgenstein by Ben Richards.

On 13 lists
Gottfried Wilhelm Leibniz
 (Germany, 1646-1716)
Known for: Rationalism. Monads. Philosophical optimism. “Best of all possible worlds.” “Why is there something rather than nothing?” Symbolic logic.
Works: Discourse on Metaphysics (1686). New Essays Concerning Human Understanding (1704). Théodicée (1710). Monadology (1714).

A portrait of Gottfried Leibniz by Christoph Bernhard Francke from the 1720s.

Georg Wilhelm Friedrich Hegel (Germany, 1770-1831)
Known for: Idealism. Romanticism. Naturphilosophie. Historicism. Dialectical phenomenology.
Works: Phenomenology of Spirit (1807). Science of Logic (1812–1816). Elements of the Philosophy of Right (1821). Lectures on the Philosophy of History (1837).

This 1831 portrait of Hegel by Jakob Schlesinger is located at the Alte Nationalgalerie in Berlin.

On 12 lists
(China, 551-479 BCE)
Known for: Confucianism. The Golden Rule.
Works: The Analects (attrib.) (c. 475-221 BCE).

An imagining of Confucius made by Wu Daozi (c. 680-760 CE) during the Tang Dynasty.

Arthur Schopenhauer (Germany, 1788-1860)
Known for: Idealism. Anthropic principle. Philosophical pessimism. Transcendental idealism. Metaphysical voluntarism. Antinatalism. Eternal Justice. Hedgehog’s dilemma. Principium individuationis. Will as thing in itself.
Works: On the Fourfold Root of the Principle of Sufficient Reason (1813). The World as Will and Representation (Vol. 1: 1819; Vol. 2: 1844). The Art of Being Right (1831). On the Will in Nature (1836). On the Freedom of the Will (1839). On the Basis of Morality (1840). Parerg and Paralipomena (1851).

An 1859 photograph of Arthur Schopenhauer by Johann Schäfer.

Søren Kierkegaard (Denmark, 1813-1855)
Known for: Existentialism. Christian theology. Angst. Knight of faith. Recollection and repetition. Three stages on life’s way. Subjectivity is truth.
Works: Either/Or (1843). Fear and Trembling (1843). The Concept of Anxiety (1844). Concluding Unscientific Postscript to Philosophical Fragments (1846). The Sickness Unto Death (1849).

An 1840 unfinished sketch of Søren Kierkegaard by his cousin Niels Christian Kierkegaard.

Bertrand Russell (UK, 1872-1970)
Known for: Analytic philosophy. Linguistic turn. Logicism. Utilitarianism. Descriptivist theory of names. Epistemic structural realism. Nobel Prize in Literature (1950).
Works: “On Denoting” (1905). The Problems of Philosophy (1912). Principia Mathematica (with Alfred North Whitehead) (1910-1913). Why I Am Not a Christian (1927). An Inquiry into Meaning and Truth (1940). A History of Western Philosophy (1945). Logic and Knowledge: Essays 1901-1950 (1956).

A 1935 photograph of Bertrand Russell by Granger.

Martin Heidegger (Germany, 1889-1976)
Known for: Phenomenology. Existentialism. Ontological hermeneutics. Dasein.
Works: Being and Time (1927). Introduction to Metaphysics (1935, pub. 1953). Contributions to Philosophy (1936-1938, pub. 1989).

An undated photograph of Martin Heidegger.

Simone de Beauvoir (France, 1908-1986)
Known for: Existentialism. Existential phenomenology. Marxism. Feminism.
Works: The Ethics of Ambiguity (1947). The Second Sex (1949). The Coming of Age (1970).
A 1946 photograph of Simon de Beauvoir by Henri Cartier-Bresson.

On 11 lists
Francis Bacon
(The Viscount St. Alban) (England, 1561-1626)
Known for: Empiricism. The scientific method. Inductive reasoning.
Works: Essays (1st Ed., 1597). The Advancement and Proficience of Learning Divine and Human (1605). Essays (2nd Ed., 1612). Novum Organum Scientarium (1620). New Atlantis (1627).

A 1617 portrait of Francis Bacon by Frans Pourbus.

William James (US, 1842-1910)
Known for: Pragmatism. Functional psychology. Radical empiricism. Will to Believe Doctrine. James-Lange theory of emotion.
Works: “What Is an Emotion?” (1884). The Principles of Psychology (1890). The Will to Believe (1897). The Varieties of Religious Experience (1902). Pragmatism (1907). Essays in Radical Empiricism (1912).

A 1903 photograph of William James made at Notman Studios.

Edmund Husserl (Austria/Germany, 1859-1938)
Known for: Phenomenology. Logical objectivism. Epoché. Eidetic reduction. Lebenswelt. Pre-reflective self-consciousness. Transcendental subjectivism.
Works: Logical Investigations (1900). Ideas Pertaining to a Pure Phenomenology and to a Phenomenological Philosophy (1st Book, 1913). Cartesian Meditations (1931). The Crisis of European Sciences and Transcendental Phenomenology (1936).

A photograph of Edmund Husserl c. 1900.

On 10 lists
Niccolò Machiavelli
(Italy, 1469-1527)
Known for: Renaissance humanism. Political realism. Classical republicanism.
Works: The Art of War (1519-1520). Discourses on Livy (1531). The Prince (1532).
This posthumous portrait of Niccolò Machiavelli by Santi di Tito from 1550-1603 is now in the Palazzo Vecchio in Florence, Italy.

George Berkeley (Bishop Berkeley) (Ireland/GB, 1685-1753)
Known for: Empiricism. Subjective idealism. Skepticism.
Works:  An Essay Toward a New Theory of Vision (1709). A Treatise Concerning the Principles of Human Knowledge (1710). Three Dialogues between Hylas and Philonous (1713). Alciphron (1732). The Analyst (1734).

This portrait of George Berkeley by John Smibert from c. 1730 is now in the National Portrait Gallery in London.

On 9 lists
(Ibn Sina) (Persia, 980-1037 CE)
Known for: Neoplatonism. Avicennism. Proof of the Truthful. Floating Man thought experiment.
Works: alHikma al– ‘Arudiya (Philosophy for the Prosodist). The Canon of Medicine (1025). Kitāb al-shifā (The Book of Healing; The Cure) (1020). Kitāb al-Najāt (The Book of Deliverance; The Book of Salvation) (11th Century). The Book of Knowledge for ‘Ala al-Dawla. Remarks and Admonitions.

An artist’s imagining of Ibn Sina, also known as Avicenna.

Voltaire (François-Marie Arouet) (France/Switzerland, 1694-1778)
Known for: Deism. Freedom of religion. Freedom of speech. Separation of church and state.
Works: Letters Concerning the English Nation (1734). Elements of the Philosophy of Newton (1745). Zadig (1747). Essays on the Customs and the Spirit of the Nations (1756).  Candide (1759).
Philosophical Dictionary (1764).

This portrait of Voltaire by Nicolas de Largillière from 1724-1725 is now located at the Palace of Versailles in France.

Jeremy Bentham (GB, 1748-1832)
Known for: Utilitarianism. Legal positivism. Liberalism. Greatest happiness principle.
Works: A Fragment on Government (1776). An Introduction to the Principles of Morals and Legislation (1780). Defence of Usury (1787). Anarchical Fallacies (1796).

This portrait of Jeremy Bentham by Henry William Pickersgill from c. 1829 is now in the National Portrait Gallery in London.

John Dewey (US, 1859-1952)
Known for: Pragmatism. Reflective thinking. Immediate empiricism. Educational progressivism. Occupational psychosis.
Works: “The Reflex Arc Concept in Psychology” (1896). The School and Society (1899). Democracy and Education (1916). Human Nature and Conduct (1922). Experience and Nature (1925). The Public and its Problems (1927). Art as Experience (1934). Logic: The Theory of Inquiry (1938). Freedom and Culture (1939). Knowing and the Known (with Arthur Bentley) (1949).

An undated photograph of John Dewey.

