ARTICLE II: On the Killing of an Aggressor

733. Things to be noted beforehand. An aggressor can be just or unjust. - There is no treatment of a just aggressor; since it is not licit to kill, mutilate, or strike him, because it is repugnant that rights opposed to rights be given. Whence one justly condemned to punishment cannot defend himself against the ministers of justice, such as lictors, witnesses, judges, executioners, by striking, mutilating, etc. (cf. n. 2311; see German Code, 226-231). An unjust aggressor is called one who, right resisting, actually invades life, fortune, modesty, or honor.

734. Principles. I. For protecting one's own life, or members of the body, it is licit to kill an unjust aggressor, with the moderation of blameless defense nevertheless observed.¹ That such defense of oneself is licit by both human and divine law, all doctors with St. Thomas and the Roman Catechism affirm, and the same is expressly declared in c. Si vero 3, de sent. excom., where it is said: "All laws and all rights permit force to be repelled by force" (III, 380; H. Ap., VIII, 11).

Indeed, if someone were morally certain concerning an aggression prepared for him, and could not otherwise avoid the ambushes laid and the dangers of death, it would be licit for him to anticipate the aggressor, lest later his own defense be rendered impossible or ineffective. Yet St. Alphonsus admonishes (III, n. 387) that this opinion, although more probable, can scarcely be held in practice because of the danger of hallucination.²

We have said: 1. It is licit to kill, but no one is held to this; because it is an extraordinary means of conserving one's own life.

Indeed, it is an act of perfection to permit one's own killing, lest the aggressor be deprived of temporal life together with eternal life; provided that: a) the life of the one invaded is not necessary or very useful to the common good, or to the family; b) the one invaded is not in the state of mortal sin: because then he is altogether held to defend himself (III, 380; H. Ap., VIII, 12, where there are more things). See what was said n. 482, 483.

2. An unjust aggressor, even if he is mad or drunk. For drunkenness and madness indeed exempt the aggressor, of themselves, from sin, but they do not deprive the one invaded of the right of protecting his own life. - In practice defense becomes easier if the aggressor is mad or drunk.

3. With moderation observed, etc.; that is, there must be in defense such moderation that nothing is done beyond that which is absolutely necessary for warding off injury. Whence, if the one invaded had another way of freeing himself from the invader, for example by fleeing, terrifying him with cries, disarming him, wounding him, he would not be in the extreme necessity which alone furnishes a just cause of killing.

But this, that they flee, etc., cannot be imposed on those who, because of omission of positive defense, even with lethal outcome, would receive a mark of cowardice or timidity. Yet this does not run for clerics, religious, and common people, for whom flight is not ignominious. - For the rest, the killing or mutilation of the aggressor must never be done from hatred, etc. Yet if it were done from hatred, the sin of injustice would not be present. Finally it must be noted that there is no moderation in defense if someone attacks, pursues, and kills the aggressor who flees.

735. • II. For protecting temporal goods of great value, it is licit to kill an unjust aggressor, provided they cannot otherwise be defended. Thus commonly.³ It is proved from Exodus (22, 2): If a thief breaking into a house, or digging under it, should be found, and having received a wound should die: the striker is not guilty of blood. The stronger reason is because the precept of charity does not oblige one to prefer the goods of neighbor of a higher order, unless neighbor is in extreme necessity. But he is not in extreme necessity when he of his own accord exposes himself to danger of death (III, 382). Besides, the killing of such an aggressor is not against justice, which of itself rather favors the rights of the actual possessor, and shows it to be necessary that such repression be done, so that the goods which are necessary for life may be preserved.

We have said: 1. Goods of great value, whose loss namely would bring notable harm, which must be judged from the circumstances, with both the wealth or need of the person and the necessity or superfluity of the things themselves being inspected.

For it is certain that it is not licit to kill an aggressor if it is a question of goods of small moment; or of goods which we do not yet actually possess. Hence this 31st proposition was condemned by Innocent XI: "Regularly I can kill a thief for the conservation of one gold coin." And the 32nd: "Not only is it licit to defend by killing defense the things which we actually possess, but also those things to which we have an inchoate right, and which we hope that we shall possess" (III, 383, q. 2; H. Ap., VIII, 15).

