Augustine sets up an argument in his Confession that attempts to define evil. God is the author of everything. Augustine says, "nothing that exists could exist without You [God]" (Book I, Chapter II). Nothing in this world exists apart from God.
For Augustine, God is good because everything He made is good. Everything about God is good. No aspect of Him is lacking, false, or not good. However, the question of evil and from where it came still remains.
Augustine then asks himself where it was that evil came. Evil could not have come from God; it must have come from another source other than God. Because we clearly see evil in this world, did God allow it to enter? This would seem that God is not omnipotent.
Originally Augustine believed that evil had substance. However, his views changed later where he says, "If they were deprived of all goodness, they would be altogether nothing; therefore, as long as they are, they are good. Thus whatsoever things are, are good; and that evil whose origin I sought is not a substance" (Book VII, Chapter XII). Under this definition, Augustine is saying that evil has no substance. Instead, evil is the result of a removal of good until there is nothing left at which time the object or person would cease to exist in the physical realm.
Augustine approaches this issue from an entirely different perspective. He asks: Do we have any good evidence that God exists? If He does, is He good? Since all that God created is good and evil is not good, then evil is not something that God created. This was Augustine's solution, but the question still remains: What is evil?