One cannot understand the literary form of a dialogue without understanding its philosophical project and vice versa. This dissertation seeks to establish how Augustine's Cassiciacum dialogues work as dialogues. Each of these works, Contra Academicos, De beata vita and De ordine, pursues two streams of inquiry: one dialectical, one self-reflexive. The first uses aporetic debates to identify problems with individuals' current beliefs. The second reflects on the act of debate as an instance of rational activity and through this draws attention to features of human rationality. The goal of all this is to change how the inquirer thinks about himself, to bring him to see some final theory as plausible ( probabile). We find all the elements of this method in earlier authors: aporia in Plato, self-reflection in Plotinus, plausible conclusions in Cicero. But in Augustine these are fused into a system, one which structures all seven of his dialogues. This study situates Augustine against this philosophical tradition and provides a fresh start for future work on his texts. Chapter 1 argues that standing scholarly debates have imposed an unhelpful set of concerns on the dialogues. Chapters 2 through 4 set out the basic literary and philosophical project of each dialogue. Chapter 5 argues that the three dialogues, taken as a set, are programmatic for a particular kind of philosophical undertaking, one which can be traced through Augustine's subsequent works.