The Divine Institutes

But some one says: Why, then, does the true God permit these things to be done? Why does He not rather remove or destroy the wicked? Why, in truth, did He from the beginning give power to the demon, so that there should be one who might corrupt and destroy all things? I will briefly say why He willed that this should be so. I ask whether virtue is a good or an evil. It cannot be denied that it is a good. If virtue is a good, vice, on the contrary, is an evil. If vice is an evil on this account, because it opposes virtue, and virtue is on this account a good, because it overthrows vice, it follows that virtue cannot exist without vice; and if you take away vice, the merits of virtue will be taken away. For there can be no victory without an enemy. Thus it comes to pass, that good cannot exist without an evil.

Chrysippus, a man of active mind, saw this when discussing the subject of providence, and charges those with folly who think that good is caused by God, but say that evil is not thus caused. Aulus Gellius has interpreted his sentiment in his books of Attic Nights; thus saying: “They to whom it does not appear that the world was made for the sake of God and men, and that human affairs are governed by providence, think that they use a weighty argument when they thus speak: If there were a providence, there would be no evils. For they say that nothing is less in agreement with providence, than that in this world, on account of which it is said that God made men, the power of troubles and evils should be so great. In reply to these things, Chrysippus, when he was arguing, in his fourth book respecting providence, said: Nothing can be more foolish than those who think that good things could have existed, if there were not evils in the same place. For since good things are contrary to evil, they must of necessity be opposed to each other, and must stand resting, as it were, on mutual and opposite support. Thus there is no contrary without another contrary. For how could there be any perception of justice, unless there were injuries? or what else is justice, but the removal of injustice? In like manner, the nature of fortitude cannot be understood, except by placing beside it cowardice, or the nature of self-control except by intemperance. Likewise, in what manner would there be prudence, unless there were the contrary, imprudence? On the same principle, he says, why do the foolish men not require this also, that there should be truth and not falsehood? For there exist together good and evil things, prosperity and trouble, pleasure and pain. For the one being bound to the other at opposite poles, as Plato says, if you take away one, you take away both.” You see, therefore, that which I have often said, that good and evil are so connected with one another, that the one cannot exist without the other. Therefore God acted with the greatest foresight in placing the subject-matter of virtue in evils which He made for this purpose, that He might establish for us a contest, in which He would crown the victorious with the reward of immortality.