Plato's dialogues were part of a body of fourth-century literature in which Socrates questioned (and usually got the better of) friends, associates, and supposed experts. A. G. Long considers how Plato explained the conversational character of Socratic philosophy, and how Plato came to credit first Socrates and then, more generally, the philosopher with an alternative to conversation--internal dialogue or self-questioning. Conversation and self-sufficiency...