The free-will defence is a defence of theism against the argument from moral evil. The argument from moral evil is the argument that the existence of moral evil is inconsistent with, and so disproves, the existence of God. (Moral evil is simply evil resulting from the free actions of moral agents.) The argument from moral evil has the following form:

The Argument from Moral Evil

(1) If God exists then he is omnipotent, omniscient, and benevolent.
(2) If God were omnipotent, omniscient, 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.

Like all forms of the argument from evil, the key premise of the argument from moral evil is the second. Is it the case that if God were omnipotent, omniscient and benevolent then the world would not contain moral evil? If so, then the argument from moral evil appears to be sound; there is little else in the argument that admits of dispute.

In order to refute the argument from moral evil, then, the theist must show that it is not necessarily the case that if God were omnipotent, omniscient, and benevolent then the world would not contain moral evil. Under what circumstances, though, for what reason, might such a God allow such evil?

Theists almost invariably meet this question with the free-will defence. Moral evil is caused by the free choices of moral agents, they argue. Free agency, though, is a good thing; a world containing free agents is far better than either a world containing only automata or a world containing no conscious beings at all. An omniscient, omnipotent and benevolent God would therefore create a world containing free agents, and in doing so would run the risk of allowing moral evil to enter into the world.

The first way in which the free-will defence works, then, is by distancing God from the moral evil in the world. Moral evil is not brought about by God, the free-will defence argues, but by free agents. God is therefore not the author of moral evil, and so is not responsible for it.

This conclusion might be criticised, however, in the following way: Even if it is the free agents that perpetrate moral evils that are directly responsible for them, God does seem to bear at least some indirect responsibility for them. After all, God created the free agents, knowing full well the risk that he was running in doing so, and is therefore at least partly to blame for their abuses of their freedom. God it can be argued, is guilty of negligence in creating free agents, even if not of actually perpetrating any moral crimes himself.

The second way in which the free-will defence works is in justifying the existence of moral evil by justifying God’s creation of free agents. The existence of moral evil, the free-will defence argues, is a consequence of the existence of a greater good: free will. Without free will there could be no moral goodness; a world without free agents would be morally void. The good that is the existence of free moral agents, it is suggested, therefore outweighs the bad that is the existence of moral evil, and God therefore did well in creating free agents even though he knew that some of them would commit moral evils.

Some have criticised this line of defence by arguing that the good that is the existence of free moral agents does not outweigh the bad that is the existence of moral evil. Consider the scale on which moral evil has occurred even in recent history; this is a high price to pay for freedom; is it too high a price?

Others have thought that the free-will defence fails because God could have created free agents without risking bringing moral evil into the world. There is nothing logically inconsistent about a free agent that always chooses the good. There are, then, among all of the possible free agents that God might have created, some free agents that would always have chosen the good. Why, it is sometimes asked, did God not create those free agents, leaving the others uncreated?

A further criticism of the free-will defence imagines a human being using it to justify his failure to intervene to prevent a crime from being committed. If one of us were able to prevent a brutal murder, but instead allowed it to take place, then we could not justify our inaction using the free-will defence. If we were to say that although we could have prevented the murder, we thought it best to protect the free-will of the murderer by allowing him to carry out his plan, then we would be judged to have made a moral error. Why, if this argument would be unacceptable coming from a human being, should we think it any more acceptable coming from God?