Hannah Arendt (Germany/US, 1906-1975)
Known for: Existential phenomenology. Classical republicanism. The banality of evil.
Works: The Origins of Totalitarianism (1951). The Human Condition (1958). Eichmann in Jerusalem: A Report on the Banality of Evil (1963). On Revolution (1963). Men in Dark Times (1968). On Violence (1970). The Life of the Mind (1978).

An undated photograph of Hannah Arendt.

Michel Foucault (France, 1926-1984)
Known for: Post-structuralism. Discourse analysis. Discursive formation. Panopticism. Subjectivation.
Works: The History of Madness (1961). The Birth of the Clinic (1963). The Order of Things (1966). The Archaeology of Knowledge (1969). Discipline and Punish (1975). The History of Sexuality (1976).

A photograph of Michel Foucault c. 1965.

On 8 lists
Laozi (Lao-Tzu) (China, c. 600-531 BCE)
Known for: Taoism
Works: Tao Te Ching (Daodejing) (attrib.) (c. 624-604 BCE).

Song Dynasty stone sculpture of Laozi at the foot of Mount Qingyuan (960-1279).

Parmenides (Ancient Greece, born c. 515 BCE)
Known for: Eliatic school. Rationalism. “Thought and being are the same.” Nothing comes from nothing. The Void. The impossibility of change. The unchanging nature of existence.
Works: On Nature (c. 5th Century BCE).

This bust of Parmenides, possibly from the 1st Century CE, was discovered at the Velia archaeological site in Italy in 1962.

Epicurus (Ancient Greece, 341-270 BCE)
Known for: Epicureanism. Atomism. Materialism. Hedonism. Pleasure principle. Atomic swerve.
Works: On Nature (fragments only) (late 4th Century-early 5th Century BCE). Letters (quoted in Lives of Eminent Philosophers, by Diogenes Laërtius, c. 250 CE).

This marble bust of Epicurus is a Roman copy of a Greek original from the 2nd or 3rd Century BCE. It is now in the British Museum in London.

Willard Van Orman Quine (US, 1908-2000)
Known for: Analytic philosophy. Indeterminacy of translation. Naturalized epistemology. Ontological relativity. Quine-Putnam indispensability thesis.
Works: “On What There Is” (1948). “Two Dogmas of Empiricism” (1951). From a Logical Point of View (1953). Word and Object (1960). “Epistemology Naturalized” (1969). The Roots of Reference (1971).

An undated photograph of Willard Van Orman Quine.

On 7 lists
(Ancient Greece, 535-475 BCE)
Known for: Unity of opposites. Logos. The upward-downward path. “Everything flows.” “Character is fate.” “Strife is justice.”
Works: On Nature (quoted in Lives of Eminent Philosophers, by Diogenes Laërtius, c. 250 CE).

An unknown 17th Century artist’s imagining of Heraclitus.

Marcus Aurelius (Roman Empire, 121-180 CE)
Known for: Stoicism.
Works: Meditations (180 CE).

This Ancient Roman marble bust of Marcus Aurelius is located in the Istanbul Archaeological Museum in Turkey.

Plotinus (Egypt/Roman Empire, c. 204-270 CE)
Known for: Neoplatonism. Emanations from the One: Nous, World Soul, Human Souls, Matter. Three hypostases: the One, Intellect, and Soul. Henosis (union with the One).
Works: The Enneads (c. 270 CE).

One of four marble heads, believed to be Plotinus, found at Ostia Antica in Italy.

Averroes (Ibn Rushd) (Spain/Morocco, 1126-1198)
Known for: Aristotelianism. Maliki. Reconciling Aristotelianism with Islam.
Works: The Incoherence of the Incoherence (1180). Commentaries on Aristotle (numerous). On the Intellect. On the Syllogism. On Conjunction with the Active Intellect. On Time. On the Heavenly Sphere. On the Motion of the Sphere.

Florentine artist Andrea di Bonaiuto da Firenze’s imagining of Averroes, shown in detail from his fresco Triunfo de Santo Tomás de Aquino, from 1365-1368, which is located in the Santa Maria Novella church in Florence, Italy.

Auguste Comte (Isidore Marie Auguste François Xavier Comte) (France, 1798-1857)
Known for: Positivism. Praxeology. Religion of humanity. Law of three stages. Altruism.
Works: The General Separation of Opinions and Desires (1819). Plan of Scientific Studies Necessary for the Reorganization of Society (1822). The Course in Positive Philosophy (1830-1842). A General View of Positivism (1848). Système de politique positive (1851–1854). The Subjective Synthesis, Vol. 1 (1856).

An undated photograph/drawing of August Comte. Hulton Archive/Getty Images

Karl Popper (Austria/New Zealand/UK, 1902-1994)
Known for: Critical rationalism. Realism. Liberalism. Empirical falsification. Cosmological pluralism. Objective hermeneutics. Negative utilitarianism.
Works: The Logic of Scientific Discovery (1934). The Poverty of Historicism (1944). The Open Society and Its Enemies (1945). Conjectures and Refutations (1963). Objective Knowledge (1972). The Self and its Brain (with John Eccles) (1977).

A 11990 photograph of Karl Popper.

On 6 lists
(Mo Tzu) (China, c. 470-391 BCE)
Known for: Mohism. Impartial caring. Enlightened self-interest. Consequentialism.
Works: Mozi (attrib.) (c. 476-221 BCE).

A drawing of Mozi.

Mencius (China, 372-289 BCE)
Known for: Confucianism. Innate goodness.
Works: The Book of Mencius (c. 309-289 BCE).

A posthumous portrait of Mencius.

Anselm of Canterbury (Anselm of Aosta) (France/England, c. 1033-1109)
Known for: Scholasticism. Christian theology. Ontological argument. Satisfaction theory of atonement.
Works: Monologion (1075-1076). Proslogion (1077-1078). Cur Deus Homo (1095-1098).
A late 16th Century engraving of Anselm of Canterbury.

Blaise Pascal (France, 1623-1662)
Known for: Jansenism. Pascal’s triangle. Pascal’s identity.
Works: “Of the Geometrical Spirit” (1657/1658). The Provincial Letters (1656-1657). Pensées (1669).

A copy of Francois II Quesnel’s portrait of Blaise Pascal c. 1691. It is now in the Palace of Versailles in France.

Charles Sanders Peirce (US, 1839-1914)
Known for: Pragmatism. Abductive reasoning. Continuity. Tychism. Synechism. Fallibilism. Scholastic realism. Objective idealism. Logic precedes metaphysics. Logic as formal semiotic. The Four Incapacities.
Works: “On the Natural Classification of Arguments” (1867). “On a New List of Categories” (1867). “Upon the Logic of Mathematics” (1867).”Upon Logical Comprehension and Extension” (1867). “Nominalism versus Realism” (1868). “Questions concerning certain Faculties claimed for Man” (1868). “Some Consequences of Four Incapacities” (1868). “What is Meant by ‘Determined‘” (1868) “Grounds of Validity of the Laws of Logic: Further Consequences of Four Incapacities” (1869). Logic of Relatives (1970). “The Fixation of Belief” (1877). “How to Make Our Ideas Clear” (1878). “The Doctrine of Chances” (1878). “The Probability of Induction” (1878). “The Order of Nature” (1878). “Deduction, Induction, and Hypothesis” (1878). The Architecture of Theories (1891). The Doctrine of Necessity Examined (1892). The Law of Mind (1892). What Pragmatism Is (1905). Issues of Pragmaticism (1905).

An undated photograph of Charles Sanders Peirce.

Gottlob Frege (Friedrich Ludwig Gottlob Frege) (Germany, 1848-1925)
Known for: Analytic philosophy. Logical objectivism. Logicism. Transcendental idealism. Realism. Axiomatic predicate logic. Quantified variables. Principle of compositionality. Context principle.
Works: Begriffsschrift (1879). The Foundation of Arithmetic (1884). “On Sense and Reference” (1892). “Concept and Object” (1892). “What Is a Function?” (1904). “The Thought” (1918-1919). “Negation” (1918-1919).

A photograph of Gottlob Frege c. 1879.

