Lactantius

“ 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. ”

“ 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 [1] to the demon, so that there should be one who might corrupt and destroy all things? ”

“ 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. ”