Section III. On the Killing of an Unjust Aggressor

I. It is lawful to repel an unjust aggressor against life, even, with the necessary conditions posited, by killing him. This is clear from Sacred Scripture¹ and from the doctrine of the Church contained in the old Law.² And indeed what prevents me from repelling unjust force by force, if otherwise it cannot be repelled? Or: what prevents me from returning like for like to him who is on the point of inflicting unjust harm on me, if otherwise the damage cannot be averted? For the rest, if the proposition were denied, sufficient provision would not have been made for the security of life (St. Alphonsus, III, 380).

Nor is it an obstacle that the one attacked, by killing the attacker, seems to prefer his own temporal life to the eternal life of his neighbor, since we are bound only to give life for a neighbor who is placed in extreme spiritual necessity. But the attacker is not placed in extreme spiritual necessity, because he can rescue himself from necessity by ceasing from the attack. In a word: his spiritual necessity is voluntary, and therefore not extreme (St. Alphonsus, III, 380).

I said: it is lawful, because a man is not bound to use an extraordinary means, of which sort is the killing of one's neighbor, for saving life. Indeed it is even an act of charity "to permit one's own killing, lest another be deprived of temporal and eternal life" (St. Alphonsus, loc. cit.). Make an exception, however, if the life of the one attacked is necessary or quasi-necessary to the community or family.

I said: with the necessary conditions posited. Moreover, the conditions required so that it may be lawful to kill an aggressor against life are: 1. that the aggression be unjust; 2. that the aggression be physical; 3. that the moderation of blameless defense be observed. It is said:

1. That the aggression be unjust; this is clear. Thus it is not lawful to kill an executioner who carries out a sentence of death. Yet it suffices that it be materially unjust, for example if it is done by a madman, by a drunk person, and so forth. The reason is that a right, in this case the right to life, by its nature can be defended absolutely or always without injustice; without any sin, if charity does not stand in the way. But charity stands in the way only in the case in which the one attacked is in the state of grace, while the aggressor, for example a drunk person, is morally certainly in the state of mortal sin, and therefore, in the posited hypothesis, is placed in extreme spiritual necessity (St. Alphonsus, III, 390).

2. That the aggression be physical; for the negation of this condition would give occasion to delusions and would gravely harm public order. Thus it does not suffice, for example, that another has merely decided on or threatened aggression; that someone persuades or orders an attack on you; that a judge pronounces an unjust sentence against you. Hence proposition 18 was rightly condemned by Alexander VII: it is lawful to kill a false accuser, false witnesses, and even a judge from whom an unjust sentence certainly threatens, if an innocent person cannot avoid damage in another way³ (St. Alphonsus, III, 388). Yet it suffices that the aggression has begun in some way; therefore it is not required, for example, that the enemy already aim a gun, but it suffices that he take up arms to kill you at once (St. Alphonsus, III, 387).

3. That the moderation of blameless defense be observed, as it is usually said, that is, that in defending oneself one not proceed beyond necessity. Thus it is not lawful to kill an aggressor if the one attacked can flee or by beating or wounding rescue himself from danger of death. But if he cannot flee without great dishonor, which nevertheless today generally has no place unless perhaps you except a military man, especially one constituted in a higher rank, he is not bound to flight (St. Alphonsus, III, 381). And generally it is not evident that one attacked who is bound to flight is bound to it from justice. Moreover, observe that those who in the case, especially of a sudden attack, exceed in their own defense are easily excused from grave sin, namely because of disturbance of mind and lack of time for deliberating.

¹ Exod. 22:2.

² Chapter Significasti nobis (18, book 5, Decretals, title 12); chapter Si perfodiens (3, book 5, title 12); the single Clementine De homicidio, etc. Civil laws agree.

³ Denzinger-Bannwart, n. 1118.