G.E. Moore (George Edward Moore) (UK, 1873-1958)
Known for: Analytic philosophy. Common sense. Moral intuition. Naturalistic fallacy. Paradox of analysis. Transparency of consciousness. Moore’s Paradox. Principle of organic unity.
Works: “The Nature of Judgment” (1899). “The Refutation of Idealism” (1903). Principia Ethica (1903). “The Nature and Reality of the Objects of Perception” (1905-1906). Ethics (1912). “Some Judgments of Perception” (1918). “Are the Characteristics of Things Universal or Particular?” (1923). “A Defence of Common Sense” (1925). Philosophical Papers (including “Proof of an External World”) (1959).

An undated photograph of G.E. Moore.

Albert Camus (Algeria/France, 1913-1960)
Known for: Existentialism. Absurdism. Anarchism. Nobel Prize in Literature (1957).
Works: The Stranger (1942). The Myth of Sisyphus (1942). The Plague (1947). The Rebel (1951).

An undated photograph of Albert Camus.

John Rawls (US, 1921-2002)
Known for: Liberalism. Justice as fairness. The original position. Reflective equilibrium. Overlapping consensus.
Works: A Theory of Justice (1971). Political Liberalism (1993). The Law of Peoples (1999).
An undated photograph of John Rawls, first published in the Harvard Gazette.

Jürgen Habermas (Germany, 1921- )
Known for: Critical theory. Pragmatism. Communicative rationality. Discourse ethics. Universal pragmatics. Rational reconstruction. Performative contradiction.
Works: The Structural Transformation of the Public Sphere (1962). Knowledge and Human Interests (1968). The Theory of Communicative Action (1981). “Modernity versus Postmodernity” (1981). The Philosophical Discourse of Modernity (1985). Between Facts and Norms: Contributions to a Discourse Theory of Law and Democracy (1992). The Inclusion of the Other (1996).

An undated photograph of Jürgen Habermas.

Noam Chomsky (US, 1928- )
Known for: Analytic philosophy. Cognitive science. Universal grammar. Generative grammar. Chomsky hierarchy. Minimalist Program.
Works: Logical Structure of Linguistic Theory (1955). Syntactic Structures (1957). Current Issues in Linguistic Theory (1964). Aspects of the Theory of Syntax (1965). The Political Economy of Human Rights (1979). Manufacturing Consent: The Political Economy of the Mass Media (1988). Necessary Illusions: Thought Control in Democratic Societies (1989). The Minimalist Program (1995). Objectivity and Liberal Scholarship (1997).

An undated photograph of Noam Chomsky.

Jacques Derrida (Algeria/France, 1930-2004)
Known for: Post-structuralism. Deconstruction. Radical hermeneutics.
Works: Of Grammatology (1967). Speech and Phenomena (1967). Writing and Difference (1978). The Post Card: From Socrates to Freud and Beyond (1980). Margins of Philosophy (1982). Of Spirit: Heidegger and the Question (1987). Limited Inc. (including “Signature Event Context”) (1988). On the Right to Philosophy (1990).

An undated photograph of Jacques Derrida.

Richard Rorty (US, 1931-2007)
Known for: Pragmatism. Postanalytic philosophy. Postphilosophy. Ironism. Final vocabulary. Epistemological behaviorism. Antirepresentationalism.
Works: Philosophy and the Mirror of Nature (1979). Consequences of Pragmatism (1982). Contingency, Irony, and Solidarity (1989). Objectivity, Relativism, and Truth (1990). Philosophy and Social Hope (1999). Philosophy as Cultural Politics (2007).

A photograph of Richard Rorty by Steve Pyke, from between 1988 and 1991.

Saul Kripke (US, 1940- )
Known for: Analytic philosophy. Kripke-Platek set theory. Theories of reference. Admissible ordinal. Kripke structure. Kripke semantics. Disquotational principle. Accessibility relation. Rule-following paradox. Necessary a priori truths.
Works: “Semantical Considerations on Modal Logic” (1963). “Outline of a Theory of Truth” (1975). “A Puzzle About Belief” (1979). Naming and Necessity (1980). Wittgenstein on Rules and Private Language (1982).

An undated photograph of Saul Kripke at the beach.

On 5 lists
The Buddha (Siddhartha Gautama) (India, c. 563/480–483/400 BCE)
Known for: Buddhism. The Middle Way. Dhyana. Impermanence. Dependent origination. Liberating insight.
Works: Sutta Pitkata (attrib.) (including Khuddaka Nikaya/Dhammapada) (29 BCE).

Sandstone sculpture of Buddha Preaching the Law (Dharmacakra mudrā) from the Gupta Period (240-590 CE). It is located in the Sarnath Archaeological Museum in Sarnath, India.

Zeno of Elea (Ancient Greece, c. 490-430 BCE)
Known for: Eleatic School. Zeno’s Paradoxes. Dialectic. Reductio ad absurdum.
Works: Parmenides (by Plato) (c. 380 BCE). Physics (by Aristotle) (c. 335 BCE). Live and Opinions of Eminent Philosophers (by Diogenes Laërtius) (c. 250 CE).

An undated etching of a bust of Zeno of Elea.

Sun Tzu (Sunzi) (Sun Wu (?)) (China, c. 544-496 BCE (traditional), c. 450-380 BCE (?))
Known for: Military theory. Know when to fight and not to fight. Timing is essential. Know yourself and your enemy. “All warfare is based on deception.” The best victories come through means other than warfare. “In the midst of chaos, there is opportunity.” Success breeds success. Prolonged warfare does not benefit nations.
Works: The Art of War (attrib.) (c. 500-450 BCE (earliest version); c. 400-300 BCE (revisions and additions by Sun Bin (?))

A statue of Sun Tzu in Yurihama, Tottori, Japan.

Adi Shankara (Adi Shankaracharya) India, c. 788–820 CE)
Known for: Hinduism. Dashanami Sampradaya. Advaita Vedanta. Unity of the ātman and Nirguna Brahman.
Works: Brahmasutrabhasya (Commentary on the Brahma Sutras). Bhagavadgītabhasya (Commentary on the Bhagavad Gita). Upadesasahasri.

An artist’s imagining of Adi Shankara.

Ramanuja (India, c. 1017–1137)
Known for: Hinduism. Sri Vaisnavism. Vishishtadvaita Vedanta. Qualified monism.
Works: Shri Bhāshya. Vedārthasangraha. Bhagavad Gita Bhāshya.

An artist’s imagining of Ramanuja.

Al-Ghazali (Persia, 1058-1111)
Known for: Ash’ari Islam. Sufism. Theological occasionalism.
Works:  Deliverance from Error (c. 1100). Aims of the Philosophers. The Incoherence of the Philosophers (Tahāfut al-Falāsifa).  Criterion of Knowledge in the Art of Logic. Touchstone of Reasoning in Logic. The Correct Balance. The Revival of Religious Sciences (The Alchemy of Happiness).

An artist’s imagining of Al-Ghazali.

Duns Scotus (John Duns) (Scotland, 1266-1308)
Known for: Scholasticism. Theological voluntarism. Medieval realism. Univocity of being. Haecceity as principle of individuation. Immaculate Conception of Mary.
Works: Quaestiones super libros Metaphysicorum Aristotelis (c. 1298-1300). Ordinatio (Opus Oxoniense) (c. 1300-1304). Lectura (c. 1300-1304). Reportatio parisiensis (c. 1302-1307). Quaestiones Quodlibetales (c. 1306-1307). Notabilia Scoti super Metaphysicam. Treatise on the First Principle (De primo principio).

This late 15th Century portrait of Duns Scotus by Justus van Gent is now at the Palazzo Barberini in Rome.

William of Ockham (England, 1285-1347)
Known for: Scholasticism. Theological voluntarism. Fideism. Conceptualism/Nominalism. Occam’s Razor.
Works: Commentary on the Sentences of Peter Lombard (1317-1318). Little Summa of Natural Philosophy (1319-1321). Summa logicae (Sum of Logic) (c. 1323). Brief Summa of the Physics (1322–1323). Exposition of Aristotle’s Physics (1322–1324). Questions on Aristotle’s Books of the Physics (before 1324).

