In the Theaetetus, Plato looks afresh at a problem to which, he now realizes, he had earlier given an inadequate answer: the problem of the nature of knowledge. What Plato has to say on this question is of great interest and importance, not only to scholars of Plato, but also to philosophers with wholly contemporary interests. This book is a sustained philosophical analysis and critique of the Theaetetus. David Bostock provides a detailed examination of Plato's arguments and the issues that they raise. He adjudicates on rival interpretations of the text, and looks at the relations between this and other works of Plato. The book does not presuppose any knowledge of Greek.