The problem of evil (or argument from evil) is the problem of reconciling the existence of the evil in the world with the existence of an omniscient (all-knowing), omnipotent (all-powerful) and perfectly good God. The argument from evil is the atheistic argument that the existence of such evil cannot be reconciled with, and so disproves, the existence of such a God.

Christianity claims both that God created the world and that he sustains it. Christianity claims that God knows all things and is capable of all feats. Christianity claims that God is perfectly good, and wants only the best for his Creation. If each of these claims is true, though, then it is difficult to see why God allows the evil in the world to persist. The evil in the world thus appears to be at least strong and perhaps even conclusive evidence that at least one of these central claims of Christianity is false.

This discussion will distinguish between four different forms of the argument from evil: the argument from imperfection, the argument from natural evil, the argument from moral evil, and the argument from unbelief. Though each of these arguments presents a different problem for the theist to explain, a different reason for believing that atheism is true, each shares a common form. The four arguments are, of course, mutually consistent, and so can be and often are proposed together.

Each of the four arguments from evil begins with the claim that if God existed then the world would reach a certain standard. The standard anticipated differs between the different forms of the argument, each argument claiming that the evil named in its title—imperfection, natural evil, moral evil and unbelief respectively—would not exist in a world created and sustained by God.

In each of the arguments this claim is supported by an appeal to God’s nature. If God exists, it is said, then he is omniscient, omnipotent and benevolent. As such, it is suggested, God would know how to bring it about that the world met the anticipated standard, would be able to bring it about that that the universe met the anticipated standard, and would want to bring it about that the universe met the anticipated standard. If God knew how to, were able to, and wanted to do a thing, though, then surely he would do that thing. If God existed, then, it seems that he would bring it about that the world met the standard anticipated by the proponent of the argument from evil.

The next step in each of the arguments from evil is the claim that the world does indeed contain the evil named, that the world does not reach the standard that it would reach if God existed. The four arguments thus claim respectively that the universe is imperfect, that it contains natural evil, that it contains moral evil, and that it contains unbelief. Each argument concludes from its respective claim that God does not exist. The argument from evil can, then, be represented as having the following structure:

The Argument from Evil

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

Some attempts to solve the problem of evil are general, applying equally to all of its forms. It is sometimes argued, for instance, that God is not morally good, and so that the first premise of the argument from evil is false. The third premise has also been questioned; there are some that deny that evil exists. If either of these solutions is successful, then all forms of the argument from evil fail.

Most attempts to solve the problem of evil, however, question the second premise of a specific form of the argument. A discussion of each of the four forms of the argument—the argument from imperfection, the argument from natural evil, the argument from moral evil, and the argument from unbelief—can be found by following the appropriate link.