Nicene and Post-Nicene Fathers, Vol. IV:
Writings in Connection with the Manichæan Controversy.: Chapter 17

Chapter 17.—Nature, in as Far as It is Nature, No Evil.

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.