Theaetetus is a seminal text in the philosophy of knowledge and is acknowledged as one of Plato's finest works. Cast as a conversation between Socrates and a clever but modest student, Theaetetus, it explores one of the key issues in philosophy: what is knowledge? Though no definite answer is reached, the discussion is penetrating and wide-ranging, covering the claims of perception to be knowledge, the theory that all is in motion, and the perennially tempting idea that knowledge and truth are relative to different individuals or states.