I answer that, A sin is opposed to a virtue in two ways: first, principally and directly; that sin, to wit, which is about the same object: because contraries are about the same thing. In this way, the more grievous sin must needs be opposed to the greater virtue: because, just as the degrees of gravity in a sin depend on the object, so also does the greatness of a virtue, since both sin and virtue take their species from the object, as shown above (Q. 60, A. 5; Q. 72, A. 1). Wherefore the greatest sin must needs be directly opposed to the greatest virtue, as being furthest removed from it in the same genus. Secondly, the opposition of virtue to sin may be considered in respect of a certain extension of the virtue in checking sin. For the greater a virtue is, the further it removes man from the contrary sin, so that it withdraws man not only from that sin, but also from whatever leads to it. And thus it is evident that the greater a virtue is, the more it withdraws man also from less grievous sins: even as the more perfect health is, the more does it ward off even minor ailments. And in this way the less grievous sin is opposed to the greater virtue, on the part of the latter's effect.
Reply Obj. 1: This argument considers the opposition which consists in restraining from sin; for thus abundant justice checks even minor sins.
Reply Obj. 2: The greater virtue that is about a more difficult good is opposed directly to the sin which is about a more difficult evil. For in each case there is a certain superiority, in that the will is shown to be more intent on good or evil, through not being overcome by the difficulty.
Reply Obj. 3: Charity is not any kind of love, but the love of God: hence not any kind of hatred is opposed to it directly, but the hatred of God, which is the most grievous of all sins. ________________________
FIFTH ARTICLE [I-II, Q. 73, Art. 5]
Whether Carnal Sins Are of Less Guilt Than Spiritual Sins?
Objection 1: It would seem that carnal sins are not of less guilt than spiritual sins. Because adultery is a more grievous sin than theft: for it is written (Prov. 6:30, 32): "The fault is not so great when a man has stolen . . . but he that is an adulterer, for the folly of his heart shall destroy his own soul." Now theft belongs to covetousness, which is a spiritual sin; while adultery pertains to lust, which is a carnal sin. Therefore carnal sins are of greater guilt than spiritual sins.
Obj. 2: Further, Augustine says in his commentary on Leviticus [*The quotation is from De Civ. Dei ii, 4 and iv, 31.] that "the devil rejoices chiefly in lust and idolatry." But he rejoices more in the greater sin. Therefore, since lust is a carnal sin, it seems that the carnal sins are of most guilt.
Obj. 3: Further, the Philosopher proves (Ethic. vii, 6) that "it is more shameful to be incontinent in lust than in anger." But anger is a spiritual sin, according to Gregory (Moral. xxxi, 17); while lust pertains to carnal sins. Therefore carnal sin is more grievous than spiritual sin.
On the contrary, Gregory says (Moral. xxxiii, 11) that carnal sins are of less guilt, but of more shame than spiritual sins.