Abelard, Peter (1079-1142) French philosopher. One of the most influential medieval logicians and theologians. Around 1113, while teaching theology in Paris, Abelard fell in love with his student Heloise, whom he secretly married; he was condemned for heresy a few years later because of his nominalist views. He wrote Sic et Non.
Anaxagoras (c. 500-428 B.C.) Greek pre-Socratic philosopher who is said to have made Athens the center of philosophy and to have been Socrates' teacher; he rejected the four elements theory of Empedocles and posited instead an infinite number of unique particles of which all objects are composed.
Anaximander (c. 611-547 B.C.) Greek pre-Socratic thinker who believed the universal substance to be "the boundless" or "the indefinite," rather than something resembling familiar objects. Unlike Thales (his teacher) and Anaximenes, he did not believe that a single element underlies all things.
Anaximenes (6th century B.C.) One of the pre-Socratics and an associate of Anaximander. He agreed with Thales that one type of substance underlies the diversity of observable things. Anaximenes believed that air was that universal substance and that all things are made of air in different degrees of density.
Anselm, St. (1033-1109) Italian monk and Scholastic theologian who became archbishop of Canterbury. St. Anselm founded Scholasticism, integrated Aristotelian logic into theology, and believed that reason and revelation are compatible. He is most famous for his influential ontological argument for God's existence.
Aquinas, St. Thomas (1225-74) The greatest thinker of the Scholastic School. His ideas, in 1879, made the official Catholic philosophy. He incorporated Greek ideas into Christianity by showing Aristotle's thought to be compatible with church doctrine. In his system, reason and faith (revelation) form two separate but harmonious realms whose truths complement rather than oppose one another. He presented influential philosophical proofs for the existence of God. His works include Summa Theologica and On Being and Essence .
Aristotle (384-322 B.C.) Greek philosopher, scientist, logician, and student of many disciplines. Aristotle studied under Plato and became the tutor of Alexander the Great. In 335 he opened the Lyceum, a major philosophical and scientific school in Athens. Aristotle emphasized the observation of nature and analyzed all things in terms of "the four causes." In ethics, he stressed that virtue is a mean between extremes and that man's highest goal should be the use of his intellect. Most of Aristotle's works were lost to Christian civilization from the fifth through the twelfth centuries. Among his writings are Metaphysics , Politics , and Rhetoric .
Augustine of Hippo, St. (354-430) The greatest of the Latin church fathers and possibly the most influential Christian thinker after St. Paul. St. Augustine emphasized man's need for grace. His Confessions and The City of God were influential.
Averroes (1126-98) Spanish-born Arabian philosopher, lawyer, and physician whose detailed commentaries on Aristotle were influential for over 300 years. He emphasized the compatibility of faith and reason but believed philosophical knowledge to be derived from reason. The church condemned his views.
Avicenna (980-1037) Islamic medieval philosopher born in Persia. His Neoplatoist interpretation of Aristotle greatly influenced medieval philosophers, including St. Thomas Aquinas. Avicenna was also a physician; his writings on medicine were important for nearly 500 years.
Bacon, Sir Francis (1561-1626) English statesman, essayist, and philosopher, one of the great precursors of the tradition of British empiricism and of belief in the importance of scientific method. He emphasized the use of inductive reasoning in the pursuit of knowledge.
Bentham, Jeremy (1748-1832) English philosopher, and one of the founders of utilitarianism. Bentham was a highly influential reformer of the British legal, judicial, and prison system. He is the author of Introduction to the Principles of Morals and Legislation .
Berkeley, George (1685-1753) Irish philosopher and an Anglican bishop, one of the British empiricists. Berkeley held to a "subjective idealism." He believed that everything that exists is dependent on being perceived by a mind. According to this view, material objects are simply collections of "ideas" in the mind of a person or of God. His works include Essay Toward a New Theory of Vision and A Treatise Concerning the Principles of Human Knowledge .
Boethius (c. 475-535) Roman statesman, philosopher, and translator of Aristotle, whose Consolation of Philosophy (written in prison) was widely read throughout the Middle Ages; it showed reason's role in the face of misfortune and was the link between the ancient philosophers and the Scholastics.
Buber, Martin (1878-1965) German-Israeli philosopher influenced by Jewish mysticism and existentialism, a major force in twentieth-century Jewish thought and philosophy of religion. His I and Thou held that God and man can have a direct and mutual "dialogue."
Comte, Auguste (1798-1857) French founder of positivism and social reformer. Comte put forth a "religion of humanity" that replaced the notion of God with the notion of humankind as a whole. He invented the term sociology .
Democritus (c. 460-370 B.C.) Greek philosopher who proposed a mechanistic theory of the world that required no supernatural forces, only the constant motion of the indestructible atoms of which everything is composed. He held that perception is an unreliable source of knowledge and knowledge can be obtained through reason only.
