The English philosopher and theologian Ralph Cudworth (1617-1688) was the most important of the Cambridge Platonists, a 17th-century circle which expounded rationalistic theology and ethics.

Ralph Cudworth was born in Aller, Somerset, where his father was rector. His father, who had also been a fellow of Emmanuel College, Cambridge, and chaplain to James I, died in 1624, and Cudworth therefore had his early education from his stepfather, Dr. Stoughton. He entered Emmanuel College in 1632 and received a bachelor of arts degree in 1635, a master of arts degree in 1639, and a bachelor of divinity degree in 1646. In 1645 he was appointed master of Clare College and regius professor of Hebrew. He served as rector of North Cadbury, Somerset, from 1650 to 1654, then returned to Cambridge as master of Christ's College. In 1654 he also married and subsequently had two sons, John and Charles, and a daughter, Damaris (later Lady Masham). His daughter's philosophical writing and her friendship with John Locke helped spread Cudworth's ideas. The rest of his career was at Christ's College; he was involved in the political events of the time and served on and advised parliamentary committees.

Cudworth opposed excessive dogmatism in religion and advocated a predominantly moral conception of Christianity, with latitude in matters of ritual and organization. His earliest public statement of his position was a sermon preached before the House of Commons in 1647 and published later that year.

In A Treatise on Eternal and Immutable Morality Cudworth wrote, "It is universally true that things are what they are not by will but by nature." Thus truth, in morals, religion, and metaphysics, is discoverable by the use of reason. Those who set God's will or the will of a human sovereign above reason--Thomas Hobbes, the nominalists and Calvinists, even the rationalist René Descartes--were Cudworth's targets. Against Hobbes's alleged atheism, materialism, determinism, individualism, and ethical relativism, Cudworth defended theism, dualism, free will, organic political theory, and ethical absolutism.

Cudworth's metaphysical dualism asserts a distinction between active and passive powers, not the Cartesian distinction between thought and extension. Active powers, comprising unconscious "spiritual plastic powers" and deliberative operations, prudential and moral, are teleological. The passive powers are mechanical. In making reason active, Cudworth avoids the usual problems of moral psychology by reaffirming the Socratic identification: to know the good is to love it.

Cudworth's principal philosophical works are The True Intellectual System of the Universe (1678) and A Treatise on Eternal and Immutable Morality (1731). He died on June 26, 1688, and was buried in the chapel of Christ's College.

Further Reading

• For discussions of Cudworth the philosopher see John H. Muirhead, The Platonic Tradition in Anglo-Saxon Philosophy (1931), and Lydia Gysi, Platonism and Cartesianism in the Philosophy of Cudworth (1962). John Arthur Passmore, Ralph Cudworth: An Interpretation (1951), contains the most comprehensive bibliography.
• Cudworth, Ralph, A treatise of freewill and an introduction to Cudworth's treatise, London: Routledge/Thoemmes Press, 1992.