Chapter III. Justifiable Homicide

IN defence of my own life from unjust attack I may use whatever violence is necessary and even go to the length of killing the aggressor, if I cannot otherwise save my life. This right of self-defence all laws, human and divine, concede, as Innocent III declared. Nature herself teaches us that an act which is necessary for self-defence is lawful, and even if it lead to the taking of the life of the unjust aggressor it does not cease to be lawful. A higher value must be set on the life of the innocent than on that of the guilty, especially when the guilty one is the cause of his life being put in jeopardy. No one is justified in using greater violence than is necessary for the purpose of self-defence,so that if by striking or wounding an assailant of my life I can effectually defend myself, I am not justified in killing him. On the same principle no private person can take vengeance for violence which has already been done, by offering violence in return; vindictive justice is reserved for public authority, at any rate in more serious matters. Nor may one whose life is threatened anticipate the attack; defence is only lawful when the attack is practically being made or is at any rate imminent. Unless the attack is practically imminent it is always possible to resort to other means than homicide for the defence of one’s own life; one may invoke the protection of the law or at least fly the intending assailant.

Under the same limitations it is lawful to kill the assailant not only of one’s life, but also of limb, of chastity, and of property. For all these goods belonging to an innocent person may be lawfully defended by him even at the cost of the life of the unjust assailant of them, who is responsible for his own death by his unwarrantable action. When it is said that we may kill an unjust assailant in defence of property, it is supposed that the property which is threatened is of considerable amount. Innocent XI condemned a proposition which asserted that, “As a rule I may kill a thief for the preservation of a gold piece.” This proposition is false, for a rich man would not be justified in shooting a thief whom he saw walking off with one of his silver spoons. If, however, the thief threatens property of considerable value—say, twenty pounds or so—and the only way of saving the money is by taking the life of the thief, this would be lawful. Moreover, when a highwayman demands my purse or my life, I am not bound to hand him my purse, even though it contain little money; I may always defend myself from such unjust attacks, even though it finally involves the death of the aggressor.

It is not lawful to kill another who attacks my honour with insulting words. The contrary used to be held by some theologians, but the doctrine was condemned by Alexander VII and Innocent XI. The reason of the difference between this case and the foregoing is that verbal insults are often not of very serious consequence; they are better and more effectively met by quiet contempt than by being taken seriously, and that would be a perilous doctrine which taught that a man might avenge an insult with the death of the offender. What constitutes an insult is often a very subjective question, and the results of the doctrine would be deplorable.

What one may lawfully do, that, as a rule, another may help him to do; and so I may kill or maim an unjust assailant not only of my own life, limb, chastity, or property, but when any innocent person is similarly threatened I may also do the same in his defence. Although I may lawfully do this, yet there is seldom an obligation of doing it, for the obligation would only arise from charity, and as we saw above, this virtue does not usually bind with such serious inconvenience as would always be involved in taking life in defence of another. Those who have charge of the public peace and security are more strictly bound to perform their duty of protecting life and property even at the sacrifice of the lives of wrongdoers.