Descartes, Rene (1596-1650) French philosopher and scientist, considered the father of modern philosophical inquiry. Descartes tried to extend mathematical method to all knowledge in his search for certainty. Discarding the medieval appeal to authority, he began with "universal doubt," finding that the only thing that could not be doubted was his own thinking. The result was his famous "Cogito, ergo sum, " or "I think, therefore I am." His major works are the Discourse on Method and Meditations .
Dewey, John (1859-1952) Leading American philosopher, psychologist, and educational theorist. Dewey developed the views of Charles S. Peirce (1839 - 1914) and William James into his own version of pragmatism. He emphasized the importance of inquiry in gaining knowledge and attacked the view that knowledge is passive.
Diderot, Denis (1713-84) Materialist thinker of the French Enlightenment and originator of the Encyclopedie .
Diogenes (c. 400- 325 B.C.) Greek founder of cynicism who rejected social conventions and supposedly lived in a tub in defiance of conventional comforts.
Empedocles (c. 495-435 B.C.) Greek pre-Socratic philosopher who believed the universe to consist of the four elements, air, fire, water, and earth. Empedocles held that the interaction between love and hate causes the mixing of the elements.
Engels, Friedrich (1820-95) German socialist thinker and historian, and the cofounder of Marxism; Marx's lifelong collaborator and coauthor of the Communist Manifesto ; and an originator of the philosophy of dialectical materialism.
Epictetus (c. 50-138) Stoic moral philosopher who established a school of philosophy after being freed as a slave. His Manual teaches that only by detaching ourselves from what is not in our power can we attain freedom.
Epicurus (341-270 B.C.) Founder of the Epicurean philosophy and a follower of Democritus, founder of atomism. Virtually all of Epicurus's writings are lost.
Hegel, Georg Wilhelm Friedrich (1770-1831) German philosopher whose idealistic system of metaphysics was highly influential; it was based on a concept of the world as a single organism developing by its own inner logic through trios of stages called "thesis, antithesis, and synthesis" and gradually coming to embody reason. Hegel held the monarchy to be the highest development of the state. His works include Logic and Phenomenology of Mind .
Heidegger, Martin (1889-1976) German philosopher who studied with Husserl. Heidegger's own philosophy, which was influenced by Kierkegaard, emphasized the need to understand "being," especially the unique ways that humans act in and relate to the world. He wrote Being and Time .
Heraclitus (c. 535-475 B.C.) Pre-Socratic philosopher opposed to the idea of a single ultimate reality. Heraclitus believed that all things are in a constant state of change.
Hobbes, Thomas (1588-1679) English materialist and empiricist, one of the founders of modern political philosophy. In the Leviathan, Hobbes argued that because men are selfish by nature, a powerful absolute rules is necessary. In a "social contract," men agree to give up many personal liberties and accept such rule.
Hume, David (1711-76) British empiricist whose arguments against the proofs for God's existence are still influential. In his Treatise of Human Nature, Hume held that moral beliefs have no basis in reason, but are based solely on custom.
Husserl, Edmund (1859-1938) German philosopher who founded the phenomenology movement. He aimed at a completely accurate description of consciousness and conscious experience. His works include Logical Investigations and Ideas for a Pure Phenomenology .
James, William (1842-1910) American philosopher and psychologist, one of the founders of pragmatism, and one of the most influential thinkers of his era. James viewed consciousness as actively shaping reality, defined truth as "the expedient" way of thinking, and held that ideas are tools for guiding our future actions rather than reproductions of our past experiences. His writings include The Will to Believe and Pragmatism .
Kant, Immanuel (1724-1804) German philosopher, possibly the most influential of modern times. He synthesized Leibniz's rationalism and Hume's skepticism into his "critical philosophy": in The Critique of Pure Reason , he wrote that ideas do not conform to the external world, but rather the world can be known only insofar as it conforms to the mind's own structure. In The Critique of Practical Reason , Kant claimed that morality requires a belief in God, freedom, and immortality, although these can be proved neither scientifically nor by metaphysics. Finally, in his Metaphysic of Morals , he presented the concept of the categorical imperative.
Kierkegaard, Søren (1813-55) Danish philosopher, religious thinker, and extraordinarily influential founder of existentialism. Kierkegaard held that "truth is subjectivity," that religion is an individual matter, and that man's relationship to God requires suffering. He wrote Either/Or and Fear and Trembling .
Leibniz, Gottfried Wilhelm (1646-1716) German philosopher, diplomat, and mathematician, one of the great minds of all time. Leibniz was an inventor (with Sir Isaac Newton) of the calculus and a forefather of modern mathematical logic. He held that the entire universe is one large system expressing God's plan. His writings include New Essays on Human Understanding .
