Thomas Aquinas: Summa Theologiae (excerpt, part 6)

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Part II.2, Question 40, Article 1: Whether it is always sinful to wage war?

Objection 1: It would seem that it is always sinful to wage war. Because punishment is not inflicted except for sin. Now those who wage war are threatened by Our Lord with punishment, according to Mt. 26:52: "All that take the sword shall perish with the sword." Therefore all wars are unlawful.

Objection 2: Further, whatever is contrary to a Divine precept is a sin. But war is contrary to a Divine precept, for it is written (Mt. 5:39): "But I say to you not to resist evil"; and (Rm. 12:19): "Not revenging yourselves, my dearly beloved, but give place unto wrath." Therefore war is always sinful.

Objection 3: Further, nothing, except sin, is contrary to an act of virtue. But war is contrary to peace. Therefore war is always a sin.

Objection 4: Further, the exercise of a lawful thing is itself lawful, as is evident in scientific exercises. But warlike exercises which take place in tournaments are forbidden by the Church, since those who are slain in these trials are deprived of ecclesiastical burial. Therefore it seems that war is a sin in itself.

On the contrary: Augustine says in a sermon on the son of the centurion: "If the Christian Religion forbade war altogether, those who sought salutary advice in the Gospel would rather have been counselled to cast aside their arms, and to give up soldiering altogether. On the contrary, they were told: 'Do violence to no man ... and be content with your pay.' If he commanded them to be content with their pay, he did not forbid soldiering."

I answer that: In order for a war to be just, three things are necessary. First, the authority of the sovereign by whose command the war is to be waged. For it is not the business of a private individual to declare war, because he can seek for redress of his rights from the tribunal of his superior. Moreover it is not the business of a private individual to summon together the people, which has to be done in wartime. And as the care of the common weal is committed to those who are in authority, it is their business to watch over the common weal of the city, kingdom or province subject to them. And just as it is lawful for them to have recourse to the sword in defending that common weal against internal disturbances, when they punish evil-doers, according to the words of the Apostle (Rm. 13:4): "He beareth not the sword in vain: for he is God's minister, an avenger to execute wrath upon him that doth evil"; so too, it is their business to have recourse to the sword of war in defending the common weal against external enemies. Hence it is said to those who are in authority (Ps. 81:4): "Rescue the poor: and deliver the needy out of the hand of the sinner"; and for this reason Augustine says (Contra Faust. xxii, 75): "The natural order conducive to peace among mortals demands that the power to declare and counsel war should be in the hands of those who hold the supreme authority."

Secondly, a just cause is required, namely that those who are attacked, should be attacked because they deserve it on account of some fault. Wherefore Augustine says (Questions. in Hept., qu. x, super Jos.): "A just war is wont to be described as one that avenges wrongs, when a nation or state has to be punished, for refusing to make amends for the wrongs inflicted by its subjects, or to restore what it has seized unjustly."

Thirdly, it is necessary that the belligerents should have a rightful intention, so that they intend the advancement of good, or the avoidance of evil. Hence Augustine says (De Verb. Dom.): "True religion looks upon as peaceful those wars that are waged not for motives of aggrandizement, or cruelty, but with the object of securing peace, of punishing evil-doers, and of uplifting the good." For it may happen that the war is declared by the legitimate authority, and for a just cause, and yet be rendered unlawful through a wicked intention. Hence Augustine says (Contra Faust. xxii, 74): "The passion for inflicting harm, the cruel thirst for vengeance, an unpacific and relentless spirit, the fever of revolt, the lust of power, and such like things, all these are rightly condemned in war."

Reply to Objection 1: As Augustine says (Contra Faust. xxii, 70): "To take the sword is to arm oneself in order to take the life of anyone, without the command or permission of superior or lawful authority." On the other hand, to have recourse to the sword (as a private person) by the authority of the sovereign or judge, or (as a public person) through zeal for justice, and by the authority, so to speak, of God, is not to "take the sword," but to use it as commissioned by another, wherefore it does not deserve punishment. And yet even those who make sinful use of the sword are not always slain with the sword, yet they always perish with their own sword, because, unless they repent, they are punished eternally for their sinful use of the sword.

Reply to Objection 2: Such like precepts, as Augustine observes (De Serm. Dom. in Monte i, 19), should always be borne in readiness of mind, so that we be ready to obey them, and, if necessary, to refrain from resistance or self-defense. Nevertheless it is necessary sometimes for a man to act otherwise for the common good, or for the good of those with whom he is fighting. Hence Augustine says (Ep. ad Marcellin. cxxxviii): "Those whom we have to punish with a kindly severity, it is necessary to handle in many ways against their will. For when we are stripping a man of the lawlessness of sin, it is good for him to be vanquished, since nothing is more hopeless than the happiness of sinners, whence arises a guilty impunity, and an evil will, like an internal enemy."

