A dialogue, written by Plato around 369 BCE, features Socrates and the young geometry student Theaetetus discussing the nature of knowledge. Theaetetus initially suggests that knowledge is perception, influenced by Protagoras's theory that "man is the measure of all things." Socrates examines the idea that everything is in constant change, which impacts perception. They explore whether knowledge can be defined as true judgment, but find issues with misperception. Finally, they consider knowledge as true judgment with an account, but this definition also proves inadequate. Campbell's edition includes a revised text and detailed notes.