Summa Th. I-II EN Qu.73 a.4
Objection: 1. It would seem that the gravity of sins does not vary according to the excellence of the virtues to which they are opposed, so that, to wit, the graver the sin is opposed to the greater virtue. For, according to Pr 15,5, "In abundant justice there is the greatest strength." Now, as Our Lord says (Mt 5,20, seqq.) abundant justice restrains anger, which is a less grievous sin than murder, which less abundant justice restrains. Therefore the least grievous sin is opposed to the greatest virtue.
2. Further, it is stated in Ethic. ii, 3 that "virtue is about the difficult and the good": whence it seems to follow that the greater virtue is about what is more difficult. But it is a less grievous sin to fail in what is more difficult, than in what is less difficult. Therefore the less grievous sin is opposed to the greater virtue.
3. Further, charity is a greater virtue than faith or hope (1Co 13,13). Now hatred which is opposed to charity is a less grievous sin than unbelief or despair which are opposed to faith and hope. Therefore the less grievous sin is opposed to the greater virtue.
On the contrary The Philosopher says (Ethic. 8:10) that the "worst is opposed to the best." Now in morals the best is the greatest virtue; and the worst is the most grievous sin. Therefore the most grievous sin is opposed to the greatest virtue.
I answer that A sin is opposed to a virtue in two ways: first, principally and directly; that sin, to with, 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 (Question , Article ; Question , Article ). 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 to Objection: 1. This argument considers the opposition which consists in restraining from sin; for thus abundant justice checks even minor sins.
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.
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.
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 (Pr 6,30 Pr 6,32): "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.
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.
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.
I answer that Spiritual sins are of greater guilt than carnal sins: yet this does not mean that each spiritual sin is of greater guilt than each carnal sin; but that, considering the sole difference between spiritual and carnal, spiritual sins are more grievous than carnal sins, other things being equal. Three reasons may be assigned for this. The first is on the part of the subject: because spiritual sins belong to the spirit, to which it is proper to turn to God, and to turn away from Him; whereas carnal sins are consummated in the carnal pleasure of the appetite, to which it chiefly belongs to turn to goods of the body; so that carnal sin, as such, denotes more a "turning to" something, and for that reason, implies a closer cleaving; whereas spiritual sin denotes more a "turning from" something, whence the notion of guilt arises; and for this reason it involves greater guilt. A second reason may be taken on the part of the person against whom sin is committed: because carnal sin, as such, is against the sinner's own body, which he ought to love less, in the order of charity, than God and his neighbor, against whom he commits spiritual sins, and consequently spiritual sins, as such, are of greater guilt. A third reason may be taken from the motive, since the stronger the impulse to sin, the less grievous the sin, as we shall state further on (Article ). Now carnal sins have a stronger impulse, viz. our innate concupiscence of the flesh. Therefore spiritual sins, as such, are of greater guilt.
Reply to Objection: 1. Adultery belongs not only to the sin of lust, but also to the sin of injustice, and in this respect may be brought under the head of covetousness, as a gloss observes on Ep 5,5. "No fornicator, or unclean, or covetous person," etc.; so that adultery is so much more grievous than theft, as a man loves his wife more than his chattels.
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).
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 minds": hence, by these sins man is, so to speak, brutalized; for which same reason Gregory says (Moral. xxxi, 17) that they are more shameful.
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.
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.
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 Mt 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.The other causes of sin are extrinsic and remote, as it were, being those whereby the will is inclined to sin. Among these causes we must make a distinction; for some of them induce the will to sin in accord with the very nature of the will: such is the end, which is the proper object of the will; and by a such like cause sin is made more grievous, because a man sins more grievously if his will is induced to sin by the intention of a more evil end. Other causes incline the will to sin, against the nature and order of the will, whose natural inclination is to be moved freely of itself in accord with the judgment of reason. Wherefore those causes which weaken the judgment of reason (e.g. ignorance), or which weaken the free movement of the will, (e.g. weakness, violence, fear, or the like), diminish the gravity of sin, even as they diminish its voluntariness; and so much so, that if the act be altogether involuntary, it is no longer sinful.
