Like shadow is to light, so it evil to good…
“One helpful approach to solving the problem of evil has to do with defining evil. Christian thinker Augustine defined evil not as a thing in and of itself, but as a parasite on good. Something that is lacking is not a thing in itself. For instance, if you have a hole in your jacket, the hole is not something, but rather is something that is lacking.”
“In this sense, Augustine defined evil as a privation – a lack of something – rather than a thing or substance.”
“This solves some important criticisms. If evil is not an actual thing, then God cannot be the author of evil. God is the author of good, but we make moral choices that result in evil.”
Read more here: How Can God Allow So Much Evil and Suffering?
Related: God, Evil and Suffering.