Chapter 049 - The Cause of Evil

Since evil is the deficiency of some good which a thing was created to possess, it has good for its cause; for nothing can be a cause except inasmuch as it has being, and being is good. This may be said of all causes, for we have seen that in material ones good is the subject of evil.

Evil, indeed, has not a formal cause, for it is the privation of form; nor has it a final cause, for it is the privation of the order which is due to the end; neither has it a cause by mode of agent, except accidentally, for the agent intends to introduce his own form, not to injure the opposite form. Thus evil is the deficiency of good, and has no cause except good.

Evil is twofold. One kind of evil belongs to action, through defect of the agent - this cannot be charged to God, in Whom there is no defect. The other is due to God, whether in things natural or voluntary; for the order of the universe requires that there should be some who may, and, consequently, among these some who do fail, and so promote the good of the universe, as it were, by accident. This is the cause of the corruption of certain things. And since the order of justice requires that sin should be punished, God is the Author of the evil of punishment, which is included in the idea of guilt.

But there is no supreme evil which is the cause of all other evils, as the Supreme Good is the Cause of all that is good: first, because the principle of all good is good by essence, while nothing can, by its essence, be evil; secondly, there is no supreme, that is to say integral, evil which consumes all good, for if all good were taken away, even that evil would be taken away of which good is the subject; thirdly, evil cannot be a principle, for it cannot be a cause except by accident.

The error of those who admitted two principles arose from their considering only particular causes, and not the Universal one, to which all things may be reduced as to a common principle of being, since they all agree in the participation of being.