Reply to Objection: 1. This argument considers the extrinsic moving cause, which diminishes voluntariness. The increase of such a cause diminishes the sin, as stated.
2. If concupiscence be understood to include the movement of the will, then, where there is greater concupiscence, there is a greater sin. But if by concupiscence we understand a passion, which is a movement of the concupiscible power, then a greater concupiscence, forestalling the judgment of reason and the movement of the will, diminishes the sin, because the man who sins, being stimulated by a greater concupiscence, falls through a more grievous temptation, wherefore he is less to be blamed. On the other hand, if concupiscence be taken in this sense follows the judgment of reason, and the movement of the will, then the greater concupiscence, the graver the sin: because sometimes the movement of concupiscence is redoubled by the will tending unrestrainedly to its object.
3. This argument considers the cause which renders the act involuntary, and such a cause diminishes the gravity of sin, as stated.
Objection: 1. It would seem that a circumstance does not aggravate a sin. Because sin takes its gravity from its species. Now a circumstance does not specify a sin, for it is an accident thereof. Therefore the gravity of a sin is not taken from a circumstance.
2. Further, a circumstance is either evil or not: if it is evil, it causes, of itself, a species of evil; and if it is not evil, it cannot make a thing worse. Therefore a circumstance nowise aggravates a sin.
3. Further, the malice of a sin is derived from its turning away (from God). But circumstances affect sin on the part of the object to which it turns. Therefore they do not add to the sin's malice.
On the contrary Ignorance of a circumstance diminishes sin: for he who sins through ignorance of a circumstance, deserves to be forgiven (Ethic. iii, 1). Now this would not be the case unless a circumstance aggravated a sin. Therefore a circumstance makes a sin more grievous.
I answer that As the Philosopher says in speaking of habits of virtue (Ethic. ii, 1,2), "it is natural for a thing to be increased by that which causes it." Now it is evident that a sin is caused by a defect in some circumstance: because the fact that a man departs from the order of reason is due to his not observing the due circumstances in his action. Wherefore it is evident that it is natural for a sin to be aggravated by reason of its circumstances. This happens in three ways. First, in so far as a circumstance draws a sin from one kind to another: thus fornication is the intercourse of a man with one who is not his wife: but if to this be added the circumstance that the latter is the wife of another, the sin is drawn to another kind of sin, viz. injustice, in so far as he usurps another's property; and in this respect adultery is a more grievous sin than fornication. Secondly, a circumstance aggravates a sin, not by drawing it into another genus, but only by multiplying the ratio of sin: thus if a wasteful man gives both when he ought not, and to whom he ought not to give, he commits the same kind of sin in more ways than if he were to merely to give to whom he ought not, and for that very reason his sin is more grievous; even as that sickness is the graver which affects more parts of the body. Hence Cicero says (Paradox. iii) that "in taking his father's life a man commits many sins; for he outrages one who begot him, who fed him, who educated him, to whom he owes his lands, his house, his position in the republic." Thirdly, a circumstance aggravates a sin by adding to the deformity which the sin derives from another circumstance: thus, taking another's property constitutes the sin of theft; but if to this be added the circumstance that much is taken of another's property, the sin will be more grievous; although in itself, to take more or less has not the character of a good or of an evil act.
Reply to Objection: 1. Some circumstances do specify a moral act, as stated above (Question , Article ). Nevertheless a circumstance which does not give the species, may aggravate a sin; because, even as the goodness of a thing is weighed, not only in reference to its species, but also in reference to an accident, so the malice of an act is measured, not only according to the species of that act, but also according to a circumstance.
