Sin is to a nature what blindness is to an eye. The blindness of an evil or defect which is a witness to the fact that the eye was created to see the light and, hence, the very lack of sight is the proof that the eye was meant... to be the one particularly capable of seeing the light. Were it not for this capacity, there would be no reason to think of blindness as a misforture.

Writings of Saint Augustine: The city of God (ed. 1954)