Θεαίτητος

A dialogue on the nature of knowledge, staged as a conversation between Socrates, the mathematician Theodorus of Cyrene, and Theodorus's student Theaetetus. Socrates tests and ultimately rejects three definitions of knowledge in turn: knowledge as perception, as true judgment, and as true judgment accompanied by an account.

Written in Plato's later period, the dialogue is aporetic — it ends without settling on a definition, leaving the participants (and the reader) aware of how little is actually understood about knowledge itself. It is regarded as one of the founding texts of epistemology and is notable for its careful, patient argumentative structure.