Reply to Objection 3: Those who wage war justly aim at peace, and so they are not opposed to peace, except to the evil peace, which Our Lord "came not to send upon earth" (Mt. 10:34). Hence Augustine says (Ep. ad Bonif. clxxxix): "We do not seek peace in order to be at war, but we go to war that we may have peace. Be peaceful, therefore, in warring, so that you may vanquish those whom you war against, and bring them to the prosperity of peace."

Reply to Objection 4: Manly exercises in warlike feats of arms are not all forbidden, but those which are inordinate and perilous, and end in slaying or plundering. In olden times warlike exercises presented no such danger, and hence they were called "exercises of arms" or "bloodless wars," as Jerome states in an epistle.

Part II.2, Question 64, Article 1: Whether it is unlawful to kill any living thing?

Objection 1: It would seem unlawful to kill any living thing. For the Apostle says (Rm. 13:2): "They that resist the ordinance of God purchase to themselves damnation." Now Divine providence has ordained that all living things should be preserved, according to Ps. 146:8,9, "Who maketh grass to grow on the mountains ... Who giveth to beasts their food." Therefore it seems unlawful to take the life of any living thing.

Objection 2: Further, murder is a sin because it deprives a man of life. Now life is common to all animals and plants. Hence for the same reason it is apparently a sin to slay dumb animals and plants.

Objection 3: Further, in the Divine law a special punishment is not appointed save for a sin. Now a special punishment had to be inflicted, according to the Divine law, on one who killed another man's ox or sheep (Ex. 22:1). Therefore the slaying of dumb animals is a sin.

On the contrary: Augustine says (De Civ. Dei i, 20): "When we hear it said, 'Thou shalt not kill,' we do not take it as referring to trees, for they have no sense, nor to irrational animals, because they have no fellowship with us. Hence it follows that the words, 'Thou shalt not kill' refer to the killing of a man."

I answer that: There is no sin in using a thing for the purpose for which it is. Now the order of things is such that the imperfect are for the perfect, even as in the process of generation nature proceeds from imperfection to perfection. Hence it is that just as in the generation of a man there is first a living thing, then an animal, and lastly a man, so too things, like the plants, which merely have life, are all alike for animals, and all animals are for man. Wherefore it is not unlawful if man use plants for the good of animals, and animals for the good of man, as the Philosopher states (Polit. i, 3).

Now the most necessary use would seem to consist in the fact that animals use plants, and men use animals, for food, and this cannot be done unless these be deprived of life: wherefore it is lawful both to take life from plants for the use of animals, and from animals for the use of men. In fact this is in keeping with the commandment of God Himself: for it is written (Gn. 1:29,30): "Behold I have given you every herb ... and all trees ... to be your meat, and to all beasts of the earth": and again (Gn. 9:3): "Everything that moveth and liveth shall be meat to you."

Reply to Objection 1: According to the Divine ordinance the life of animals and plants is preserved not for themselves but for man. Hence, as Augustine says (De Civ. Dei i, 20), "by a most just ordinance of the Creator, both their life and their death are subject to our use."

Reply to Objection 2: Dumb animals and plants are devoid of the life of reason whereby to set themselves in motion; they are moved, as it were by another, by a kind of natural impulse, a sign of which is that they are naturally enslaved and accommodated to the uses of others.

Reply to Objection 3: He that kills another's ox, sins, not through killing the ox, but through injuring another man in his property. Wherefore this is not a species of the sin of murder but of the sin of theft or robbery.

Part II.2, Question 64, Article 2: Whether it is lawful to kill sinners?

Objection 1: It would seem unlawful to kill men who have sinned. For our Lord in the parable (Mt. 13) forbade the uprooting of the cockle which denotes wicked men according to a gloss. Now whatever is forbidden by God is a sin. Therefore it is a sin to kill a sinner.

Objection 2: Further, human justice is conformed to Divine justice. Now according to Divine justice sinners are kept back for repentance, according to Ezech. 33:11, "I desire not the death of the wicked, but that the wicked turn from his way and live." Therefore it seems altogether unjust to kill sinners.

Objection 3: Further, it is not lawful, for any good end whatever, to do that which is evil in itself, according to Augustine (Contra Mendac. vii) and the Philosopher (Ethic. ii, 6). Now to kill a man is evil in itself, since we are bound to have charity towards all men, and "we wish our friends to live and to exist," according to Ethic. ix, 4. Therefore it is nowise lawful to kill a man who has sinned.