2. A circumstance may aggravate a sin either way. For if it is evil, it does not follow that it constitutes the sin's species; because it may multiply the ratio of evil within the same species, as stated above. And if it be not evil, it may aggravate a sin in relation to the malice of another circumstance.
3. Reason should direct the action not only as regards the object, but also as regards every circumstance. Therefore one may turn aside from the rule of reason through corruption of any single circumstance; for instance, by doing something when one ought not or where one ought not; and to depart thus from the rule of reason suffices to make the act evil. This turning aside from the rule of reason results from man's turning away from God, to Whom man ought to be united by right reason.
Objection: 1. It would seem that a sin is not aggravated by reason of its causing more harm. Because the harm done is an issue consequent to the sinful act. But the issue of an act does not add to its goodness or malice, as stated above (Question , Article ). Therefore a sin is not aggravated on account of its causing more harm.
2. Further, harm is inflicted by sins against our neighbor. Because no one wishes to harm himself: and no one can harm God, according to Jb 35,6 Jb 35,8: "If thy iniquities be multiplied, what shalt thou do against Him? . . . Thy wickedness may hurt a man that is like thee." If, therefore, sins were aggravated through causing more harm, it would follow that sins against our neighbor are more grievous than sins against God or oneself.
3. Further, greater harm is inflicted on a man by depriving him of the life of grace, than by taking away his natural life; because the life of grace is better than the life of nature, so far that man ought to despise his natural life lest he lose the life of grace. Now, speaking absolutely, a man who leads a woman to commit fornication deprives her of the life of grace by leading her into mortal sin. If therefore a sin were more grievous on account of its causing a greater harm, it would follow that fornication, absolutely speaking, is a more grievous sin than murder, which is evidently untrue. Therefore a sin is not more grievous on account of its causing a greater harm.
On the contrary Augustine says (De Lib. Arb. iii, 14): "Since vice is contrary to nature, a vice is the more grievous according as it diminishes the integrity of nature." Now the diminution of the integrity of nature is a harm. Therefore a sin is graver according as it does more harm.
I answer that Harm may bear a threefold relation to sin. Because sometimes the harm resulting from a sin is foreseen and intended, as when a man does something with a mind to harm another, e.g. a murderer or a thief. In this case the quantity of harm aggravates the sin directly, because then the harm is the direct object of the sin. Sometimes the harm is foreseen, but not intended; for instance, when a man takes a short cut through a field, the result being that he knowingly injures the growing crops, although his intention is not to do this harm, but to commit fornication. In this case again the quantity of the harm done aggravates the sin; indirectly, however, in so far, to wit, as it is owing to his will being strongly inclined to sin, that a man does not forbear from doing, to himself or to another, a harm which he would not wish simply. Sometimes, however, the harm is neither foreseen nor intended: and then if this harm is connected with the sin accidentally, it does not aggravate the sin directly; but, on account of his neglecting to consider the harm that might ensue, a man is deemed punishable for the evil results of his action if it be unlawful. If, on the other hand, the harm follow directly from the sinful act, although it be neither foreseen nor intended, it aggravates the sin directly, because whatever is directly consequent to a sin, belongs, in a manner, to the very species of that sin: for instance, if a man is a notorious fornicator, the result is that many are scandalized; and although such was not his intention, nor was it perhaps foreseen by him, yet it aggravates his sin directly.But this does not seem to apply to penal harm, which the sinner himself incurs. Such like harm, if accidentally connected with the sinful act, and if neither foreseen nor intended, does not aggravate a sin, nor does it correspond with the gravity of the sin: for instance, if a man in running to slay, slips and hurts his foot. If, on the other hand, this harm is directly consequent to the sinful act, although perhaps it be neither foreseen nor intended, then greater harm does not make greater sin, but, on the contrary, a graver sin calls for the infliction of a greater harm. Thus, an unbeliever who has heard nothing about the pains of hell, would suffer greater pain in hell for a sin of murder than for a sin of theft: but his sin is not aggravated on account of his neither intending nor foreseeing this, as it would be in the case of a believer, who, seemingly, sins more grievously in the very fact that he despises a greater punishment, that he may satisfy his desire to sin; but the gravity of this harm is caused by the sole gravity of sin.
