Of God and His Creatures

This perhaps is the best account that we have to render of evil. Evil lies at the root of things creatable, limited and imperfect: it is imbedded in the eternal possibilities of their nature: let but things exist in time, and certain evils, physical evils at any rate, are bound to arise. And given a realm of rational creatures, subject to physical evils, moral evils are not far off the frontier of such a kingdom.

Of God and His Creatures: 3.71