Reply Obj. 2:  The devil is said to rejoice chiefly in the sin of lust, because it is of the greatest adhesion, and man can with difficulty be withdrawn from it.  “For the desire of pleasure is insatiable,” as the Philosopher states (Ethic. iii, 12).

Reply Obj. 3:  As the Philosopher himself says (Ethic. vii, 6), the reason why it is more shameful to be incontinent in lust than in anger, is that lust partakes less of reason; and in the same sense he says (Ethic. iii, 10) that “sins of intemperance are most worthy of reproach, because they are about those pleasures which are common to us and irrational animals”:  hence, by these sins man is, so to speak, brutalized; for which same reason Gregory says (Moral. xxxi, 17) that they are more shameful. ________________________

SIXTH ARTICLE [I-II, Q. 73, Art. 6]

Whether the Gravity of a Sin Depends on Its Cause?

Objection 1:  It would seem that the gravity of a sin does not depend on its cause.  Because the greater a sin’s cause, the more forcibly it moves to sin, and so the more difficult is it to resist.  But sin is lessened by the fact that it is difficult to resist; for it denotes weakness in the sinner, if he cannot easily resist sin; and a sin that is due to weakness is deemed less grievous.  Therefore sin does not derive its gravity from its cause.

Obj. 2:  Further, concupiscence is a general cause of sin; wherefore a gloss on Rom. 7:7, “For I had not known concupiscence,” says:  “The law is good, since by forbidding concupiscence, it forbids all evils.”  Now the greater the concupiscence by which man is overcome, the less grievous his sin.  Therefore the gravity of a sin is diminished by the greatness of its cause.

Obj. 3:  Further, as rectitude of the reason is the cause of a virtuous act, so defect in the reason seems to be the cause of sin.  Now the greater the defect in the reason, the less grievous the sin:  so much so that he who lacks the use of reason, is altogether excused from sin, and he who sins through ignorance, sins less grievously.  Therefore the gravity of a sin is not increased by the greatness of its cause.

On the contrary, If the cause be increased, the effect is increased.  Therefore the greater the cause of sin, the more grievous the sin.

I answer that, In the genus of sin, as in every other genus, two causes may be observed.  The first is the direct and proper cause of sin, and is the will to sin:  for it is compared to the sinful act, as a tree to its fruit, as a gloss observes on Matt. 7:18, “A good tree cannot bring forth evil fruit”:  and the greater this cause is, the more grievous will the sin be, since the greater the will to sin, the more grievously does man sin.