Reply to Objection: 1. As we have already stated (Question , Article ), in treating of the goodness and malice of external actions, the result of an action if foreseen and intended adds to the goodness and malice of an act.
2. Although the harm done aggravates a sin, it does not follow that this alone renders a sin more grievous: in fact, it is inordinateness which of itself aggravates a sin. Wherefore the harm itself that ensues aggravates a sin, in so far only as it renders the act more inordinate. Hence it does not follow, supposing harm to be inflicted chiefly by sins against our neighbor, that such sins are the most grievous, since a much greater inordinateness is to be found against which man commits against God, and in some which he commits against himself. Moreover we might say that although no man can do God any harm in His substance, yet he can endeavor to do so in things concerning Him, e.g. by destroying faith, by outraging holy things, which are most grievous sins. Again, a man sometimes knowingly and freely inflicts harm on himself, as in the case of suicide, though this be referred finally to some apparent good, for example, delivery from some anxiety.
3. This argument does not prove, for two reasons: first, because the murderer intends directly to do harm to his neighbors; whereas the fornicator who solicits the woman intends not to harm but pleasure; secondly, because murder is the direct and sufficient cause of bodily death; whereas no man can of himself be the sufficient cause of another's spiritual death, because no man dies spiritually except by sinning of his own will.
Objection: 1. It would seem that sin is not aggravated by reason of the condition of the person against whom it is committed. For if this were the case a sin would be aggravated chiefly by being committed against a just and holy man. But this does not aggravate a sin: because a virtuous man who bears a wrong with equanimity is less harmed by the wrong done him, than others, who, through being scandalized, are also hurt inwardly. Therefore the condition of the person against whom a sin is committed does not aggravate the sin.
2. Further, if the condition of the person aggravated the sin, this would be still more the case if the person be near of kin, because, as Cicero says (Paradox. iii): "The man who kills his slave sins once: he that takes his father's life sins many times." But the kinship of a person sinned against does not apparently aggravate a sin, because every man is most akin to himself; and yet it is less grievous to harm oneself than another, e.g. to kill one's own, than another's horse, as the Philosopher declares (Ethic. v, 11). Therefore kinship of the person sinned against does not aggravate the sin.
3. Further, the condition of the person who sins aggravates a sin chiefly on account of his position or knowledge, according to Sg 6,7: "The mighty shall be mightily tormented," and Lc 12,47: "The servant who knew the will of his lord . . . and did it not . . . shall be beaten with many stripes." Therefore, in like manner, on the part of the person sinned against, the sin is made more grievous by reason of his position and knowledge. But, apparently, it is not a more grievous sin to inflict an injury on a rich and powerful person than on a poor man, since "there is no respect of persons with God" (Col 3,25), according to Whose judgment the gravity of a sin is measured. Therefore the condition of the person sinned against does not aggravate the sin.
On the contrary Holy Writ censures especially those sins that are committed against the servants of God. Thus it is written (1R 19,14): "They have destroyed Thy altars, they have slain Thy prophets with the sword." Moreover much blame is attached to the sin committed by a man against those who are akin to him, according to Mi 7,6: "the son dishonoreth the father, and the daughter riseth up against her mother." Furthermore sins committed against persons of rank are expressly condemned: thus it is written (Jb 34,18): "Who saith to the king: 'Thou art an apostate'; who calleth rulers ungodly." Therefore the condition of the person sinned against aggravates the sin.
