Whether the gravity of a sin depends on its cause?

Objections

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.
Objection 2 : Further, concupiscence is a general cause of sin; wherefore a gloss on Rm. 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.
Objection 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.