This lecture will be devoted to exploring the chief subjects of books V–VII of the Republic, including the call for philosopher-kings; the doctrine of the ideas; and the famous Cave metaphor. To begin to understand these notoriously difficult sections, it is helpful to see that they are all a part of what Socrates means by the health of the individual soul, the definition of “justice” in the individual. In fact, with his call for philosopher-kings, Socrates quietly replaces the just human being with the philosopher as the manifestation of the healthy human being, a proposition that both the doctrine of the ideas and the Cave image are meant to explain. Socrates’s ultimate aim in the Republic is a defense of philosophy, and it is here that we begin to see most clearly his defense strategy.