In Augustine Confessions, Book Seven, Augustine talks about his views on the origin of evil. The first thing he talks about is how evil exists because of our free will (119). Augustine states how God would not have created evil because He is not able to be corrupted (120). God could not let evil into the world because evil is corrupted while God is incorruptible (120). Free will allows evil to come into because it gives humans a choice to either commit an evil act or not.
Augustine then goes on and states how human evil is the disorder of one’s passions ruling over one’s soul/reasoning. He states when trying to achieve a goal virtuously, one gets misguided due to his passions ruling and does it in an evil manner (121).