An artist’s imagining of William of Ockham in stained glass at a church in Surrey, England.

Montesquieu (Charles-Louis de Secondat, Baron de La Brède et de Montesquieu) (France, 1689-1755)
Known for: Enlightenment. Liberalism. Separation of powers.
Works: Persian Letters (1721). True History (c. 1723-1738). The Spirit of the Laws (1748).
An undated engraving of Montesquieu.

Denis Diderot (France, 1713-1784)
Known for: Materialism. Encyclopédistes. Enlightenment. Experimental science.
Works: Philosophical Thoughts (1746). The Skeptic’s Walk (1747). Letter on the Blind (1749). On the Interpretation of Nature (1754). Encyclopédie (1751-1765). Rameau’s Nephew (1763). D’Alembert’s Dream (1769). Jacques the Fatalist (1773). Paradox of the Actor (1770-1778).

This 1767 portrait of Denis Diderot by Louis-Michel van Loo is now located in the Louvre in Paris.

Mary Wollstonecraft (GB, 1759-1797)
Known for: Women’s rights. Co-education.
Works: Thoughts on the Education of Daughters (1787). A Vindication of the Rights of Men (1790). A Vindication of the Rights of Woman (1792).

John Opie’s portrait of Mary Wollstonecraft, from about 1797, is now in the National Portrait Gallery, London.

Henri Bergson (France, 1859-1941)
Known for: Spiritualism. Immediate experience. Intuition. Theory of Duration. Lebensphilosophie. Élan vital. Nobel Prize in Literature (1927).
Works: Time and Free Will (1889). Matter and Memory (1896). Laughter: An Essay on the Meaning of the Comic (1900). Creative Evolution (1907).

A 1927 photograph of Henri Bergson.

Alfred North Whitehead (UK/US, 1861-1947)
Known for: Process philosophy. Process theology. Extensive abstraction. Fallacy of misplaced concreteness. Prehension.
Works: A Treatise on Universal Algebra (1898). Principia Mathematica (with Bertrand Russell) (1910-1913). An Introduction to Mathematics (1911). An Enquiry Concerning the Principles of Natural Knowledge (1919). The Concept of Nature (1920). Process and Reality (1929).

An undated photograph of Alfred North Whitehead.

Rudolf Carnap (Germany/US, 1891-1970)
Known for: Analytic philosophy. Logical atomism. Logical positivism. Physicalism. Confirmationism. Beobachtungssatz (observational statement). Carnap’s categoricity. “Every complete axiom system is also categorical.” Epistemic structural realism. Ramsay sentences.
Works: The Logical Structure of the World (1928). The Logical Syntax of Language (1934). Philosophy and Logical Syntax (1935). Introduction to Semantics (1942). “On Inductive Logic” (1945). “The Two Concepts of Probability” (1945). “On the Application of Inductive Logic” (1947). Meaning and Necessity (1947). “Empiricism, Semantics, Ontology” (1950). The Continuum of Inductive Methods (1952). Philosophical Foundations of Physics (1966).

An undated photograph of Rudolf Carnap.

Theodor W. Adorno (Theodor Ludwig Wiesengrund) (Germany, 1903-1969)
Known for: Critical theory. Western Marxism. Paradox of aesthetics. Maturity. Negative dialectics.
Works: Dialectic of Enlightenment (with Max Horkheimer) (1944). Philosophy of New Music (1949). The Authoritarian Personality (1950). Minima Moralia (1951). Against Epistemology (1956). Negative Dialectics (1966). Aesthetic Theory (1970).

An undated photograph of Theodor Adorno.

Peter Singer (Australia, 1946- )
Known for: Analytic philosophy. Utilitarianism. Equal consideration of interests. Drowning child analogy. Effective altruism.
Works: “Famine, Affluence, and Morality” (1972). Animal Liberation (1975). Practical Ethics (1979). How Are We to Live? Ethics in an Age of Self-Interest (1993). Rethinking Life and Death: The Collapse of Our Traditional Ethics (1994). A Darwinian Left (1999). One World: The Ethics of Globalisation (2002). The Life You Can Save: Acting Now to End World Poverty (2009). The Point of View of the Universe (with Karazyna de Lazari-Radek) (2014). The Most Good You Can Do (2015).

A 2015 photograph of Peter Singer by Tristan Martin/THOMSON REUTERS FOUNDATION.

Judith Butler (US, 1956- )
Known for: Critical theory. Post-structuralism. Postmodernism. Third-wave feminism. Queer theory. Performative turn. Gender as social construction. Gender performativity.
Works: “Performative Acts and Gender Constitution” (1988). “Imitation and Gender Insubordination” (1990). Gender Trouble: Feminism and the Subversion of Identity (1990). Bodies that Matter: On the Discursive Limits of Sex (1993). Excitable Speech: A Politics of the Performative (1997). Undoing Gender (2004). Precarious Life: The Powers of Mourning and Violence (2004). Giving An Account of Oneself (2005). Senses of the Subject (2015). Notes Toward a Performative Theory of Assembly (2015).

A 2012 photograph of Judith Butler.

On 4 lists
Pythagoras (Ancient Greece, c. 570-495 BCE)
Known for: Pythagoreanism. Communalism. Metempsychosis. Musica universalis. Pythagorean theorem (attrib.). Sphericity of the Earth (attrib.). Five regular solids (attrib.). Theory of Proportions (attrib.).
Works: Lives and Opinions of Eminent Philosophers (by Diogenes Laërtius) (c. 250 CE).

Bust of Pythagoras from Musei Capitolini, Rome. Marble Roman copy of a 5th Century BCE Greek bronze original.

Democritus (Ancient Greece, 460-360 BCE)
Known for: Atomism. Causality. Materialism. Atomistic void. “Equality is everywhere noble.” Legitimate vs. bastard knowledge.
Works: Lives and Opinions of Eminent Philosophers (by Diogenes Laërtius) (c. 250 CE). Source Book in Ancient Philosophy (Charles Montague Bakewell, ed.) (1907).
This marble bust of Democritus, which is located at the Victoria and Albert Museum in London, is attributed to an unknown 18th Century Italian artist.

Zhuang Zhou (Zhuangzi) (China, c. 369-286 BCE)
Known for: Taoism (Daoism). “The Butterfly Dream.” “The Death of Wonton.” “The Debate on the Joy of Fish.” “Drumming on a Tub and Singing.”
Works: The Book of Zhuangzi (c. 306-286 BCE).

An artist’s imagining of Zhuang Zhou.

Patanjali (India, c. 200 BCE-300 CE)
Known for: Hinduism. Samadhi. Sadhana. Vibhuti. Kaivalya. Eight components of yoga (Yamas, Niyama, Asana, Pranayama, Pratyahara, Dharana, Dhyana, Samadhi).
Works: Yoga Sutras (attrib.) (before 400 CE).

A modern sculpture of Patanjali at Patanjali Yogpeeth in Haridwar, India.

Seneca the Younger (Lucius Annaeus Seneca) (Roman Empire, c. 4 BCE – 65 CE)
Known for: Stoicism.
Works: De Ira (On anger) (41 CE). De Brevitate Vitæ (On the shortness of life) (49 CE). De Constantia Sapientis (On the Firmness of the Wise Person) (55 CE). De Vita Beata (On the Happy Life) (58 CE). De Otio (On Leisure) (62 CE). De Tranquillitate Animi (On tranquillity of mind) (63 CE). Naturales quaestiones (63 CE). De Providentia (On providence) (64 CE). Moral Epistles (Epistulae Morales ad Lucilium) (c. 65 CE).

This Roman marble bust of Seneca, one side of a Double Herm of Socrates and Seneca, dates to the first half of the 3rd Century CE. It is now located at the Pergamon Museum in Berlin.