2. Provided they cannot otherwise be defended: for otherwise it must be said if, through the laws and police of the State, sufficient provision is made for public security and the reparation of injuries (Marres, de Just., l. 2, n. 240).

From these things it is deduced: a) It is licit for each person to defend his goods with arms, even through servants. - b) If a thief has already placed in safety your thing of great value which was taken away, and you have no other way of recovering it, you can more probably, if the thief resists you demanding back the thing, strike him, and, if necessary, kill him; because he is still an invader of the thing and a true aggressor. - c) Since the right of defense is natural, it belongs also to clerics and religious, who then do not incur irregularity. Yet such defense is not to be advised to them, if it is a question of goods of fortune alone (III, n. 383-385). d) Of itself it would not be illicit to arrange certain machines for defending a house against malefactors. For what the owner can do through himself, in the act of aggression, he can do through others or through other things. - Ordinarily, however, these will not be licit, because for the most part moderation in defense will be lacking. But if they become necessary, let citizens be warned that danger is not lacking. Ami du Cl., 1905, p. 1146; cf. Lehmkuhl, Cas. consc., n. 670.

736. III. For protecting modesty, it is licit to kill an unjust invader, if force cannot otherwise be repelled. Thus commonly against a few. The reason is both because for the most part there is danger of consenting to an act of sin, and because modesty is a good to be esteemed most greatly, and to be preferred to all riches, indeed even to life (III, 386; H. Ap., VIII, 16).

Hence: 1. A man can kill him who wishes to commit adultery with his wife, if he cannot otherwise avoid infamy (l. El. qq. ref., n. 22; III, 391).

2. It will be licit for a girl, not only while she is actually violently touched, but immediately after, to strike the invader with slaps, fists, a staff, and even with non-dangerous blows. The reason is that unless in such a mode she shows her displeasure, he will not easily depart. Hence, this is to be advised to a woman, so that the other at least may come to his senses and not solicit her another time (III, 386).

737. IV. For protecting the goods of reputation or honor, it is not licit, at least practically speaking, to kill an unjust aggressor. This is established from proposition 30 condemned by Innocent XI: "It is right for an honored man to kill an invader who strives to inflict calumny, if otherwise this calumny cannot be avoided; the same also must be said if someone strikes with a slap or beats with a staff, and after the slap struck or the blow of the staff flees." For the one invaded can always provide for his own honor by another way, for example by flight, by action before a tribunal. Besides, this being admitted, the way would be open to innumerable slayings (III, 381; 2. El. qq. ref., n. 9).

Although it is not licit to kill the invader of honor, nevertheless by no right is it prohibited that the one invaded immediately by words or deeds make an attack against those who by words or deeds detracted from his honor. Certainly there are counsels and the example of the Lord which indicate another way; but here the question is only of licit or illicit (Noldin, II, n. 334).

Let it be noted: 1. What is licit for anyone for the defense of his own life, modesty, fortune, this also generally is LICIT for the defense of similar goods against an unjust invader of neighbor, as is gathered from the precept of loving neighbor as oneself. Except, as regards modesty, the case in which the person invaded herself consents: unless she is very near to the defender, and he cannot otherwise avoid his own infamy. - But if it is a question of life, it is licit to defend neighbor, even if this person has yielded the right of legitimate defense; because the right to defense is diverse from the right to life: for neighbor cannot abdicate the right to life, since he is not the lord of his own life.

2. No one is HELD to such defense of neighbor, unless he owes it from office, as soldiers hired for the security of citizens; or from piety toward more nearly related blood relatives, namely parents, children, brothers, sisters. The reason is that from the precept of charity alone we are not held to stain our hands with human blood, nor to undergo grave inconveniences which usually arise from homicide otherwise licit. - Yet except "if the one to be killed by the invader is drunk and in the state of mortal sin, because he is truly in extreme necessity of soul" (III, n. 389-391; H. Ap., VIII, 17).

3. Civil laws do not protect the goods enumerated above in an equal way. Let each person consult the codes. Nevertheless tribunals ordinarily do not condemn those who kill an aggressor of goods of the greatest moment. Cf. Tanquerey, II, p. 144; Noldin, II, n. 334; Olshausen, Strafgesetzbuch, § 53.