Summa Theologica, by St. Thomas Aquinas, [1947], at sacred-texts.com
We have now to consider the consequences of human actions by reason of their goodness and malice: and under this head there are four points of inquiry:
(1) Whether a human action is right or sinful by reason of its being good or evil?
(2) Whether it thereby deserves praise or blame?
(3) Whether accordingly, it is meritorious or demeritorious?
(4) Whether it is accordingly meritorious or demeritorious before God?
Objection 1: It seems that a human action is not right or sinful, in so far as it is good or evil. For "monsters are the sins of nature" (Phys. ii, 8). But monsters are not actions, but things engendered outside the order of nature. Now things that are produced according to art and reason imitate those that are produced according to nature (Phys. ii, 8). Therefore an action is not sinful by reason of its being inordinate and evil.
Objection 2: Further, sin, as stated in Phys. ii, 8 occurs in nature and art, when the end intended by nature or art is not attained. But the goodness or malice of a human action depends, before all, on the intention of the end, and on its achievement. Therefore it seems that the malice of an action does not make it sinful.
Objection 3: Further, if the malice of an action makes it sinful, it follows that wherever there is evil, there is sin. But this is false: since punishment is not a sin, although it is an evil. Therefore an action is not sinful by reason of its being evil.
On the contrary, As shown above (Q[19], A[4]), the goodness of a human action depends principally on the Eternal Law: and consequently its malice consists in its being in disaccord with the Eternal Law. But this is the very nature of sin; for Augustine says (Contra Faust. xxii, 27) that "sin is a word, deed, or desire, in opposition to the Eternal Law." Therefore a human action is sinful by reason of its being evil.
I answer that, Evil is more comprehensive than sin, as also is good than right. For every privation of good, in whatever subject, is an evil: whereas sin consists properly in an action done for a certain end, and lacking due order to that end. Now the due order to an end is measured by some rule. In things that act according to nature, this rule is the natural force that inclines them to that end. When therefore an action proceeds from a natural force, in accord with the natural inclination to an end, then the action is said to be right: since the mean does not exceed its limits, viz. the action does not swerve from the order of its active principle to the end. But when an action strays from this rectitude, it comes under the notion of sin.
Now in those things that are done by the will, the proximate rule is the human reason, while the supreme rule is the Eternal Law. When, therefore, a human action tends to the end, according to the order of reason and of the Eternal Law, then that action is right: but when it turns aside from that rectitude, then it is said to be a sin. Now it is evident from what has been said (Q[19], AA[3],4) that every voluntary action that turns aside from the order of reason and of the Eternal Law, is evil, and that every good action is in accord with reason and the Eternal Law. Hence it follows that a human action is right or sinful by reason of its being good or evil.
Reply to Objection 1: Monsters are called sins, inasmuch as they result from a sin in nature's action.
Reply to Objection 2: The end is twofold; the last end, and the proximate end. In the sin of nature, the action does indeed fail in respect of the last end, which is the perfection of the thing generated; but it does not fail in respect of any proximate end whatever; since when nature works it forms something. In like manner, the sin of the will always fails as regards the last end intended, because no voluntary evil action can be ordained to happiness, which is the last end: and yet it does not fail in respect of some proximate end: intended and achieved by the will. Wherefore also, since the very intention of this end is ordained to the last end, this same intention may be right or sinful.
Reply to Objection 3: Each thing is ordained to its end by its action: and therefore sin, which consists in straying from the order to the end, consists properly in an action. On the other hand, punishment regards the person of the sinner, as was stated in the FP, Q[48], A[5], ad 4; A[6], ad 3.
Objection 1: It would seem that a human action does not deserve praise or blame by reason of its being good or evil. For "sin happens even in things done by nature" (Phys. ii, 8). And yet natural things are not deserving of praise or blame (Ethic. iii, 5). Therefore a human action does not deserve blame, by reason of its being evil or sinful; and, consequently, neither does it deserve praise, by reason of its being good.
Objection 2: Further, just as sin occurs in moral actions, so does it happen in the productions of art: because as stated in Phys. ii, 8 "it is a sin in a grammarian to write badly, and in a doctor to give the wrong medicine." But the artist is not blamed for making something bad: because the artist's work is such, that he can produce a good or a bad thing, just as he lists. Therefore it seems that neither is there any reason for blaming a moral action, in the fact that it is evil.
