Let them not then say, that he who does wrong and sins transgresses through the agency of demons; for then he would be guiltless. But by choosing the same things as demons, by sinning, being unstable, and light, and fickle in his desires, like a demon, he becomes a demoniac man. Now he who is bad, having become, through evil, sinful by nature, becomes depraved, having what he has chosen; and being sinful, sins also in his actions. And again, the good man does right. Wherefore we call not only the virtues, but also right actions, good. And of things that are good we know that some are desirable for themselves, as knowledge; for we hunt for nothing from it when we have it, but only [seek] that it be with us, and that we be in uninterrupted contemplation, and strive to reach it for its own sake. But other things are desirable for other considerations, such as faith, for escape from punishment, and the advantage arising from reward, which accrue from it. For, in the case of many, fear is the cause of their not sinning; and the promise is the means of pursuing obedience, by which comes salvation. Knowledge, then, desirable as it is for its own sake, is the most perfect good; and consequently the things which follow by means of it are good. And punishment is the cause of correction to him who is punished; and to those who are able to see before them he becomes an example, to prevent them falling into the like.