Ralph Cudworth’s theory of mind was the most fully developed philosophical psychology among the Cambridge Platonists. Like his seventeenth-century contemporaries, Cudworth discussed mental powers in terms of soul rather than mind and considered the function of the soul to be not merely intellectual, but vital and moral. Cudworth conceived the soul as a single self-determining unit which combined many powers. He developed this against a philosophical agenda set by Descartes and Hobbes. But he turned to ancient philosophy, especially the philosophy (...) of Plotinus, to develop a psychology which is distinguished by the attention he gives to both conscious and unconscious states, and to the powers which enable it to reflect on itself, to co-ordinate its activities and direct them to good ends. I argue that in so doing, Cudworth sought to elaborate a theory of mind which accounted for observable experience of mental operations. My paper outlines the complexities of Cudworth’s taxonomy of mental powers, focusing on three key powers which Cudworth developed through his reading of Plotinus: energy, self-power, and sympathy. (shrink)