I answer that The person sinned against is, in a manner, the object of the sin. Now it has been stated above (Article ) that the primary gravity of a sin is derived from its object; so that a sin is deemed to be so much the more grave, as its object is a more principal end. But the principal ends of human acts are God, man himself, and his neighbor: for whatever we do, it is on account of one of these that we do it; although one of them is subordinate to the other. Therefore the greater or lesser gravity of a sin, in respect of the person sinned against, may be considered on the part of these three.First, on the part of God, to Whom man is the more closely united, as he is more virtuous or more sacred to God: so that an injury inflicted on such a person redounds on to God according to Zach. 2:8: "He that toucheth you, toucheth the apple of My eye." Wherefore a sin is the more grievous, according as it is committed against a person more closely united to God by reason of personal sanctity, or official station. On the part of man himself, it is evident that he sins all the more grievously, according as the person against whom he sins, is more united to him, either through natural affinity or kindness received or any other bond; because he seems to sin against himself rather than the other, and, for this very reason, sins all the more grievously, according to Si 14,5: "He that is evil to himself, to whom will he be good?" On the part of his neighbor, a man sins the more grievously, according as his sin affects more persons: so that a sin committed against a public personage, e.g. a sovereign prince who stands in the place of the whole people, is more grievous than a sin committed against a private person; hence it is expressly prohibited (Ex 22,28): "The prince of thy people thou shalt not curse." In like manner it would seem that an injury done to a person of prominence, is all the more grave, on account of the scandal and the disturbance it would cause among many people.
Reply to Objection: 1. He who inflicts an injury on a virtuous person, so far as he is concerned, disturbs him internally and externally; but that the latter is not disturbed internally is due to his goodness, which does not extenuate the sin of the injurer.
2. The injury which a man inflicts on himself in those things which are subject to the dominion of his will, for instance his possessions, is less sinful than if it were inflicted on another, because he does it of his own will; but in those things that are not subject to the dominion of his will, such as natural and spiritual goods, it is a graver sin to inflict an injury on oneself: for it is more grievous for a man to kill himself than another. Since, however, things belonging to our neighbor are not subject to the dominion of our will, the argument fails to prove, in respect of injuries done to such like things, that it is less grievous to sin in their regard, unless indeed our neighbor be willing, or give his approval.
3. There is no respect for persons if God punishes more severely those who sin against a person of higher rank; for this is done because such an injury redounds to the harm of many.
Objection: 1. It would seem that the excellence of the person sinning does not aggravate the sin. For man becomes great chiefly by cleaving to God, according to Si 25,13: "How great is he that findeth wisdom and knowledge! but there is none above him that feareth the Lord." Now the more a man cleaves to God, the less is a sin imputed to him: for it is written (2Ch 30,18-19): "The Lord Who is good will show mercy to all them, who with their whole heart seek the Lord the God of their fathers; and will not impute it to them that they are not sanctified." Therefore a sin is not aggravated by the excellence of the person sinning.
2. Further, "there is no respect of persons with God" (Rm 2,11). Therefore He does not punish one man more than another, for one and the same sin. Therefore a sin is not aggravated by the excellence of the person sinning.
3. Further, no one should reap disadvantage from good. But he would, if his action were the more blameworthy on account of his goodness. Therefore a sin is not aggravated by reason of the excellence of the person sinning.
On the contrary Isidore says (De Summo Bono ii, 18): "A sin is deemed so much the more grievous as the sinner is held to be a more excellent person."
I answer that Sin is twofold. There is a sin which takes us unawares on account of the weakness of human nature: and such like sins are less imputable to one who is more virtuous, because he is less negligent in checking those sins, which nevertheless human weakness does not allow us to escape altogether. But there are other sins which proceed from deliberation: and these sins are all the more imputed to man according as he is more excellent. Four reasons may be assigned for this. First, because a more excellent person, e.g. one who excels in knowledge and virtue, can more easily resist sin; hence Our Lord said (Lc 12,47) that the "servant who knew the will of his lord . . . and did it not . . . shall be beaten with many stripes." Secondly, on account of ingratitude, because every good in which a man excels, is a gift of God, to Whom man is ungrateful when he sins: and in this respect any excellence, even in temporal goods, aggravates a sin, according to Sg 6,7: "The mighty shall be mightily tormented." Thirdly, on account of the sinful act being specially inconsistent with the excellence of the person sinning: for instance, if a prince were to violate justice, whereas he is set up as the guardian of justice, or if a priest were to be a fornicator, whereas he has taken the vow of chastity. Fourthly, on account of the example or scandal; because, as Gregory says (Pastor. i, 2): "Sin becomes much more scandalous, when the sinner is honored for his position": and the sins of the great are much more notorious and men are wont to bear them with more indignation.
