"Theaetetus" is a philosophical dialogue written by the ancient Greek philosopher Plato, believed to have been written in the late 4th century BCE. The dialogue is named after its main character, a young mathematician named Theaetetus who is being questioned by the philosopher Socrates. The dialogue explores the nature of knowledge, with Socrates questioning Theaetetus about his understanding of different forms of knowledge, such as perception, belief, and true knowledge. Throughout this book, Plato uses the character of Socrates to express his own philosophical views about knowledge and the nature of reality. The dialogue also includes a discussion about the role of the philosopher and the pursuit of wisdom, with Socrates arguing that true knowledge can only be attained through philosophical inquiry and contemplation. "Theaetetus" is considered one of Plato's most important dialogues, and it has had a significant influence on Western philosophy.