Objection 3: Further, Dionysius says (Div. Nom. iv) that evil is "weak and incapable." But weakness or inability either takes away or diminishes guilt. Therefore a human action does not incur guilt from being evil.
On the contrary, The Philosopher says (De Virt. et Vit. i) that "virtuous deeds deserve praise, while deeds that are opposed to virtue deserve censure and blame." But good actions are virtuous; because "virtue makes that which has it, good, and makes its action good" (Ethic. ii, 6): wherefore actions opposed to virtue are evil. Therefore a human action deserves praise or blame, through being good or evil.
I answer that, Just as evil is more comprehensive than sin, so is sin more comprehensive than blame. For an action is said to deserve praise or blame, from its being imputed to the agent: since to praise or to blame means nothing else than to impute to someone the malice or goodness of his action. Now an action is imputed to an agent, when it is in his power, so that he has dominion over it: because it is through his will that man has dominion over his actions, as was made clear above (Q[1], AA[1],2). Hence it follows that good or evil, in voluntary actions alone, renders them worthy of praise or blame: and in such like actions, evil, sin and guilt are one and the same thing.
Reply to Objection 1: Natural actions are not in the power of the natural agent: since the action of nature is determinate. And, therefore, although there be sin in natural actions, there is no blame.
Reply to Objection 2: Reason stands in different relations to the productions of art, and to moral actions. In matters of art, reason is directed to a particular end, which is something devised by reason: whereas in moral matters, it is directed to the general end of all human life. Now a particular end is subordinate to the general end. Since therefore sin is a departure from the order to the end, as stated above (A[1]), sin may occur in two ways, in a production of art. First, by a departure from the particular end intended by the artist: and this sin will be proper to the art; for instance, if an artist produce a bad thing, while intending to produce something good; or produce something good, while intending to produce something bad. Secondly, by a departure from the general end of human life: and then he will be said to sin, if he intend to produce a bad work, and does so in effect, so that another is taken in thereby. But this sin is not proper to the artist as such, but as man. Consequently for the former sin the artist is blamed as an artist; while for the latter he is blamed as a man. On the other hand, in moral matters, where we take into consideration the order of reason to the general end of human life, sin and evil are always due to a departure from the order of reason to the general end of human life. Wherefore man is blamed for such a sin, both as man and as a moral being. Hence the Philosopher says (Ethic. vi, 5) that "in art, he who sins voluntarily is preferable; but in prudence, as in the moral virtues," which prudence directs, "he is the reverse."
Reply to Objection 3: Weakness that occurs in voluntary evils, is subject to man's power: wherefore it neither takes away nor diminishes guilt.
Objection 1: It would seem that a human action is not meritorious or demeritorious on account of its goodness or malice. For we speak of merit or demerit in relation to retribution, which has no place save in matters relating to another person. But good or evil actions are not all related to another person, for some are related to the person of the agent. Therefore not every good or evil human action is meritorious or demeritorious.
Objection 2: Further, no one deserves punishment or reward for doing as he chooses with that of which he is master: thus if a man destroys what belongs to him, he is not punished, as if he had destroyed what belongs to another. But man is master of his own actions. Therefore a man does not merit punishment or reward, through putting his action to a good or evil purpose.
Objection 3: Further, if a man acquire some good for himself, he does not on that account deserve to be benefited by another man: and the same applies to evil. Now a good action is itself a kind of good and perfection of the agent: while an inordinate action is his evil. Therefore a man does not merit or demerit, from the fact that he does a good or an evil deed.
On the contrary, It is written (Isa. 3:10, 11): "Say to the just man that it is well; for he shall eat the fruit of his doings. Woe to the wicked unto evil; for the reward of his hands shall be given him."
