Derek Parfit is senior research fellow of All Souls College; a regular visiting professor at Harvard, New York University, and Rutgers; and a fellow of both the British Academy and the American Academy of Arts and Sciences.

Born in China and educated in England at the Dragon School and Eton, Parfit took his degree in modern history at Oxford University and later turned to philosophy. He is legendary as a mentor and for his acute monograph-length criticisms of manuscripts, as well as for his important contributions to ethics, practical reasoning, and metaphysics. Parfit is widely regarded as one of the most important contemporary philosophers.

Along with John Rawls's A Theory of Justice, Parfit's magnum opus, Reasons and Persons, helped turn ethics from a moribund and peripheral subject that largely focused on the meanings of moral terms into a vibrant and central philosophical topic. Brimming...