Recent scholarship on the nature of Socratic practice has ascribed much significance to the so-called ‘sincerity’ rule, that Socrates’ interlocutors must only assert or assent to what they really believe. I argue that conventional interpretations of this rule tacitly attribute to Plato’s Socrates on the basis of meagre evidence a ‘Cartesian’ picture of self-knowledge belied by much counterevidence in the dialogues. I develop a set of analogies between Socratic methods and modern pedagogical, psychoanalytic, and forensic practice and argue that the Socratic demand for sincerity is not best understood as a demand to assert only pre-existing beliefs. It is, rather, a demand to engage in good faith in an effort at articulating mental content and giving it linguistic expression in a form for which one is prepared to take responsibility. The ethical value of this exercise consists in its simulating, and thereby preparing the interlocutor for, the conditions of public life.