The Philebus is the only Platonic dialogue that takes as its central theme the fundamental Socratic question of the good, understood as that which makes for the best or happiest life. It offers an extended psychological and epistemological investigation of such topics as sensation, memory, desire, anticipation, the truth and falsity of pleasures, and the types and gradations of knowledge, as well as a methodological exposition of dialectic and a metaphysical schema--found nowhere else in the dialogues--that is intended to illuminate the nature of mixture. In its interweaving of ethical, metaphysical, and epistemological issues, the Philebus offers a unique opportunity to assess the relation of these topics in Plato's mature thought and so to gain insight into his philosophical vision as a whole. This edition also includes parallel passages from other Platonic dialogues and related material from Aristotle, the Stoics, and Epicurus.