On the contrary: It is written (Ex. 22:18): "Wizards thou shalt not suffer to live"; and (Ps. 100:8): "In the morning I put to death all the wicked of the land."

I answer that: As stated above (Article [1]), it is lawful to kill dumb animals, in so far as they are naturally directed to man's use, as the imperfect is directed to the perfect. Now every part is directed to the whole, as imperfect to perfect, wherefore every part is naturally for the sake of the whole. For this reason we observe that if the health of the whole body demands the excision of a member, through its being decayed or infectious to the other members, it will be both praiseworthy and advantageous to have it cut away. Now every individual person is compared to the whole community, as part to whole. Therefore if a man be dangerous and infectious to the community, on account of some sin, it is praiseworthy and advantageous that he be killed in order to safeguard the common good, since "a little leaven corrupteth the whole lump" (1 Cor. 5:6).

Reply to Objection 1: Our Lord commanded them to forbear from uprooting the cockle in order to spare the wheat, i.e. the good. This occurs when the wicked cannot be slain without the good being killed with them, either because the wicked lie hidden among the good, or because they have many followers, so that they cannot be killed without danger to the good, as Augustine says (Contra Parmen. iii, 2). Wherefore our Lord teaches that we should rather allow the wicked to live, and that vengeance is to be delayed until the last judgment, rather than that the good be put to death together with the wicked. When, however, the good incur no danger, but rather are protected and saved by the slaying of the wicked, then the latter may be lawfully put to death.

Reply to Objection 2: According to the order of His wisdom, God sometimes slays sinners forthwith in order to deliver the good, whereas sometimes He allows them time to repent, according as He knows what is expedient for His elect. This also does human justice imitate according to its powers; for it puts to death those who are dangerous to others, while it allows time for repentance to those who sin without grievously harming others.

Reply to Objection 3: By sinning man departs from the order of reason, and consequently falls away from the dignity of his manhood, in so far as he is naturally free, and exists for himself, and he falls into the slavish state of the beasts, by being disposed of according as he is useful to others. This is expressed in Ps. 48:21: "Man, when he was in honor, did not understand; he hath been compared to senseless beasts, and made like to them," and Prov. 11:29: "The fool shall serve the wise." Hence, although it be evil in itself to kill a man so long as he preserve his dignity, yet it may be good to kill a man who has sinned, even as it is to kill a beast. For a bad man is worse than a beast, and is more harmful, as the Philosopher states (Polit. i, 1 and Ethic. vii, 6).

Part II.2, Question 64, Article 3: Whether it is lawful for a private individual to kill a man who has sinned?

Objection 1: It would seem lawful for a private individual to kill a man who has sinned. For nothing unlawful is commanded in the Divine law. Yet, on account of the sin of the molten calf, Moses commanded (Ex. 32:27): "Let every man kill his brother, and friend, and neighbor." Therefore it is lawful for private individuals to kill a sinner.

Objection 2: Further, as stated above (Article [2], ad 3), man, on account of sin, is compared to the beasts. Now it is lawful for any private individual to kill a wild beast, especially if it be harmful. Therefore for the same reason, it is lawful for any private individual to kill a man who has sinned.

Objection 3: Further, a man, though a private individual, deserves praise for doing what is useful for the common good. Now the slaying of evildoers is useful for the common good, as stated above (Article [2]). Therefore it is deserving of praise if even private individuals kill evil-doers.

On the contrary: Augustine says (De Civ. Dei i): "A man who, without exercising public authority, kills an evil-doer, shall be judged guilty of murder, and all the more, since he has dared to usurp a power which God has not given him."

I answer that: As stated above (Article [2]), it is lawful to kill an evildoer in so far as it is directed to the welfare of the whole community, so that it belongs to him alone who has charge of the community's welfare. Thus it belongs to a physician to cut off a decayed limb, when he has been entrusted with the care of the health of the whole body. Now the care of the common good is entrusted to persons of rank having public authority: wherefore they alone, and not private individuals, can lawfully put evildoers to death.

Reply to Objection 1: The person by whose authority a thing is done really does the thing as Dionysius declares (Coel. Hier. iii). Hence according to Augustine (De Civ. Dei i, 21), "He slays not who owes his service to one who commands him, even as a sword is merely the instrument to him that wields it." Wherefore those who, at the Lord's command, slew their neighbors and friends, would seem not to have done this themselves, but rather He by whose authority they acted thus: just as a soldier slays the foe by the authority of his sovereign, and the executioner slays the robber by the authority of the judge.

