Concerning the Nature of Good, Against the Manichæans 17
17 Nature, in as Far as It is Nature, No Evil PL 42, 556
No nature, therefore, as far as it is nature, is evil; but to each nature there is no evil except to be diminished in respect of good. But if by being diminished it should be consumed so that there is no good, no nature would be left; not only such as the Manichæans introduce, where so great good things are found that their exceeding blindness is wonderful, but such as any one can introduce.
Natura in quantum natura est, nulla mala. Non ergo mala est, in quantum natura est, ulla natura; sed cuique naturae non est malum nisi minui bono. Quod si minuendo absumeretur, sicut nullum bonum, ita nulla natura relinqueretur: non solum qualem inducunt Manichaei, ubi tanta bona inveniuntur, ut nimia eorum caecitas mira sit; sed qualem potest quilibet inducere.