Reply to Objection: 1. The passage quoted alludes to those things which are done negligently when we are taken unawares through human weakness.
2. God does not respect persons in punishing the great more severely, because their excellence conduces to the gravity of their sin, as stated.
3. The man who excels in anything reaps disadvantage, not from the good which he has, but from his abuse thereof.
We must now consider the subject of vice or sin: under which head there are ten points of inquiry:
(1) Whether the will can be the subject of sin?
(2) Whether the will alone is the subject of sin?
(3) Whether the sensuality can be the subject of sin?
(4) Whether it can be the subject of mortal sin?
(5) Whether the reason can be the subject of sin?
(6) Whether morose delectation or non-morose delectation be subjected in the higher reason?
(7) Whether the sin of consent in the act of sin is subjected in the higher reason?
(8) Whether the lower reason can be the subject of mortal sin?
(9) Whether the higher reason can be the subject of venial sin?
(10) Whether there can be in the higher reason a venial sin directed to its proper object?
Objection: 1. It would seem that the will cannot be a subject of sin. For Dionysius says (Div. Nom. iv) that "evil is outside the will and the intention." But sin has the character of evil. Therefore sin cannot be in the will.
2. Further, the will is directed either to the good or to what seems good. Now from the fact that will wishes the good, it does not sin: and that it wishes what seems good but is not truly good, points to a defect in the apprehensive power rather than in the will. Therefore sin is nowise in the will.
3. Further, the same thing cannot be both subject and efficient cause of sin: because "the efficient and the material cause do not coincide" (Phys. 2, text. 70). Now the will is the efficient cause of sin: because the first cause of sinning is the will, as Augustine states (De Duabus Anim. x, 10,11). Therefore it is not the subject of sin.
On the contrary Augustine says (Retract. i, 9) that "it is by the will that we sin, and live righteously."
I answer that Sin is an act, as stated above (Question , Articles ,6). Now some acts pass into external matter, e.g. "to cut" and "to burn": and such acts have for their matter and subject, the thing into which the action passes: thus the Philosopher states (Phys. iii, text. 18) that "movement is the act of the thing moved, caused by a mover." On the other hand, there are acts which do not pass into external matter, but remain in the agent, e.g. "to desire" and "to know": and such are all moral acts, whether virtuous or sinful. Consequently the proper subject of sin must needs be the power which is the principle of the act. Now since it is proper to moral acts that they are voluntary, as stated above (Question , Article ; Question , Article ), it follows that the will, which is the principle of voluntary acts, both of good acts, and of evil acts or sins, is the principle of sins. Therefore it follows that sin is in the will as its subject.
Reply to Objection: 1. Evil is said to be outside the will, because the will does not tend to it under the aspect of evil. But since some evil is an apparent good, the will sometimes desires an evil, and in this sense is in the will.
2. If the defect in the apprehensive power were nowise subject to the will, there would be no sin, either in the will, or in the apprehensive power, as in the case of those whose ignorance is invincible. It remains therefore that when there is in the apprehensive power a defect that is subject to the will, this defect also is deemed a sin.
3. This argument applies to those efficient causes whose actions pass into external matter, and which do not move themselves, but move other things; the contrary of which is to be observed in the will; hence the argument does not prove.
Summa Th. I-II EN Qu.73 a.4