De libero arbitrio’s “faith seeking understanding” and rambling scriptural exegesis may seem to depart from the Platonist methods of C. Acad. The difference, I suggest, is scale. Like Sol. + De imm. an., De lib. arbit. 1 and 2 each presents a complete round of ARP. Book 3’s exploration of Genesis, while longer, functions analogously to the scriptural cues of earlier dialogues’ plausible conclusions. The key is another virtue: piety. Augustine defines this as (a) thinking of God in the highest terms, (b) thanking God for even minor goods and (c) taking responsibility for one’s own shortcomings. He presents this as prerequisite for fruitful philosophical inquiry. I suggest that the work’s two rounds of ARP aim to instill piety as preparation for book 3’s search for a scriptural answer to evil. Book 1’s discussion of sin instills (c), book 2’s proof for God’s existence instills (a) and its grades of goods instill (b). In book 3, Augustine addresses evil from theoretical and pastoral angles at once, identifying pride as the root of sin and nurturing piety as a remedy to it. My reading shows Augustine’s final dialogue to be tightly unified around a project firmly rooted in his first.