Nagarjuna (India, c. 150–250 CE)
Known for: Mahayana Buddhism. Madhyamaka school. Prajñāpāramitā sutras. Sunyata (emptiness). Two truths doctrine. Causality. Relativity.
Works: Mūlamadhyamakakārikā (attrib). Śūnyatāsaptati (Seventy Verses on Emptiness). Vigrahavyāvartanī (The End of Disputes). Vaidalyaprakaraṇa (Pulverizing the Categories). Vyavahārasiddhi (Proof of Convention).

This 17th Century statue of Nagarjuna by Tibetan artist Tsapa Namjyal is now located at the Walters Art Museum in Baltimore, Maryland.

Boethius (Anicius Manlius Severinus Boëthius) (Italy, c. 480-524 CE)
Known for: Neoplatonism. The Wheel of Fortune.
Works: De arithmetica (c. 500 CE) De institutione musica (c. 510 CE). The Consolation of Philosophy (c. 524). De topicis differentiis (c. 522-523 CE). De Trinitate (c. 520-521 CE). Quomodo substantiae.

Cover illustration of Boethius from a 12th Century copy of his book, De Institutione Musica. The manuscript is located at the Cambridge University Library.

Al-Farabi (Afghanistan/Persia/Egypt/Iraq/Syria (?), c. 872-950 CE)
Known for: Farabism (Alfarabism). Neo-Aristotelianism. Neoplatonism. Future contingents. Conditional syllogisms. Analogical inference.
Works: Kitāb al-mūsīqa (The Great Book of Music). Al-Madīna al-Fāḍila (Principles of the Opinions of the Citizens of the Virtuous City). Kitāb iḥṣāʾ al-ʿulūm (On the Introduction of Knowledge). Kitāb iḥṣāʾ al-īqā’āt (Classification of Rhythms). “On Vacuum.” Social Psychology. Commentary and Short Treatise on Aristotle’s de Interpretatione.

An artist’s imagining of Al-Farabi.

Peter Abelard (France, 1079-1142)
Known for: Scholasticism. Conceptualism.
Works: Petri Abaelardi Glossae in Porphyrium (The Glosses of Peter Abailard on Porphyry) (c. 1120). Logica ingredientibus (Logic for Beginners) (before 1121). Dialectica (before 1125). Logica nostrorum petitioni sociorum (Logic in response to the request of our comrades) (c. 1124-1125). Tractatus de intellectibus (A Treatise on Understanding) (before 1128). Sic et Non (Yes and No). Theologia ‘Summi Boni’ Theologia christiana (c. 1120-1140). Theologia ‘scholarium’ (c. 1120-1140). Dialogus inter philosophum, Judaeum, et Christianum, (Dialogue of a Philosopher with a Jew and a Christian) (1136–1139). Ethica or Scito Te Ipsum (Ethics, or Know Yourself) (before 1140).

A stone statute of Peter Abelard by Jules Cavelier, made before 1853, now stands in the Louvre, in Paris.

Zhu Xi (China, 1130–1200)
Known for: Confucianism. Neo-Confucianism. Vital force (qi). Principle (li). The Supreme Ultimate (taiji). The investigation of things. Heart/mind. Knowledge/action.
Works: Commentary on the Four Books (c. 1180-1200). Classified Dialogues of Master Zhu (Zhuzi yulei). Daxue (Great Learning). Collected Writings of Zhu Xi (Zhuzi wenji). Reflections on Things at Hand (Jinsilu).

An artist’s imagining of Zhu Xi.

Maimonides (Moses ben Maimon) (Spain/Egypt, 1135-1204)
Known for: Judaism. Jewish scholasticism. Negative theology. True beliefs vs. necessary beliefs.
Works: Commentary on the Mishna (1168). Guide for the Perplexed (c. 1186-1190). Treatise on Logic (attrib.).

In 1985, Paraguay issued a stamp with the image of Maimonides.

Nichiren (Japan, 1222–1282)
Known for: Nichiren Buddhism. Mahayana. Tendai. Nam Myōhō Renge Kyō chanting. The Five Guides of Propagation. The Three Great Secret Dharmas. The Three Proofs.
Works: On Establishing the Correct teaching for the Peace of the Land (Rissho Ankoku Ron) (c. 1258-1260). The Opening of the Eyes (Kaimoku-sho) (1272). The Object of Devotion for Observing the Mind (Kanjin-no Honzon-sho) (1273). The Selection of the Time (Senji-sho) (1275). On Repaying Debts of Gratitude (Ho’on-sho) (1276).

This painting of Nichiren from the 14th or 15th century is located in a Buddhist temple in Kuon-ji, Japan.

Wang Yangming (China, 1472–1529)
Known for: Neo-Confucianism. School of Mind. Innate knowing. Unity of knowing and acting.
Works: Instructions for Practical Living. Record of Discourses. Inquiry Regarding the Great Learning.

A painting of Wang Yangming.

Thomas Paine (GB/France/US, 1737-1809)
Known for: Enlightenment. Liberalism. Republicanism.
Works: Common Sense (1776). The American Crisis (1776-1783). The Rights of Man (1791-1792). The Age of Reason (1793-1794). Agrarian Justice (1797).

This c. 1792 portrait of Thomas Paine by Laurent Dabos is now at the National Portrait Gallery in Washington, D.C.

Mao Zedong (China, 1893–1976)
Known for: Maoism. Marxism. New Democracy. People’s War. Mass line. Three Worlds Theory. Agrarian socialism.
Works: Strategic Problems of China’s Revolutionary War (1936). On Guerilla Warfare (1937). On Practice (1937). On Contradiction (1937). On Protracted War (1938). On New Democracy (1940). Dialectical Materialism (1940). Serve the People (1944). Quotations from Chairman Mao Tse-Tung (1964).

A 1939 photograph of Mao Zedong.

Maurice Merleau-Ponty (France, 1908-1961)
Known for: Phenomenology. Western Marxism. Structuralism. Post-structuralism. Anonymous collectivity. Motor intentionality. The flesh of the world. “The perceiving mind is the incarnated mind.” Invagination.
Works: The Structure of Behavior (1942). Phenomenology of Perception (1945). Humanism and Terror (1947). Sense and Non-Sense (1948). Consciousness and the Acquisition of Language (1949-1940). In Praise of Philosophy (1953). Phenomenology and the Sciences of Man (1958). Signs (1960). The Visible and the Invisible (1964).

An undated photograph of Maurice Merleau-Ponty.

Gilles Deleuze (France, 1925-1995)
Known for: Post-structuralism. Postmodernism. Affect. Assemblage. Deterritorialization. Line of flight. Plane of immanence. Schizoanalysis. Transcendental empiricism. Univocity of being. The Virtual.
Works: Difference and Repetition (1968). The Logic of Sense (1968). Capitalism and Schizophrenia: Anti-Oedipus (with Félix Guattari) (1972). “One Less Manifesto” (with Carmelo Bene) (1978). A Thousand Plateaus (with Félix Guattari) (1980). Negotiations (1990). Essays Critical and Clinical (1993).

An undated photograph of Gilles Deleuze.

Slavoj Žižek (Slovenia/Yugoslavia, 1949- )
Known for: Freudo-Marxism. Ljubljana school of psychoanalysis. Lacanian psychoanalysis. Hegelianism. Dialectical materialism. Ideology as unconscious fantasy. False consciousness.
Works: The Sublime Object of Ideology (1989). The Abyss of Freedom (1997). On Belief (2001). Welcome to the Desert of the Real (2002). Organs without Bodies (2003). The Parallax View (2006). Living in the End Times (2010). Less Than Nothing: Hegel and the Shadow of Dialectical Materialism (2012). Absolute Recoil: Towards a New Foundation of Dialectical Materialism (2014).

An undated photograph of Slavoj Žižek.

On 3 lists
(Zarathustra) (Persia/Iran, c. 1200-900 – 1133-833 BCE)
Known for: Zoroastrianism. Manicaeism. Mithraism. Ahmadiyya. Struggle between aša and druj. Mazda-Yasna ethics.
Works: Gathas. Avesta.

Zoroaster (with globe) in detail from Raphael’s The School of Athens (1509).