II. What is lawful for preserving life is also lawful for preserving the integrity of members, for forestalling grave wounding, for preserving chastity, and for acquired goods of fortune of great importance.¹ Namely, the said goods are regarded as sufficiently grave goods, which may be defended by any force whatever, even lethal, if there is need, against an unjust aggressor. But the same is not lawful for protecting honor and reputation. These indeed are more grave than goods of fortune; but, besides the fact that honor and reputation can generally be defended in another way, the faculty of defending them by death would open the way to delusions and innumerable killings. Hence proposition 30 was condemned by Innocent XI: "It is lawful for an honorable man to kill an attacker who strives to inflict calumny, if otherwise this ignominy cannot be avoided; the same also must be said if someone strikes with the open hand or beats with a stick, and after the open-hand blow or blow of the stick flees."² Yet one is not bound to permit another by deed, for example by a blow, to assail one's honor; he can therefore repel ignominious treatment and, if the other then proceeds further, oppose force (St. Alphonsus, III, 313, 386; 381).

¹ As regards goods which are either of lesser importance or are not yet possessed, note the propositions condemned by Innocent XI. Proposition 31: regularly I can kill a thief for the preservation of one gold coin (Denzinger-Bannwart, n. 1181). Proposition 32: it is lawful to defend by killing-defense not only the things which we actually possess, but also those to which we have an inchoate right and which we hope to possess (Denzinger-Bannwart, n. 1182). Proposition 33: it is lawful both for an heir and for a legatee to defend himself in such a way against one unjustly impeding either the entering upon an inheritance or the payment of legacies; likewise also for one having a right to a chair or prebend against one unjustly impeding possession of them (Denzinger-Bannwart, n. 1183).

² Denzinger-Bannwart, n. 1180.

III. Finally, it is lawful, even by killing the aggressor, to defend the life, integrity of members, chastity, and great goods of one's neighbor; and indeed the life and integrity of members, whether the neighbor dissents from or consents to the killing or mutilation of himself; for since he is not the master of life and members, his consent is invalid. It is generally not lawful to defend the chastity and goods of one's neighbor in this way if the neighbor consents to the one attacking. I said generally, because it is lawful for him upon whom disgrace or damage redounds to defend even the one who consents to his own damage (St. Alphonsus, III, 389, 391).

IV. Generally there is no obligation of defending one's neighbor by killing, because charity does not oblige one to such a burden. Make an exception: 1. if the common good requires it; 2. if the neighbor is very near, namely a parent, child, spouse, or brother (St. Alphonsus, III, 390).

Question. Whether it is lawful to kill an unjust aggressor directly, or only indirectly.

Resp. Several teach that an unjust aggressor can be killed only indirectly. Namely, they judge that the killing of the aggressor is lawful insofar as it is lawful to place the act of defending oneself; from this act a double effect follows, one's own preservation, which is intended, and the killing of the aggressor, which is permitted. Thus Cajetan¹ and Billuart.²

Others defend the contrary, and it seems one must adhere to them. For it is lawful by the consent of all to place an act of defending oneself, for example the discharge of a gun. But sometimes an act is defensive of oneself only insofar as it is killing of the aggressor. Therefore it is lawful to place the act insofar as it is killing of the aggressor. But this is nothing other than to take the killing of the aggressor as a means, or to kill the aggressor directly.

Objection. The defended opinion is contrary to the doctrine of St. Thomas.

Resp. St. Thomas (II-II, q. 64, a. 7), at first glance, seems to oppose our opinion; for he reasons, in order to prove that the killing of an unjust aggressor is lawful, from an act with a double effect, of which one, namely the preservation of life, is intended, while the other, namely the death of one's neighbor, happens outside the intention. But if you suppose that, according to the mind of St. Thomas, only that which is sought as an end is properly intended, but not that which is only assumed as a means, the holy Doctor is not opposed to us. But that this is wrongly supposed is not proved; hence there remains doubt for me about what St. Thomas judges (cf. St. Alphonsus, Homo Apostolicus, tract 8, n. 12).

¹ Commentary on II-II, q. 64, a. 7.

² De tractatu de iure et iustitia, dissertation 10, article 5.