We continue discussing Book IV of the Republic in Chapter Six, ‘The Republic’s First Question Answered at Last: Personal Justice’. We first attend to Plato’s foray into psychology (literally, his account (logos) of the soul (psuchê)) in which he tries to justify the analogy between city and soul that has shaped the Republic. By appealing to the idea that the same thing cannot simultaneously undergo or perform opposite states or activities (dubbed the Opposition Principle), Socrates argues that the soul has a three-part structure, just as the city does: a rational part, which corresponds to the guardian-rulers in the polis; a spirited part (the seat of anger and pride), which corresponds to the soldierly auxiliaries of the polis; and an appetitive part, which corresponds to the craftspeople. Socrates then derives the personal virtues by applying the political virtues to the soul. The most important personal virtue, of course, is justice, which he conceives of as each part of the soul doing its own work: reason, not appetite or spirit, governs the just soul. We will pay attention to important features of this account, for example how it differs from Cephalus’ and Polemarchus’, for whom justice is a matter of interpersonal, external doing (of how one treats one’s fellows), while for Socrates and Plato is it a matter of intrapersonal, internal being, of what one’s soul is like.