I have spent the last several weeks reading almost nothing but Augustine, and today his basic approach finally clicked for me: He just wanted to understand what he already believed. He looked at the dogmas of the faith, the liturgical rites, and the tradition he'd received from his predecessors and - rather than simply believing with no investigation - wanted to construct an intellectual understanding that made his beliefs make sense. For example he looked at the rite of infant baptism, which contains pronouncements about the remission of sins along with an exorcism and exsufflation for the infant just like it does for adults (since these are the exact same service), and tried to make sense of what "sin" is being remitted along with how the infant came under the influence of the devil in the first place. He took the entirety of the faith as true and truly God-inspired, believing it with his whole heart, and wanted to understand it as well with his whole mind - to whatever small degree that's actually possible for our limited rationality. I think this is one of the things that made him such a rarity not just in the Christian world, but in the history of mankind as a whole.