Evil Arises Not from a Substance, But from the Perversion of the Will
22 And I discerned and found it no marvel, that bread which is distasteful to an unhealthy palate is pleasant to a healthy one; and that the light, which is painful to sore eyes, is delightful to sound ones. And Your righteousness displeases the wicked; much more the viper and little worm, which You have created good, fitting in with inferior parts of Your creation; with which the wicked themselves also fit in, the more in proportion as they are unlike You, but with the superior creatures, in proportion as they become like to You. And I inquired what iniquity was, and ascertained it not to be a substance, but a perversion of the will, bent aside from You, O God, the Supreme Substance, towards these lower things, and casting out its bowels, and swelling outwardly.
Source: Confessions (New Advent)