Thales of Miletus (Ancient Greece, c. 624-546 BCE)
Known for: Empiricism. Naturalism. Monism. Water as arche (universal substance and originating principle of nature). Thales’ theorem. Intercept theorem. Use of deductive reasoning in geometry.
Works: Discussed by Herodotus and Aristotle. Lives of Eminent Philosophers (by Diogenes Laërtius) (c. 250 CE).

This marble bust of Thales of Miletus, made during the Roman Empire, is now located at the Capitoline Museums in Rome.

Kanada (India, c. 600-500 BCE (?))
Known for: Hinduism. Vaisheshika school. Atomism. Realism. Six padārthas: dravya (substance), guna (quality), karman (motion), samanya (universal), visesa (particular), and samavaya (inherence).
Works: Vaisheshka Sutra (Kanada Sutras).

An artist’s imagining of Kanada.

Mahavira (Vardhamana) (India, 599/497–527/425 BCE)
Known for: Jainism. Doctrine of non-injury applies to all living beings. Anekantavada (many-sided reality). Syadvada (all judgments are conditional). Nayavada. Five vows: ahimsa (non-injury); satya (truthfulness); asteya (non-stealing); brahmacharya (chastity); aparigraha (non-attachment).
Works: Jain Agamas (attrib.) Samavayanga Sutra. Acharanga Sutra.
A statue of Mahavira. It may be from a 16th Century Jain temple in the Dilwara complex of temples at Mount Abu, in Rajasthan, India.

Diogenes the Cynic (Ancient Greece, c. 412-323 BCE)
Known for: Cynicism. Solvitur ambulando. “Cosmopolitan.” Praise of dogs.
Works: Lives and Opinions of Eminent Philosophers (by Diogenes Laërtius) (c. 250 CE).

Diogenes Sitting in His Tub is an 1860 painting by Jean-Léon Gérôme. It is now in the Walters Art Museum in Baltimore, Maryland.

Chanakya  (Kauṭilya; Vishnugupta) (India, c. 350–275 BCE)
Known for: Political science. Economics. Four necessary fields of knowledge: (1) the Vedas, the Anvikshaki (philosophy of Samkhya, Yoga and Lokayata); (3) political science; (4) economics (Varta of agriculture, cattle and trade). Raja-rishi (sage-king).
Works: Arthashastra (attrib). Chanakya Niti (attrib.)

An artist’s imagining of Chanakya.

Zeno of Citium (Zeno the Stoic) (Ancient Greece, c. 334-262 BCE)
Known for: Stoicism. Three branches of philosophy: physics, ethics, logic. Rationality of human nature. Virtue ethics. World citizenship. Happiness occurs when right reason coincides with universal reason (Logos).
Works: Zeno’s Republic (lost). Lives and Opinions of Eminent Philosophers (by Diogenes Laërtius) (c. 250 CE).

A marble bust of Zeno of Citium located in the Capitoline Museums in Rome.

Xun Kuang (Xunzi) (China, c. 313–238 BCE)
Known for: Confucianism. Human nature is innately evil and is rectified by ethical norms. The way changes with the times. Gentleman king (junzi), aided by a class of erudites (ru).
Works: The Xunzi.

An artist’s imagining of Xun Kuang.

Han Fei (Han Feizi) (China, c. 280-233 BCE)
Known for: Legalism. Human nature is driven by self-interest. Government should use self-interest to steer citizens, using reward and punishment. Possession of authority brings the right to obedience. Rulers should not rule arbitrarily but should promulgate laws that all must obey. Ruler must use statecraft (shu) to govern. Governments should adapt to the changing circumstances of the people.
Works: The Han Feizi (attrib.).

An undated portrait of Han Fei.

Cicero (Marcus Tullius Cicero) (Roman Republic, 106-43 BCE)
Known for: Stoicism. Eclecticism. Peripateticism.
Works: De Oratore (On the Orator) (55 BCE). De Re Publica (On the Commonwealth) (51 BCE). Paradoxa Stoicorum (Stoic Paradoxes) (46 BCE). De Natura Deorum (On the Nature of the Gods) (45 BCE). Tusculanae Disputationes (45 BCE). De Finibus Bonorum et Malorum (On the Ends of Good and Evil) (45 BCE). De Officiis (On Duties) (44 BCE). De Legibus (On the Laws).

This marble bust of Cicero dating to the 1st Century BCE is located in the Capitoline Museums in Rome.

Lucretius (Titus Lucretius Carus) (Roman Republic, c. 99-55 BCE)
Known for: Epicureanism. Atomism.
Works: De Rerum Natura (On the Nature of Things) (c. 55 BCE).

An engraving showing a marble bust of Lucretius.

Sextus Empiricus (Roman Empire, c. 160-210 CE)
Known for: Pyrrhonism. Skepticism. Empiric school.
Works: Outlines of Pyrrhonism. Against the Mathematicians (two versions).
This marble bust has been identified by some as Sextus Empiricus and by others as Ancient Greek playwright Euripides.

Vasubandhu (India, c. 300-400 CE)
Known for: Buddhism. Mahayana Buddhism. Yogacara. Appearance only (vijñapti-mātra). Sautrāntika. Kṣanikavāda. Storehouse consciousness (ālayavijñāna). Logico-epistemology.
Works: Abhidharmakośakārikā (Commentary on the Treasury of the Abhidharma). Vimśatikāvijñaptimātratāsiddhi (Twenty Verses on Representation Only). Triṃśikā-vijñaptimātratā (Thirty Verses on Representation-only). Trisvabhāvanirdeśa (Three Natures Exposition). A Method for Argumentation (Vada-vihi).

An undated drawing of Vasubandhu.

Hypatia of Alexandria (Egypt/Roman Empire, c. 350/370-415 CE)
Known for: Neoplatonism.
Works: Commentary on Diophantus’s Arithmetica.

A still image from the 2009 historical drama Agora, a film directed by Alejandro Amenábar. In the film, actress Rachel Weisz plays Hypatia of Alexandria.

Hōnen (Japan, 1133–1212)
Known for: Buddhism. Jōdo-shū (Pure Land Buddhism). Membutsu. Shichikajō-kishōmon (Seven Article Pledge).
Works: Senchaku Hongan Nembutsushū (1198). One-Sheet Document (1212).
A 12th Century portrait of Honen by Fujiwqara Takanobu.

Shinran (Japan, 1173–1261)
Known for: Buddhism. Jōdo Shinshū (school of Pure Land Buddhism). Primacy of faith over practice. Shinjitsu no shinjin (true faith).
Works: Kyogyoshinsho (1224).

This 15-foot-tall bronze statue of Shinran stood in front of a Buddhist temple in Hiroshima, Japan in 1945, when the atomic bomb was dropped on that city. The statue was transplanted to New York City in 1955 and it now stands in front of the New York Buddhist Temple on Riverside Drive.

Dōgen (Dōgen Zenji) (Japan, 1200–1253)
Known for: Zen Buddhism. Sōtō school. Buddha-nature (Busshō). Time-Being (Uji). Perfect expression (Dōtoku). Zazen. Shikantaza. Oneness of practice-enlightenment.
Works: Bendōwa (A Talk on the Endeavor of the Path) (1231). Shōbōgenzō (Eihei Kōroku) (1231-1253). Eihei Shingi. Shinji Shōbōgenzō.

A portrait of Dogen.

Madhvacharya (Purna Prajña; Ananda Teertha) (India, 1238–1317)
Known for: Hinduism. Dvaita Vedanta. Dualism (distinction between Atman and Brahman). Three pramāna (correct means of knowledge): (1) pratyaksha (perception); (2) anumāna (inference); (3) śabda (expert teaching). Kevala-pramana. Two types of tattvas (realities): (1) svatantra tattva (independent reality; (2) asvatantra tattva (dependent reality). “Atat tvam asi” (Thou art not That). Founded Udupi Sri Krishna Matha.
Works: Sarvamula Granthas (including the Anuvyakhyana).

An artist’s imagining of Madhvacharya.

