Where does evil come from?
Either God wants to abolish evil, and cannot; or he can, but does not want to. If he wants to, but cannot, he is impotent. If he can, but does not want to, he is wicked. If God can abolish evil, and God really wants to do it, why is there evil in the world? – Epicurus, as quoted in 2000 Years of Disbelief
Augustine stated that natural evil (evil present in the natural world such as natural disasters etc.) is caused by fallen angels, whereas moral evil (evil caused by the will of human beings) is as a result of man having become estranged from God and choosing to deviate from his chosen path. Augustine argued that God could not have created evil in the world, as it was created good, and that all notions of evil are simply a deviation or privation of goodness. Evil cannot be a separate and unique substance. For example, Blindness is not a separate entity, but is merely a lack or privation of sight. Thus the Augustinian theodicist would argue that the problem of evil and suffering is void because God did not create evil; it was man who chose to deviate from the path of perfect goodness.
Both Luther and Calvin explained evil as a consequence of the fall of man and the original sin. However, due to the belief in predestination and omnipotence, the fall is part of God's plan. Ultimately humans may not be able to understand and explain this plan.
"And we know that all things work together for good to them that love God, to them who are the called according to his purpose." Romans 8:28