This guide to Plato's Theaetetus is both an introduction to philosophy and an analysis of the dialogue according to the three acts of the mind. It suggests that Plato explores the problem of knowledge by means of a philosophical anthropology which presents us with one of the earliest accounts of the three acts of the mind (apprehension, judgment, and reason). By means of this philosophic anthropology, Plato delves into the character of wisdom, wonder, friendship, knowledge, ethics, and the divine. The Theaetetus and this Commentary explore these major psychological acts which allow us to understand the world. This Commentary places Plato's dialogue in conversation with subsequent philosophy and Christian wisdom.