Erasmus (Desiderius Erasmus Roterodamus) (Netherlands, 1466-1536)
Known for: Humanism. Via Media. Free will. Counter-Reformation.
Works: Handbook of a Christian Knight (1503). The Praise of Folly (1511). Copia: Foundations of the Abundant Style (1512). Julius Excluded from Heaven (1514). Sileni Alcibiadis (1515). Education of a Christian Prince (1516). De libero arbitrio diatribe sive collatio (The Freedom of the Will) (1524). Explanation of the Apostles’ Creed (1533).

This 1524 portrait of Erasmus by Hans Holbein the Younger is now in the National Gallery in London.

Thomas More (England, 1478-1535)
Known for: Humanism. Roman Catholicism. Utilitarianism. Euthanasia.
Works: Utopia (1516). The Answer to Luther (1523). A Dialogue Concerning Heresies (1530). The Confutation of Tyndale’s Answer (1532-1533). Apology (1533).

This 1527 portrait of Sir Thomas More by Hans Holbein the Younger is now in the Frick Collection in New York.

Johann Gottlieb Fichte (Germany, 1762-1814)
Known for: Idealism. Romanticism. Post-Kantian transcendental idealism. Nationalism. The absolute consciousness. Mutual recognition. The principle of reciprocal determination. The primacy of the practical. Original drive (Urtrieb). Thesis-antithesis-synthesis. Self-consciousness as a social phenomenon.
Works: An Attempt at a Critique of All Revelation (1792). The Vocation of the Scholar (1794. Foundations of the Science of Knowledge (1794-1795). Foundations of Natural Right (1797). Foundations of Transcendental Philosophy (1796-1799). The Vocation of Man (1800). The Science of Knowing (1804). On the Nature of the Scholar (1806). Addresses to the German Nation (1808).

An engraving of Johann Gottlieb Fichte made by Johann Friedrich Jugel and based on an 1808 portrait of Fichte by Heinrich Anton Dähling.

Friedrich Schelling (Germany, 1775-1854)
Known for: Idealism. Romanticism. Naturphilosophie. “Absolute idealism.” Philosophy of identity. Positive philosophy. “Unconscious infinity.”
Works: “New Deduction of Natural Law” (1797). Ideas Concerning a Philosophy of Nature (1797). On the World-Soul (1798). System of Transcendental Idealism (1800). “Presentation of My System of Philosophy” (1801). Philosophical Inquiries into the Essence of Human Freedom (1809). Introduction to the Philosophy of Mythology (1856). Philosophy of Mythology (1857). Philosophy of Revelation (1858).

This 1835 portrait of Friedrich Schelling by Joseph Karl Stieler is now in the Neue Pinakothek in Munich, Germany.

Herbert Spencer (UK, 1820-1903)
Known for: Positivism. Classical liberalism. Social Darwinism. Laissez-faire. Utilitarianism. “Surivival of the fittest.” School of Synthetic Philosophy.
Works: “On the Proper Sphere of Government” (1842). Social Statics, or, The Conditions Essential to Human Happiness Specified, and the First of Them Developed (1851). “The Philosophy of Style” (1852). “Progress: Its Law and Cause” (1857). First Principles of a New System of Philosophy (1862). Principles of Biology (1864). The Man Versus the State (1884). The Principles of Ethics (1879-1897).

An undated photograph of Herbert Spencer.

Sigmund Freud (Austria, 1856-1939)
Known for: Psychoanalysis. Free association. Transference. Oedipus complex. Id, ego and super-ego. Repression. Unconscious. Seduction theory. Oral, anal and phallic phases.
Works: Studies on Hysteria (with Josef Breuer) (1895). The Interpretation of Dreams (1899). The Psychopathology of Everyday Life (1901). Jokes and their Relation to the Unconscious (1905). Three Essays on the Theory of Sexuality (1905). Totem and Taboo (1913). “The History of the Psychoanalytic Movement” (1914). “Mourning and Melancholia” (1917). “Beyond the Pleasure Principle” (1920). Group Psychology and the Analysis of the Ego (1921). The Ego and the Id (1923). The Future of an Illusion (1927). Civilization and its Discontents (1930). Moses and Monotheism (1937).

A photograph of Sigmund Freud from about 1900.

George Santayana (Jorge Agustín Nicolás Ruiz de Santayana y Borrás) (Spain/US/Italy, 1863-1952)
Known for: Pragmatism. Naturalism. Epiphenomenalism. Materialism. Skepticism. Natural aristocracy.
Works: The Sense of Beauty (1896). The Life of Reason: The Phases of Human Progress (1905-1906). Skepticism and Animal Faith (1923). The Realms of Being (1942).

An undated photograph of George Santayana.

Sun Yat-sen (Sun Wen; Sun Deming) (China, 1866–1925)
Known for: Three Principles of the People (nationalism, democracy, welfare).
Works: The Outline of National Reconstruction (1918). The Fundamentals of National Reconstruction (1924). The Principle of Nationalism (1953).

An undated tinted photograph of Sun Yat-sen.

Mohandas K. Gandhi (Mahatma Gandhi) (India, 1869-1948)
Known for: Nonviolent civil disobedience (ahisma). Satyagraha. Brahmacharya. Swaraj (self-rule). Sarvodaya.
Works: Hind Swaraj, or Indian Home Rule (1909). The Story of My Experiments with Truth (1925-1928).

A 1946 photograph of Gandhi with his spinning wheel by Margaret Bourke-White

Nishida Kitaro (Japan, 1870–1945)
Known for: Kyoto School. Non-dualistic concrete logic (logic of basho). Absolute Nothingness.
Works: An Inquiry into the Good (1911). Thinking and Experience (1915). Intuition and Reflection in Self-Consciousness (1913-1917). The Problem of Consciousness (1918-1919). Art and Morality (1920-1923). (1923–27). From the Acting to the Seeing (1923-1927). The System of Universals in Self-Awareness (1928-1929). The Self-Awareness and Determination of the Nothingness (1930-1932). Fundamental Problems of Philosophy (World of Act) (1933). Fundamental Problems of Philosophy Continued (World as Dialectic) (1934). “The Logic of the Place of Nothingness and the Religious Worldview” (1945).

An undated photograph of Nishida Kitaro.

Ramana Maharshi (India, 1879–1950)
Known for: Hinduism. Advaita Vedanta. Self-enquiry (vichara). Bhaki (devotion). Self as sat-chit-anada (being-consciousness-bliss).
Works: Nān Yār? (Who am I?) (1902, pub. 1923). Five Hymns to Arunachala (1914). Forty Verses on Reality (1928). Five Verses on the Self (1947).

An undated photograph of Ramana Maharshi.

Hans-Georg Gadamer (Germany, 1900-2002)
Known for: Ontological hermeneutics. Hermeneutic phenomenology. Practical philosophy. “All products of a tradition stand within that tradition.” Fusion of horizons. Language is the unity of the infinite and finite. Consciousness is historically-effected.
Works: Truth and Method (1960). The Idea of the Good in Platonic-Aristotelian Philosophy (1978). Reason in the Age of Science (1981). Dialogue and Dialectic: Eight Hermeneutical Studies on Plato (1934-1974, pub. 1983). The Enigma of Health: The Art of Healing in a Scientific Age (1993).

An undated photograph of Hans-Georg Gadamer.

Ayn Rand (Russia/US, 1905-1982)
Known for: Objectivism. Rational/ethical egoism. Laissez-faire capitalism.
Works: We the Living (1936). Anthem (1938). The Fountainhead (1943). Atlas Shrugged (1957). For the New Intellectual (1961). The Virtue of Selfishness (1964). Capitalism: The Unknown Ideal (1966). Introduction to Objectivist Epistemology (1979). Philosophy: Who Needs It (1982).

An undated photograph of Ayn Rand.

Claude Lévi-Strauss (France, 1908-2009)
Known for: Structuralism. Structural anthropology. Culinary triangle. Bricolage. Mytheme. Alliance theory.
Works: The Elementary Structures of Kinship (1949). Tristes Tropiques (1955). Structural Anthropology (1958). The Savage Mind (1962). Mythologies (1964-1971). Myth and Meaning (1978).

An undated photograph of Claude Lévi-Strauss.

