Moving on from Varro’s division between “mythical theology” and “civil theology,” Augustine now takes up the third major category, “natural theology,” for which he takes as his conversation partners the great philosophers of Greco-Roman civilization. He commends Socrates for promoting the conclusion that there must be one God who is the cause of all existence. He then offers a summary of the development of religious philosophy among Socrates’s diverse followers, all of whom carried forward different visions of Socrates’s idea of “the Highest Good.”

Augustine holds the Platonists to be the best school of philosophy following from Socrates, and in Plato’s classic threefold division of philosophy he sees a pattern for true worship. That threefold division is as follows: the study of things as they truly are (metaphysics), of truth and how we know it to be truth (epistemology), and of the right way to live (ethics). Augustine applies these categories to the Christian view of God and the spiritual life: “we should seek him in whom for us all things are held together, we should find him in whom for us all things are certain, we should love him, in whom is found all goodness” (304). He regards the Platonist view of God as “representing the closest approximation to our Christian position” (311).