Locke (1632-1704) Influential Founder of Brtish empiricism. In his Essay Concerning Human Understanding , Locke wrote that all ideas come to mind from experience and that none are innate. He also held that authority derives solely from the consent of the governed, a view that deeply influenced the American Revolution and the writing of the U.S. Constitution. His two Treatises on Government express his political thought.
Lucretius (c. 99-55 B.C.) Roman Epicurean philosopher and poet. In De Rerum Natura (On the Nature of Things), Lucretius depicted the entire world, including the soul, as composed of atoms.
Machiavelli, Niccolo (1469-1527) Italian Renaissance statesman and political writer. In The Prince , one of the most influential political books of modern times, Machiavelli argues that any act of a ruler designed to gain and hold power is permissible. The term Machiavellian is used to refer to any political tactics that are cunning and power-oriented.
Maimonides (1135-1204) Spanish-born medieval Jewish philosopher and thinker. Maimonides tried to synthesize Aristotelian and Judaic thought. His works, such as Guide to the Perplexed , had enormous influence on Jewish and Christian thought.
Marcus Aurelius (121-180) Roman emperor from A.D. 161, and a proponent of the Stoic philosophy. His Meditations held that death is as natural as birth and that the world is rational and orderly. Although a great humanitarian, Marcus Aurelius persecuted the Christians of his time.
Marx, Karl (1818-83) German revolutionary thinker, social philosopher, and economist. His ideas, formulated with Engels, laid the foundation for nineteenth-century socialism and twentieth-century communism. Although Marx was initially influenced by Hegel, he soon rejected Hegel's idealism in favor of materialism. His Communist Manifesto and Das Kapitalare among the most important writings of the last 200 years.
Mill, John Stuart (1806-73) English empiricist philosopher, logician, economist, and social reformer. His System of Logic described the basic rules for all scientific reasoning. As a student of Jeremy Bentham, he elaborated on utilitarian ethics; in On Liberty , he presented a plea for the sanctity of individual rights against the power of any government.
Montesquieu, Baron de (Charles-Louis de Secondat) (1689-1755) French political philosopher, influenced by Locke. In Spirit of the Laws , Montesquieu put forth the theory of separation of powers that strongly influenced the writing of the U.S. Constitution.
Moore, G. E. (George Edward) (1873-1958) British philosopher who emphasized the "common sense" view of the reality of material objects. In ethics, Moore held that goodness is a quality known directly by moral intuition and that it is a fallacy to try to define it in terms of anything else.
More, Sir Thomas (1478-1535) A leading Renaissance humanist and statesman, Lord Chancellor of England. More was beheaded for refusing to accept the king as head of the church. Influenced by Greek thinking, he believed in social reform and drew a picture of an ideal peaceful state in his Utopia .
Nietzsche, Friedrich Wilhelm (1844-1900) German philosopher, philologist, and poet. As a moralist, he rejected Christian values and championed a "Superman" who would create a new, life-affirming, heroic ethic by his "will to power." His works include Thus Spoke Zarathustra and Beyond Good and Evil .
Parmenides (b. c. 515 B.C.) The founder of Western metaphysics. This pre-Socratic thinker held that "being" is the basic substance and ultimate reality of which all things are composed and that motion, change, time, difference, and reality are illusions of the senses.
Pascal, Blaise (1623-62) French philosopher, mathematician, scientist, and theologian. His posthumous "Pensees" ("Thoughts") argues that reason is by itself inadequate for man's spiritual needs and cannot bring man to God, who can be known only through mystic understanding.
Plato (c. 428-348 B.C.) Athenian father of Western philosophy and student of Socrates, after whose death he traveled widely. Upon returning to Athens, he founded an academy, where he taught until he died. His writings are in the form of dialogues between Socrates and other Athenians. Many of Plato's views are set forth in The Republic , where an ideal state postulates philosopher kings, specially trained at the highest levels of moral and mathematical knowledge. Plato's other works analyzed moral virtues, the nature of knowledge, and the immortality of the soul. His views on cosmology strongly influenced the next two thousand years of scientific thinking.
Plotinus (205-270) Egyptian-born founder of Neoplatonism, who synthesized the ideas of Plato and other Greek philosophers. Plotinus believed all reality is caused by a series of outpourings (called emanations) from the divine source. Although not himself a Christian, he was a major influence on Christianity.
Pythagoras (c. 582-507 B.C.) Greek philosopher, mathematician, and mystic, founder of a religious brotherhood that believed in the immortality and the transmigration of the soul. Pythagoras may have been the first thinker to assert that numbers constitute the true nature of all things; he also may have coined the term philosophy .
Rousseau, Jean Jacques (1712-78) Swiss-French thinker born in Geneva. Rousseau has been enormously influential in political philosophy, educational theory, and the romantic movement. In The Social Contract (1762), he viewed governments as being expressions of the people's "general will," or rational men's choice for the common good. Rousseau emphasized man's natural goodness.
