One of the main themes of the City of God is human flourishing, and the one thing that threatens human flourishing is evil, and sufferings caused by evil.
In this book, Augustine gives a classical / Augustinian definition of evil, and explains the origin and end of evil in a world created by God, who is Supremely Good.
In this book, Augustine gives a classical / Augustinian definition of evil, and explains the origin and end of evil in a world created by God, who is Supremely Good.