In this dissertation I argue for an interpretation of Socrates' views about desire and motivation in Plato's Gorgias and Republic. These views are founded on two theses: the Reality Thesis, according to which all desire is for what is really good; and the Appearance Thesis, according to which whenever we act, we must believe that what we do is good, and that our desiderative objects are good. I argue that Socrates maintains these theses in both dialogues, but that in the Republic he develops them in several novel directions as he divides the soul, and as he characterizes ontologically lower objects as images, likenesses or imitations of ontologically higher objects. The Reality Thesis affirms that the ultimate object of our desires is a real thing out there in the world, regardless of whether we grasp its nature; it names the master value that we desire to realize in each action we undertake, and to obtain in each object we pursue; and it identifies the common aim of the psychic forces that motivate all of our actions. I argue that we can understand Socrates’ commitment to the Reality Thesis if we take him to be a “provisionalist” about desire: he believes that each desire on which we act is for its object, provided that object is good. This view enables us to explain the provocative conclusion of Socrates’ argument at Gorgias 467c-468e: if someone does what is not good, she does not do what she wants. This conclusion is true because of a feature of our psychological condition, namely that every desire on which we act is for its object, provided that object is good. The intentional content of the motivating desire explains why doing what is good is necessary for doing what we want, even when we are unaware of whether what we do is good. I also defend a “maximalist” interpretation of the Appearance Thesis, according to which whenever we act, we believe that what we do is fine and virtuous, that our action comports with our sense of what living well entails. I argue for this interpretation by examining the portrayals of several related figures in the Gorgias – primarily Callicles, orators and their audiences – all of whom construe their actions and desiderative objects as fine and virtuous. And I find evidence for a maximalist interpretation of the Appearance Thesis in several features of the Republic: agents habitually mistake the ontologically lower objects of their desires for the ontologically higher objects that they imitate; the lowest part of the soul sees its desiderative objects as fine and virtuous; characters like the democratic and the tyrannical man believe their actions and desiderative objects are fine and virtuous, and these beliefs belong to the lowest parts of their souls. As with Callicles, orators and their audiences in the Gorgias, these characters serve as useful test cases for the maximalist interpretation of the Appearance Thesis – if it applies to agents like these, it applies to all agents.