Simone Weil (France, 1909-1943)
Known for: Modern Platonism. Decreation. The need for roots. Patriotism of compassion. Unjust character of affliction. Metaxu. Methodical thinking. Attention. Reading.
Works: “Science and Perception in Descartes” (1929-1930). “Capital and the Worker” (1932). “Prospects: Are We Heading for the Proletarian Revolution?” (1933). “Reflections concerning Technology, National Socialism, the U.S.S.R., and certain other matters” (1933) “Reflections Concerning the Causes of Liberty and Social Oppression” (1934). “Let Us Not Start Another Trojan War” (“The Power of Words”) (1936). “The Iliad or the Poem of Force” (1940). “The Pythagorean Theorem” (1941). “Essay on the Concept of Reading” (1941). “Reflections on the Right use of School Studies with a View to the Love of God” (1942). “La Personne et le sacré” (“Human Personality”) (1942–1943). “Draft for a Statement of Human Obligations” (1943). The Need for Roots (1943, pub. 1949).  Gravity and Grace (1947). Lectures on Philosophy (pub. 1978).

A photograph of Simone Weil from c. 1921.

Donald Davidson (US, 1917-2003)
Known for: Analytic philosophy. Radical interpretation. Anomalous monism. Truth-conditional semantics. Principle of charity. Reasons as causes. Understanding as translation. Rejection of the third dogma of empiricism.
Works: “Actions, Reasons, and Causes” (1963).  “Truth and Meaning” (1967). “Causal Relations” (1967). “On Saying That” (1968). “The Individuation of Events” (1969). “True to the Facts” (1969). “Mental Events” (1970). “How Is Weakness of the Will Possible?” (1970). “Agency” (1971). “Radical Interpretation” (1973). “On the Very Idea of a Conceptual Scheme” (1974). “Thought and Talk” (1975). “The Method of Truth in Metaphysics” (1977). “Intending” (1978). “What Metaphors Mean” (1978). “Quotation” (1979). “Rational Animals” (1982). “A Coherence Theory of Truth and Knowledge” (1983). “First-Person Authority” (1984). “Adverbs of Action” (1985). “A Nice Derangement of Epitaphs” (1986). “Knowing One’s Own Mind” (1987). “Three Varieties of Knowledge” (1991). “Laws and Cause” (1995). Essays on Actions and Events (2001). Truth and Predication (2005).
A 1990 photograph of Donald Davidson by Steve Pyke.

G.E.M. Anscombe (Elizabeth Anscombe) UK, 1919-2001)
Known for: Analytic philosophy. Brute facts. “Under a description.” Direction of fit. Consequentialism.
Works: Intention (1957). “Modern Moral Philosophy” (1958). Causality and Determination (1971). “The First Person” (1975). Times, Beginnings and Causes (1975). From Parmenides to Wittgenstein (1981). Metaphysics and the Philosophy of Mind (1981). Ethics, Religion and Politics (1981). Human Life, Action and Ethics (pub. 2005).

An undated photograph of G.E.M. Anscombe.

Thomas Kuhn (US, 1922-1996)
Known for: Analytic philosophy. Historical turn. Paradigm shift. Incommensurability. Normal science. Kuhn loss.
Works: The Copernican Revolution: Planetary Astronomy in the Development of Western Thought (1957). “The Function of Measurement in Modern Physical Science” (1961). The Structure of Scientific Revolutions (1962). “The Function of Dogma in Scientific Research” (1963). “Logic of Discovery or Psychology of Research?” (1970). The Essential Tension: Selected Studies in Scientific Tradition and Change (1977). “Objectivity, Value Judgment, and Theory Choice” (1977). “Metaphor in Science” (1979). “Rationality and Theory Choice” (1983). Black-Body Theory and the Quantum Discontinuity, 1894-1912 (1987). “The Trouble with the Historical Philosophy of Science” (1992). The Road Since Structure: Philosophical Essays, 1970-1993 (2000).

An undated photograph of Thomas Kuhn by Bill PierceTime Life Pictures/Getty Images.

Judith Jarvis Thomson (US, 1929- )
Known for: Analytic philosophy. The violinist argument. Moral objectivity.
Works: “A Defense of Abortion” (1971). “The Trolley Problem” (1985). Rights, Restitution and Risk (1986). “Goodness and Utilitarianism” (1993). The Realm of Rights (1992). Moral Relativism and Moral Objectivity (with Gilbert Harman) (1996). Goodness and Advice (2001).

A 2010 photograph of Judith Jarvis Thomson by Steve Pyke.

Luce Irigaray (Belgium/France, 1930- )
Known for: Feminism. “Women on the market.”
Works: Speculum of the Other Woman (1974). This Sex Which Is Not One (1977). Elemental Passions (1982). Belief Itself (1983). An Ethics of Sexual Difference (1984). To Speak Is Never Neutral (1985). Sexes and Genealogies (1987). Je, tu, nous: Towards a Culture of Difference (1990). To Be Two (1997). Between East and West: From Singularity to Community (1999).
An undated photograph of Luce Irigaray.

Amartya Sen (India, 1933- )
Known for: Capability approach. Welfare economics. Social choice theory. Nobel Prize in Economics (1998).
Works: Collective Choice and Social Welfare (1970). Poverty and Famines: An Essay on Entitlement and Deprivation (1981). Choice, Welfare, and Measurement (1983). Commodities and Capabilities (1985). Inequality Reexamined (1992). Development as Freedom (1999). The Idea of Justice (2009).

A photograph of Amartya Sen from c. 1998.

Thomas Nagel (Yugoslavia/US, 1937- )
Known for: Analytic philosophy. Rationalism. Radical skepticism. Practical reasoning. Individualism.
Works: The Possibility of Altruism (1970). “What Is It Like to Be a Bat?” (1974). Mortal Questions (1979). The View from Nowhere (1986). What Does It All Mean?: A Very Short Introduction to Philosophy (1987). Equality and Partiality (1991). The Last Word (1997). Other Minds (1999). Concealment and Exposure (2002). Mind and Cosmos (2012).
A 1978 photograph of Thomas Nagel.

Robert Nozick (US, 1938-2002)
Known for: Analytic philosophy. Libertarianism. Utility monster. Experience machine. Lockean proviso. Paradox of deontology. Entitlement theory. Deductive closure. Four conditions on knowledge.
Works: Anarchy, State, and Utopia (1974). Philosophical Explanations (1981). The Examined Life (1989). The Nature of Rationality (1993). Socratic Puzzles (1997). Invariances: The Structure of the Objective World (2001).

An undated photograph of Robert Nozick.

John McDowell (South Africa/UK/US, 1942- )
Known for: Analytic philosophy. Therapeutic philosophy. Perceptual content is conceptual “all the way down.”
Works: Mind and World (1994). Mind, Value, and Reality (1998). Meaning, Knowledge, and Reality (1998). Having the World in View: Essays on Kant, Hegel, and Sellars (2009). The Engaged Intellect: Philosophical Essays (2009).

An undated photograph of John McDowell.

Martha Nussbaum (US, 1947- )
Known for: Analytic philosophy. Capability approach. Feminism. Multiculturalism.
Works: The Fragility of Goodness (1986). Sex and Social Justice (1998). Hiding from Humanity: Disgust, Shame, and the Law (2004). Frontiers of Justice: Disability, Nationality, Species Membership (2006). From Disgust to Humanity: Sexual Orientation and Constitutional Law (2010).

A 2008 photograph of Martha Nussbaum.

Cornel West (US, 1953- )
Known for: Neopragmatism. Existentialism. Africana philosophy. Historicism.
Works: Prophetic Fragments (1988). The American Evasion of Philosophy: A Geneology of Pragmatism (1989). The Ethical Dimensions of Marxist Thought (1991). Prophetic Thought in Postmodern Times: Beyond Eurocentrism and Multiculturalism (1993). Race Matters (1994). Democracy Matters (2004). The Rich and the Rest of Us: A Poverty Manifesto (with Tavis Smiley) (2012).

An undated photograph of Cornel West.