Traité des habitus

Obj. 1: It would seem that sin has no cause. For sin has the nature of evil, as stated above (Q. 71, A. 6). But evil has no cause, as Dionysius says (Div. Nom. iv). Therefore sin has no cause. Obj. 2: Further, a cause is that from which something follows of necessity. Now that which is of necessity, seems to be no sin, for every sin is voluntary. Therefore sin has no cause. Obj. 3: Further, if sin has a cause, this cause is either good or evil. It is not a good, because good produces nothing but good, for "a good tree cannot bring forth evil fruit" (Matt. 7:18). Likewise neither can evil be the cause of sin, because the evil of punishment is a sequel to sin, and the evil of guilt is the same as sin. Therefore sin has no cause. On the contrary, Whatever is done has a cause, for, according to Job 5:6, "nothing upon earth is done without a cause." But sin is something done; since it a "word, deed, or desire contrary to the law of God." Therefore sin has a cause. I answer that, A sin is an inordinate act. Accordingly, so far as it is an act, it can have a direct cause, even as any other act; but, so far as it is inordinate, it has a cause, in the same way as a negation or privation can have a cause. Now two causes may be assigned to a negation: in the first place, absence of the cause of affirmation; i.e. the negation of the cause itself, is the cause of the negation in itself; since the result of removing the cause is the removal of the effect: thus the absence of the sun is the cause of darkness.…