(from the Baker’s Encyclopedia of Christian Apologetics, Baker, 1999)

The theist responds that evil is not a thing or substance. Rather it is a lack or privation of a good thing that God made. Evil is a deprivation of some particular good. The essence of this position is summarized:

Evil is not a substance but a corruption of the good substances God made. Evil is like rust to a car or rot to a tree. It is a lack in good things, but it is not a thing in itself. Evil is like a wound in an arm or moth-holes in a garment. It exists only in another but not in itself.

It is important to note that a privation is not the same as mere absence. Sight is absent in a stone as well as in a blind person. But the absence of sight in the stone is not a privation. Absence of something that ought to be there. Since the stone by nature ought not to see, it is not deprived of sight, as is the blind man. Evil, then is a privation of some good that ought to be there. It is not a mere negation.

To say that evil is not a thing, but a lack in things, is not to claim that it is not real. Evil is a real lack in good things, as the blind person knows only so well. Evil is not a real substance, but it is a real privation in good substances. It is not an actual entity but a real corruption in an actual entity.

Evil as privation comes in different kinds. There are physical privations, such as mutilations and there are moral privations, such as a sexual perversity. Privation can be in substance (what something is) or in relationships (how it relates to others). There are not only bad things but there are bad relations between things. A relationship of love is a good one; hate is an evil one. Likewise, when a creature worships its Creator, it relates well; blaspheming the Creator is an evil relationship.

From this perspective, it follows that there is no such thing as something that is totally evil. If it were totally deprived of all good, it would be nothing. A totally rusty car is no car at all. And a totally moth-eaten garment is only a hanger in a closet. Evil, like a wound, can only exist in something else. A totally wounded arm means the person is maimed.

In view of this, something cannot be totally private, at least not in a metaphysical sense. A totally corrupted being would not exist at all. And a totally incapacitated will could not make any moral actions. One must take care not to carry human depravity so far that one destroys the ability to sin. There cannot be a supreme evil, for although evil lessens good, it can never totally destroy it. Nothing can be complete, unmitigated evil. For if all good were entirely destroyed—and this would be required for evil to be complete—evil itself would vanish since its subject, namely good, would no longer be there.

The fact that evil cannot be total in a metaphysical sense by no means implies that it cannot be total in a moral sense. A being can be totally (or, radically) depraved morally in the sense that evil has invaded every part of being. But the moral total depravity can only be extensive, not intensive. It can extend to every part of a person’s being, but it cannot destroy personal being. If it destroyed one’s person, there would no longer be a person to do evil. Total evil in this sense would destroy a person’s ability to do evil.

Classical theists described things in terms of their four causes: (1) efficient; (2) final; (3) formal, and (4) material. A human being has God as the efficient cause, God’s glory and their good as final cause, a soul as formal cause and a body as the material cause. However, since evil is not a substance, it has no formal cause, and its material cause is a good substance.

The efficient cause of moral evil is free choice, not directly but indirectly. There is no purpose (final cause) of evil. It is lack of proper order to the good end. Evil has no formal cause of its own. Rather, it is the destruction of form in another. Its material cause is a good but not its own. It exists only in a good thing as the corruption of it.

The Persistence of Evil. There is another aspect of the problem of evil. Why does God allow it? Even if he did not produce it, he does permit it. Yet he is all-powerful and could destroy it. So why doesn’t he do so?

The classical way to state the problem of the persistence of evil is this:

Put this way, the argument leaves open the possibility of a finite god, but theists reject such a concept. For every finite or limited being has a cause. So a finite god is only a creature that needs an infinite Creator. And since God is powerful, then he must be infinitely powerful. Likewise, since he is good, he must be infinitely good. So, a finite god is not an option for a theist. God has both the desire and ability needed to do anything possible.

Is it possible to destroy evil? The theist responds as follows:

It is impossible for God to do what is contradictory. He cannot make an affirmation to be true and false at the same time. He can do nothing which involves such an impossibility, such as, making a square circle or a stone so heavy he cannot lift it.

Even an omnipotent being cannot do anything. It can only do what is possible. But it is not possible to force people to freely choose the good. Forced freedom is a contradiction. Therefore, God cannot literally destroy all evil without annihilating free choice. The only way to destroy evil is to destroy the good of free choice. But when there is no moral free choice, then there is no possibility of moral good. Unless hate is possible, love is not possible. Where no creature can blaspheme, no creatures can worship either. Therefore, if God were to destroy all evil, he would have to destroy all good too.

However, theism holds that even though God could not destroy (annihilate) all evil without destroying all good, nevertheless, he can and will defeat (overcome) all evil without destroying free choice. The argument can be summarized as follows:

The infinite power and perfection of God guarantee the eventual defeat of evil. The fact that it is not yet accomplished in no way diminishes the certainty that it will be defeated. Even though evil cannot be destroyed without destroying free choice, nonetheless, it can be overcome.

An all-powerful God could, for example, separate good persons from evil ones according to what persons freely choose. Those who love God will be separated from those who do not. Those who desire the good but are hindered by evil will no longer have their good purposes frustrated. And those who do evil and are hampered by good influences will no longer be nagged by the proddings of good. Each, whether in heaven or hell, will have it according to their free choice. In this way God’s victory over evil would not violate free choice.