In Plato's Theaetetus, Socrates engages a young geometry student in a conversation about the nature of knowledge. Beginning with the idea of knowledge as sensory perception, and then looking at knowledge as a form of belief, Socrates and Theaetetus draw out the problems inherent in these theories. The discussion takes place in the shadow of Socrates' trial and execution, and Socrates is called away before any conclusion is reached. Scholars have argued whether the lack of a definite answer to the central question, 'what is knowledge?', constitutes a rejection of Plato's own earlier theories. Witty and engaging despite its profound subject matter, Theaetetus is a fascinating look at the subject which has concerned philosophers since ancient times.