Russell, Bertrand (1872-1970) English philosopher and logician influential as an agnostic and a pacifist. Early work with Alfred North Whitehead gave birth to modern logic; they coauthored Principia Mathematica . Russell changed his views numerous times but always sought to establish philosophy, especially epistemology, as a science.
Santayana, George (1863-1952) Spanish-born American philosopher and poet; a student of William James. Santayana attempted to reconcile Platonism and materialism, studied how reason works, and found "animal faith," or impulse, to be the basis of reason and belief. Among his works are The Sense of Beauty and The Life of Reason .
Sartre, Jean Paul (1905-80) French philosopher, novelist, and dramatist; one of the founders of existentialism. Sartre was a Marxist through much of his life. He held that man is "condemned to be free" and to bear the responsibility of making free choices. His primary philosophical work was Being and Nothingness .
Schopenhauer, Arthur (1788-1860) German post-Kantian philosopher who held that although irrational will is the driving force in human affairs, it is doomed not to be satisfied. He believed that only art and contemplation could offer escape from determinism and pessimism. Schopenhauer strongly influenced Nietzsche, Freud, Tolstoy, Proust, and Thomas Mann. He wrote The World as Will and Representation .
Scotus, John Duns (c. 1266-1308) Scottish-born Scholastic philosopher who tried to integrate Aristotelian ideas into Christian theology. Scotus emphasized that all things depend not just on God's intellect but on divine will as well. He wrote On the First Principle .
Smith, Adam (1723-1790) Scottish philosopher and economist. The author of The Wealth of Nations , he believed that if government left the marketplace to its own devices, an "invisible hand" would guarantee that the results would benefit the populace. Smith has had enormous influence on economists into the present day.
Socrates (c. 470-399 B.C.) Athenian philosopher who allegedly wrote down none of his views, supposedly from his belief that writing distorts ideas. His chief student, Plato, is the major source of knowledge about his life. Socrates questioned Athenians about their moral, political, and religious beliefs, as depicted in Plato's dialogues; his questioning technique, called dialectic, has greatly influenced Western philosophy. Socrates is alleged to have said that "the unexamined life is not worth living." In 399 B.C., he was brought to trial on charges of corrupting the youth and religious heresy. Sentenced to die, he drank poison.
Spinoza, Benedict (Baruch) (1623-77) Dutch-born philosopher expelled from the Amsterdam Jewish community for heresy in 1656; he was attacked by Christian theologians 14 years later. In Ethics , Spinoza presents his views in a mathematical system of deductive reasoning. A proponent of monism, he held - in contrast to Descartes - that mind and body are aspects of a single substance, which he called God or nature.
Thales of Miletus (c. 636-546 B.C.) Regarded as the first Western philosopher, this pre-Socratic monist thinker is said to have believed that the fundamental principle of all things, or universal substance, is water. All of his writings are lost.
Unamuno, Miguel de (1864-1936) The major Spanish philosophical thinker of his time. Unamuno criticized philosophical abstractions such as "man" for ignoring concrete men. He held that reason by itself is virtually useless and cannot reveal the basic fact of human immortality. He wrote The Tragic Sense of Life in Men and Nations .
Voltaire (Francois Marie Arouet) (1694-1778) French philosopher, essayist, and historian; one of the major thinkers of the Enlightenment. A Deist who was anti-Christian, Voltaire widely advocated tolerance of liberal ideas and called for positive social action. His novel Candide is a parody of the optimism of Leibniz.
Whitehead, Alfred North (1861-1947) British philosopher and mathematician who worked with Bertrand Russell. Whitehead tried to integrate twentieth-century physics into a metaphysics of nature.
William of Ockham (Occam) (c. 1285-1349) Franciscan monk and important English theologian and philosopher. In his nominalism, he opposed much of the thought of St. Thomas Aquinas and of medieval Aristotelianism; he also rejected the pope's power in the secular realm.
Wittgenstein, Ludwig (1889-1951) Austrian-born philosopher who spent the last 20 years of his life in England. Wittgenstein was one of the most influential philosophers of the century, primarily through his emphasis on the importance of the study of language. His Tractatus Logico Philosophicus influenced analytic philosophy. His later views emphasized that philosophic problems are often caused by linguistic confusions.
Zeno of Elea (c. 490-430 B.C.) Pre-Socratic philosopher and disciple of Parmenides. Zeno argued that motion, change, and plurality are logical absurdities and that only an unchanging being is real. His four arguments against motion (Zeno's paradoxes) attempted to demonstrate logically that the notions of time and motion are erroneous.
Zeno (of Citium) the Stoic (c. 334-262 B.C.) Greek philosopher born in Cyprus; the founder of Stoicism.