Reply to Objection 2: A beast is by nature distinct from man, wherefore in the case of a wild beast there is no need for an authority to kill it; whereas, in the case of domestic animals, such authority is required, not for their sake, but on account of the owner's loss. On the other hand a man who has sinned is not by nature distinct from good men; hence a public authority is requisite in order to condemn him to death for the common good.

Reply to Objection 3: It is lawful for any private individual to do anything for the common good, provided it harm nobody: but if it be harmful to some other, it cannot be done, except by virtue of the judgment of the person to whom it pertains to decide what is to be taken from the parts for the welfare of the whole.

Part II.2, Question 64, Article 4: Whether it is lawful for clerics to kill evil-doers?

Objection 1: It would seem lawful for clerics to kill evil-doers. For clerics especially should fulfil the precept of the Apostle (1 Cor. 4:16): "Be ye followers of me as I also am of Christ," whereby we are called upon to imitate God and His saints. Now the very God whom we worship puts evildoers to death, according to Ps. 135:10, "Who smote Egypt with their firstborn." Again Moses made the Levites slay twenty-three thousand men on account of the worship of the calf (Ex. 32), the priest Phinees slew the Israelite who went in to the woman of Madian (Num. 25), Samuel killed Agag king of Amalec (1 Kgs. 15), Elias slew the priests of Baal (3 Kgs. 18), Mathathias killed the man who went up to the altar to sacrifice (1 Mach. 2); and, in the New Testament, Peter killed Ananias and Saphira (Acts 5). Therefore it seems that even clerics may kill evil-doers.

Objection 2: Further, spiritual power is greater than the secular and is more united to God. Now the secular power as "God's minister" lawfully puts evil-doers to death, according to Rm. 13:4. Much more therefore may clerics, who are God's ministers and have spiritual power, put evil-doers to death.

Objection 3: Further, whosoever lawfully accepts an office, may lawfully exercise the functions of that office. Now it belongs to the princely office to slay evildoers, as stated above (Article [3]). Therefore those clerics who are earthly princes may lawfully slay malefactors.

On the contrary: It is written (1 Tim. 3:2,3): "It behooveth ... a bishop to be without crime ... not given to wine, no striker."

I answer that: It is unlawful for clerics to kill, for two reasons. First, because they are chosen for the ministry of the altar, whereon is represented the Passion of Christ slain "Who, when He was struck did not strike" (1 Pt. 2:23). Therefore it becomes not clerics to strike or kill: for ministers should imitate their master, according to Ecclus. 10:2, "As the judge of the people is himself, so also are his ministers." The other reason is because clerics are entrusted with the ministry of the New Law, wherein no punishment of death or of bodily maiming is appointed: wherefore they should abstain from such things in order that they may be fitting ministers of the New Testament.

Reply to Objection 1: God works in all things without exception whatever is right, yet in each one according to its mode. Wherefore everyone should imitate God in that which is specially becoming to him. Hence, though God slays evildoers even corporally, it does not follow that all should imitate Him in this. As regards Peter, he did not put Ananias and Saphira to death by his own authority or with his own hand, but published their death sentence pronounced by God. The Priests or Levites of the Old Testament were the ministers of the Old Law, which appointed corporal penalties, so that it was fitting for them to slay with their own hands.

Reply to Objection 2: The ministry of clerics is concerned with better things than corporal slayings, namely with things pertaining to spiritual welfare, and so it is not fitting for them to meddle with minor matters.

Reply to Objection 3: Ecclesiastical prelates accept the office of earthly princes, not that they may inflict capital punishment themselves, but that this may be carried into effect by others in virtue of their authority.

Part II.2, Question 64, Article 5: Whether it is lawful to kill oneself?

Objection 1: It would seem lawful for a man to kill himself. For murder is a sin in so far as it is contrary to justice. But no man can do an injustice to himself, as is proved in Ethic. v, 11. Therefore no man sins by killing himself.

Objection 2: Further, it is lawful, for one who exercises public authority, to kill evil-doers. Now he who exercises public authority is sometimes an evil-doer. Therefore he may lawfully kill himself.

Objection 3: Further, it is lawful for a man to suffer spontaneously a lesser danger that he may avoid a greater: thus it is lawful for a man to cut off a decayed limb even from himself, that he may save his whole body. Now sometimes a man, by killing himself, avoids a greater evil, for example an unhappy life, or the shame of sin. Therefore a man may kill himself.

