The most systematic of the Cambridge Platonists, Ralph Cudworth was born at Aller in Somerset, educated at Emmanuel College, Cambridge, elected a fellow of the college in 1639, and appointed master of Clare College in 1645. In these turbulent revolutionary years, he made many enemies, a development that prompted his retirement from the university to become rector of North Cadbury in Somerset in 1650. Four years later, however, he returned to be master of Christ's College. Cudworth's chief work, The True Intellectual System, was published in 1678. It was an important work of scholarship on Greek philosophy as well as a metaphysical system based on theism and a dualist theory of mind. His… theory of "spiritual plastic powers," which he ascribed to all living things, influenced the Encyclopedists. Two important posthumous works by Cudworth, A Treatise Concerning Eternal and Immutable Morality (published in 1731) and A Treatise on Free Will (published in 1838), are directed against both Calvinism and Hobbesian materialism, defending freedom of the will and a rationalist and realist conception of the good.