De libero arbitrio voluntatis
De libero arbitrio voluntatis (On Free Choice of the Will), often shortened to De libero arbitrio, is a book by Augustine of Hippo which seeks to resolve the problem of evil in Christianity by asserting that free will is the cause of all suffering. The first of its three volumes was completed in 388; the second and third were written between 391 and 395.
Source: Wikipedia — De libero arbitrio voluntatis (CC BY-SA 4.0)