Moral evil is evil that is wilfully inflicted upon the world by free moral agents. The problem of moral evil is the problem of reconciling the existence such evil with the existence of an omniscient, omnipotent and benevolent God. Surely if such a God existed, it is argued, he would prevent such evil from occurring.

This specific form of the generic argument from evil can be summarised as follows:

The Argument from Moral Evil

(1) If God exists then he is omniscient, omnipotent and benevolent.
(2) If God were omniscient, omnipotent and benevolent then the world would not contain moral evil.
(3) The world contains moral evil.
Therefore:
(4) It is not the case that God exists.

By far the most common response to the argument from moral evil is the free-will defence. The free-will defence is the argument that as moral evil results from the choices of free moral agents its existence is consistent with the existence of God. The argument works in two ways. First, it holds that as moral evil is caused by the choices of free moral agents, God is not responsible for moral evil. Second, it holds that as it is more important that free moral agents do exist than it is that moral evil does not exist, God did well in creating such agents even though he knew that they might choose to abuse their freedom.

A second counter to the argument from moral evil makes use of some of the principles of the moral argument for God’s existence. If God does not exist, this counter goes, then there would be no moral standards; everything would be permitted. If that were the case, though, then there could be no moral evil, for there would be no moral laws that could be violated. The fact that moral evil exists, then, far from disproving the existence of God, actually proves it. Just as the theist faces the problem of reconciling the existence of evil with the existence of God, the problem of evil, then, so the atheist faces the problem of reconciling the existence of morality with the non-existence of God, the problem of morality.