Question Fourth. On the Killing of an Unjust Aggressor

332. On the right against an aggressor of life. It is licit for anyone to defend both his own life and the life of others, even with the killing of an unjust aggressor, provided the moderation of blameless defense is observed. This is both because everyone has the right of preferring his own life to the life of an unjust aggressor, and because otherwise criminals, with the greatest damage to human society, would affect others with injuries. Therefore all laws and all positive rights permit force to be repelled by force, even if from defense of oneself the death of the aggressor follows.¹

a. An aggressor is called one who is already actually attacking or actually does certain things from which he is morally judged already to be attacking, for example, he is already preparing weapons; for if physical aggression had to be awaited, defense of oneself would often become impossible. Nevertheless, it is not licit, by preventing the aggression, to kill one who lays snares and will certainly attack later, although it is impossible to escape the danger.² It is not licit after the aggression to kill the aggressor, because that would not be defense but vengeance.

b. Where the required conditions are present, anyone can defend himself against any unjust aggressor, even with the death of the aggressor, whether the aggression is formally or materially unjust. Wherefore even a son can defend himself against a father, a subject against a ruler, unless greater evils such as wars are to be feared, a layman against a cleric, a cleric against a layman, and anyone even against a furious, insane, or drunken person. For although here he commits only material injustice, nevertheless the right to life is not lost through the insanity or drunkenness of the aggressor.

c. It is licit for anyone to defend his own life in this way, but no one is bound to kill an unjust aggressor; wherefore he can licitly permit his own killing, for this means of preserving life is hard and cruel, from which nature recoils. Yet in a twofold case it is not licit to permit one's own killing: alpha. if the life of the one attacked is either necessary or very useful to the common good; beta. if the one attacked is in a state of mortal sin.

d. It is licit to defend in this way not only one's own life, but also the life of others; for what someone licitly does by himself, he can also do through another. Indeed, by reason of charity, piety, or office, this ought sometimes also to be done by those who are hired to protect the life or goods of others. But because such killing ordinarily brings great inconveniences with it, a private person is rarely bound to this, unless a reason of piety or office is added.

Therefore if the one attacked were a person necessary to the public good, or if he were father or son or wife, legal justice or piety would obligate one to defend his life. And those who are hired for the defense of others, such as soldiers and guards, are bound to defend the life of others even with their own grave inconvenience, because office obligates them to this.

e. If the one attacked knows that the aggressor is in a state of mortal sin, ordinarily he can defend himself even by killing the aggressor. For if the aggressor is formally unjust, he freely exposes himself to this danger; therefore since he himself can provide for himself, he is not in extreme spiritual necessity. But if he is materially unjust, as an insane person, in fact he is in extreme spiritual necessity and only the one attacked can assist him. Hence if the one attacked prudently judged himself to be in a state of grace, and moreover knew certainly that the aggressor was in a state of mortal sin which he would afterward amend, charity would demand that he prefer the aggressor's eternal salvation to his own temporal life. But since this twofold knowledge cannot be had, this obligation scarcely ever certainly exists; and an uncertain obligation cannot deprive another of the certain right of defending himself.

¹ C. Si vero 3, De sententia excom. (V, 39).

² Cf. proposition 18 condemned by Alexander VII.

333. On the right against an aggressor of goods. 1. It is licit to defend not only life, but also other goods of greater importance of an inferior order, even with the killing of the unjust aggressor, if they cannot be preserved in another way. For charity does not oblige that one prefer another's goods of a higher order to his own goods of a lower order, unless the other is in extreme necessity. But the unjust aggressor of another's good is not in extreme necessity, since he voluntarily exposes himself to the danger of death.¹

That even goods of fortune can be licitly defended with the killing of an unjust aggressor, theologians have always rightly inferred from sacred Scripture, which permits the killing of a nocturnal thief breaking into a house.²

2. But the goods which it is licit to defend in this way, with the moderation of blameless defense observed, are:

a. Goods of fortune of great importance. These goods must be of great importance, because charity prohibits that on account of a light damage the gravest damage be inflicted upon a neighbor.³

alpha. Goods of great importance are not only those which, if taken away, would leave someone lacking sustenance for himself and his own, but also those whose loss would be a notable damage according to the quality of the person.

beta. It is licit to kill a thief taking away a thing of great importance, if the thing cannot be recovered in another way and if, after warning, he is unwilling to let it go; but if warning is impossible or useless, it also can be omitted.⁴

gamma. It is not licit to kill one who takes away a thing of small importance; but it is licit to protect it against the thief and to recover it once taken away by the thief if it cannot be recovered otherwise with sufficient certainty. But if the thief employs force, where there is need he can even be killed. For in that case he is not killed to protect or recover the thing, but to defend one's own person.⁵

b. Chastity: for if it is licit to kill the aggressor of goods of fortune, a fortiori it is licit to kill the aggressor of chastity, which is a good more excellent than riches. Nevertheless a virgin is not bound to kill the aggressor of chastity, but can passively submit, because chastity is not lost against the will.

c. Integrity of members: for what is licit for preserving life is also licit for defending integrity of body.

