"Theaetetus" is a philosophical dialogue written by Plato that explores the nature of knowledge and the problem of knowledge acquisition. The book takes its name from the main character, a young mathematician named Theaetetus. The dialogue begins with Socrates engaging Theaetetus in a discussion about the nature of knowledge. They explore the question of what knowledge is, and how it can be acquired. They discuss various definitions of knowledge, such as the idea that knowledge is perception or true belief.