Objection 4: Further, Samson killed himself, as related in Judges 16, and yet he is numbered among the saints (Heb. 11). Therefore it is lawful for a man to kill himself.

Objection 5: Further, it is related (2 Mach. 14:42) that a certain Razias killed himself, "choosing to die nobly rather than to fall into the hands of the wicked, and to suffer abuses unbecoming his noble birth." Now nothing that is done nobly and bravely is unlawful. Therefore suicide is not unlawful.

On the contrary: Augustine says (De Civ. Dei i, 20): "Hence it follows that the words 'Thou shalt not kill' refer to the killing of a man -- not another man; therefore, not even thyself. For he who kills himself, kills nothing else than a man."

I answer that: It is altogether unlawful to kill oneself, for three reasons. First, because everything naturally loves itself, the result being that everything naturally keeps itself in being, and resists corruptions so far as it can. Wherefore suicide is contrary to the inclination of nature, and to charity whereby every man should love himself. Hence suicide is always a mortal sin, as being contrary to the natural law and to charity. Secondly, because every part, as such, belongs to the whole. Now every man is part of the community, and so, as such, he belongs to the community. Hence by killing himself he injures the community, as the Philosopher declares (Ethic. v, 11). Thirdly, because life is God's gift to man, and is subject to His power, Who kills and makes to live. Hence whoever takes his own life, sins against God, even as he who kills another's slave, sins against that slave's master, and as he who usurps to himself judgment of a matter not entrusted to him. For it belongs to God alone to pronounce sentence of death and life, according to Dt. 32:39, "I will kill and I will make to live."

Reply to Objection 1: Murder is a sin, not only because it is contrary to justice, but also because it is opposed to charity which a man should have towards himself: in this respect suicide is a sin in relation to oneself. In relation to the community and to God, it is sinful, by reason also of its opposition to justice.

Reply to Objection 2: One who exercises public authority may lawfully put to death an evil-doer, since he can pass judgment on him. But no man is judge of himself. Wherefore it is not lawful for one who exercises public authority to put himself to death for any sin whatever: although he may lawfully commit himself to the judgment of others.

Reply to Objection 3: Man is made master of himself through his free-will: wherefore he can lawfully dispose of himself as to those matters which pertain to this life which is ruled by man's free-will. But the passage from this life to another and happier one is subject not to man's free-will but to the power of God. Hence it is not lawful for man to take his own life that he may pass to a happier life, nor that he may escape any unhappiness whatsoever of the present life, because the ultimate and most fearsome evil of this life is death, as the Philosopher states (Ethic. iii, 6). Therefore to bring death upon oneself in order to escape the other afflictions of this life, is to adopt a greater evil in order to avoid a lesser. In like manner it is unlawful to take one's own life on account of one's having committed a sin, both because by so doing one does oneself a very great injury, by depriving oneself of the time needful for repentance, and because it is not lawful to slay an evildoer except by the sentence of the public authority. Again it is unlawful for a woman to kill herself lest she be violated, because she ought not to commit on herself the very great sin of suicide, to avoid the lesser sin of another. For she commits no sin in being violated by force, provided she does not consent, since "without consent of the mind there is no stain on the body," as the Blessed Lucy declared. Now it is evident that fornication and adultery are less grievous sins than taking a man's, especially one's own, life: since the latter is most grievous, because one injures oneself, to whom one owes the greatest love. Moreover it is most dangerous since no time is left wherein to expiate it by repentance. Again it is not lawful for anyone to take his own life for fear he should consent to sin, because "evil must not be done that good may come" (Rm. 3:8) or that evil may be avoided especially if the evil be of small account and an uncertain event, for it is uncertain whether one will at some future time consent to a sin, since God is able to deliver man from sin under any temptation whatever.

Reply to Objection 4: As Augustine says (De Civ. Dei i, 21), "not even Samson is to be excused that he crushed himself together with his enemies under the ruins of the house, except the Holy Ghost, Who had wrought many wonders through him, had secretly commanded him to do this." He assigns the same reason in the case of certain holy women, who at the time of persecution took their own lives, and who are commemorated by the Church.

Reply to Objection 5: It belongs to fortitude that a man does not shrink from being slain by another, for the sake of the good of virtue, and that he may avoid sin. But that a man take his own life in order to avoid penal evils has indeed an appearance of fortitude (for which reason some, among whom was Razias, have killed themselves thinking to act from fortitude), yet it is not true fortitude, but rather a weakness of soul unable to bear penal evils, as the Philosopher (Ethic. iii, 7) and Augustine (De Civ. Dei 22,23) declare.

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