I answer that, We speak of merit and demerit, in relation to retribution, rendered according to justice. Now, retribution according to justice is rendered to a man, by reason of his having done something to another's advantage or hurt. It must, moreover, be observed that every individual member of a society is, in a fashion, a part and member of the whole society. Wherefore, any good or evil, done to the member of a society, redounds on the whole society: thus, who hurts the hand, hurts the man. When, therefore, anyone does good or evil to another individual, there is a twofold measure of merit or demerit in his action: first, in respect of the retribution owed to him by the individual to whom he has done good or harm; secondly, in respect of the retribution owed to him by the whole of society. Now when a man ordains his action directly for the good or evil of the whole society, retribution is owed to him, before and above all, by the whole society; secondarily, by all the parts of society. Whereas when a man does that which conduces to his own benefit or disadvantage, then again is retribution owed to him, in so far as this too affects the community, forasmuch as he is a part of society: although retribution is not due to him, in so far as it conduces to the good or harm of an individual, who is identical with the agent: unless, perchance, he owe retribution to himself, by a sort of resemblance, in so far as man is said to be just to himself.
It is therefore evident that a good or evil action deserves praise or blame, in so far as it is in the power of the will: that it is right or sinful, according as it is ordained to the end; and that its merit or demerit depends on the recompense for justice or injustice towards another.
Reply to Objection 1: A man's good or evil actions, although not ordained to the good or evil of another individual, are nevertheless ordained to the good or evil of another, i.e. the community.
Reply to Objection 2: Man is master of his actions; and yet, in so far as he belongs to another, i.e. the community, of which he forms part, he merits or demerits, inasmuch as he disposes his actions well or ill: just as if he were to dispense well or ill other belongings of his, in respect of which he is bound to serve the community.
Reply to Objection 3: This very good or evil, which a man does to himself by his action, redounds to the community, as stated above.
Objection 1: It would seem that man's actions, good or evil, are not meritorious or demeritorious in the sight of God. Because, as stated above (A[3]), merit and demerit imply relation to retribution for good or harm done to another. But a man's action, good or evil, does no good or harm to God; for it is written (Job 35:6, 7): "If thou sin, what shalt thou hurt Him? . . . And if thou do justly, what shalt thou give Him?" Therefore a human action, good or evil, is not meritorious or demeritorious in the sight of God.
Objection 2: Further, an instrument acquires no merit or demerit in the sight of him that uses it; because the entire action of the instrument belongs to the user. Now when man acts he is the instrument of the Divine power which is the principal cause of his action; hence it is written (Is. 10:15): "Shall the axe boast itself against him that cutteth with it? Or shall the saw exalt itself against him by whom it is drawn?" where man while acting is evidently compared to an instrument. Therefore man merits or demerits nothing in God's sight, by good or evil deeds.
Objection 3: Further, a human action acquires merit or demerit through being ordained to someone else. But not all human actions are ordained to God. Therefore not every good or evil action acquires merit or demerit in God's sight.
On the contrary, It is written (Eccles. 12:14): "All things that are done, God will bring into judgment . . . whether it be good or evil." Now judgment implies retribution, in respect of which we speak of merit and demerit. Therefore every human action, both good and evil, acquires merit or demerit in God's sight.
I answer that, A human action, as stated above (A[3]), acquires merit or demerit, through being ordained to someone else, either by reason of himself, or by reason of the community: and in each way, our actions, good and evil, acquire merit or demerit, in the sight of God. On the part of God Himself, inasmuch as He is man's last end; and it is our duty to refer all our actions to the last end, as stated above (Q[19], A[10]). Consequently, whoever does an evil deed, not referable to God, does not give God the honor due to Him as our last end. On the part of the whole community of the universe, because in every community, he who governs the community, cares, first of all, for the common good; wherefore it is his business to award retribution for such things as are done well or ill in the community. Now God is the governor and ruler of the whole universe, as stated in the FP, Q[103], A[5]: and especially of rational creatures. Consequently it is evident that human actions acquire merit or demerit in reference to Him: else it would follow that human actions are no business of God's.
Reply to Objection 1: God in Himself neither gains nor losses anything by the action of man: but man, for his part, takes something from God, or offers something to Him, when he observes or does not observe the order instituted by God.
Reply to Objection 2: Man is so moved, as an instrument, by God, that, at the same time, he moves himself by his free-will, as was explained above (Q[9], A[6], ad 3). Consequently, by his action, he acquires merit or demerit in God's sight.
Reply to Objection 3: Man is not ordained to the body politic, according to all that he is and has; and so it does not follow that every action of his acquires merit or demerit in relation to the body politic. But all that man is, and can, and has, must be referred to God: and therefore every action of man, whether good or bad, acquires merit or demerit in the sight of God, as far as the action itself is concerned.