¹ St. Alphonsus, n. 383.

² Ex. 22:2; St. Thomas, II-II, q. 64, a. 7.

³ Proposition 31 condemned by Innocent XI: Regularly I can kill a thief for the preservation of one gold coin.

⁴ St. Alphonsus, n. 382; Bucceroni, Casus consc.^5, n. 59, 3.

⁵ Ballerini-Palmieri, II, n. 890.

334. On the aggressor of honor. According to the law of perfection handed down to us by Christ, injuries received are to be borne equanimously and forgiven to the enemy without satisfaction; but according to the order of justice and natural equity, these things seem able to be established:¹

a. It is not licit to kill the aggressor of reputation or honor either to impede an imminent injury or to recover honor taken away.

For this is prohibited by the first part of condemned proposition 30,² and rightly indeed, because rarely are the conditions required for bloody defense present, such as that grave damage be inflicted and that there be no other way of repairing the damage. But if the required conditions are present, nevertheless this is not licit because the moderation of blameless defense is not observed; for to recover honor taken away by verbal, indeed even real injury, according to the moral estimation of men, the killing of the aggressor is not required. Rather the retorsion of the injury suffices, even, if there is need, with the striking of the calumniator, where honor cannot be recovered through a judge.

b. It is licit to recover honor taken away by real or verbal injury by immediately inflicting an equal injury, if, as ordinarily happens, it cannot be recovered through a judge without trouble.

Therefore it is licit immediately to strike back at one who ignominiously struck someone, not indeed for the sake of vengeance, but to avoid infamy or to recover honor, where in the moral estimation of men the one struck is judged deprived of honor until he has struck back, but, on the contrary, to have recovered honor if he has struck back. Likewise it is licit to return a similar name to him who called someone by a disgraceful name. Nor should it be said that this opinion has been condemned, since only this is condemned: that one striking can be killed if he flees. Practically, however, this opinion involves a twofold danger: lest the striking back be done for the sake of vengeance, and lest the moderation of blameless defense be violated. Moreover, if the one struck back wishes to strike again, nothing prevents the second striking from being impeded, even with drawn sword, if there is need.

c. It is not licit to recover honor taken away before by real or verbal injury by killing or striking the one who took it away.

For this is prohibited by the second part of condemned proposition 30, because the killing would not be defense but vengeance. Moreover, punishment for a committed offense must be inflicted by a judge.

Note. It must be observed that by positive law he who kills an aggressor of honor, chastity, or goods of fortune is considered as a homicide to be punished; only for impeding rape can a woman by civil law kill the aggressor.

¹ Cf. Elbel-Bierbaum, Theol. mor., I, pr. 4, n. 67 ss.; Genicot, Casus conscient., I, p. 154 s.; Viva, Theses damnatae, in prop. 30 condemned by Innocent XI, n. IX.

² It is licit for an honorable man to kill an aggressor who tries to bring calumny, if otherwise this ignominy cannot be avoided; the same also must be said if someone strikes a slap or strikes with a staff and after the inflicted slap or blow of the staff flees.

335. On the moderation of blameless defense. The moderation of blameless defense, which must be observed in defense of oneself, requires that nothing be done against the life of the aggressor unless it is necessary for protecting one's own life; for what necessity does not excuse is against justice. Therefore it requires three things: a. that life not be attacked unless the aggression is actually, morally, at hand; b. that the life of the aggressor not be attacked if the danger can be avoided in another way, such as by crying out or fleeing; c. that the aggressor not be killed if his wounding suffices for defense.

a. He is not bound to flee who cannot flee without great detriment, because, for example, he would incur the disgrace of a timid and cowardly man; for the moderation of blameless defense does not require that the danger of the aggressor be avoided with the greatest detriment to oneself. Therefore the following are bound to flee if they can do so safely enough: alpha. common men, because they suffer no loss of honor; beta. clerics and religious, because for them, who ought to furnish an example of meekness, flight is not disgraceful; gamma. all, even noble and military men, if the aggressor is drunk or insane, because in this case flight is disgraceful to no one.

b. Practically, judgment concerning the means necessary for the defense of oneself must be committed to the judgment of him whose life is in danger. But if someone in sudden danger, where time is lacking for weighing all circumstances, seizes a means which would not have been plainly necessary, he is not to be blamed.