Although Augustine has been using Neoplatonic terms and ideas throughout the Confessions thus far, it isn't until Book VII that he reaches the point in his autobiography when he first reads Neoplatonic philosophy. This is a watershed moment for the young Augustine, who finds in Neoplatonism a way of reconciling his long pursuit of philosophy with his new and serious faith in the Catholic church. The union of this philosophy and this theology will guide his work (including the Confessions) for the rest of his life.
[VII.1-7] Augustine begins with another appraisal of his philosophy at the time, paying particular attention to his conceptions of God as a being and of the nature of evil (the two concepts that Neoplatonism would alter most for him). The problem of picturing God remained central. Having rejected Manichee dualism, Augustine was finally trying to imagine God as "incorruptible and inviolable and unchangeable" rather than as some kind of limited, partly impotent substance.
He still, however, has no conception of spiritual substance (a substance that is not matter and does not exist in space). He pictured God as "a secret breath of life" or like sunlight, when he shouldn't have been "picturing" him at all. "My eyes are accustomed to such images," he writes, and "my heart accepted the same structure. Augustine couldn't get around the idea that anything not occupying space could still have existence. (He notes that even the power of thought itself, if he had considered it, would have served as an example).
Similarly, although Augustine now thought of Manichee dualism as "an abomination," he still had no solution to the problem of evil. He even reached the point of suspecting (after listening to other Catholics) that human free will causes evil, but was left with the question of why humans can choose evil at all. How could it even be an option to choose something other than God, if God is omnipotent?
This problem, too, Augustine now attributes to improper visualization. He thought of God like an immense ocean, with the world as "a large but finite sponge" within it. Thus, he asked, "how [did] evil creep in?" And if matter itself was evil (as the Manicheans taught), why did God create it?
[VII.8-22] After a brief discussion of astrology (which, in a conversation with a prominent astrologer called Firminus, he finds as improbable as ever), Augustine turns to his Neoplatonic experience. Picking up a Neoplatonic text, he read what seemed to be almost another version of Genesis. The book (he doesn't name it) struck Augustine as thrillingly similar to Genesis, and authoritatively contrary to Manichee dualism.