Section — Wouters, Manual of Moral Theology
Scholion. On Mutilation and Beating of a Criminal
I. Public authority, just as it can kill a criminal, so a fortiori can mutilate, imprison, and beat him. But it is another question whether public authority lawfully imposes certain mutilations, namely vasectomy, oophorectomy, and so forth, as a punishment. Now, speaking theoretically, a punishment of this kind, although it can be defended from the fact that it deprives criminals of a great good, that is, of the faculty of procreating, seems less congruent with the common sense of morality. I said theoretically, because in practice it will impose the said punishment for this end, that the procreation of offspring to be procured by the criminal may be impeded. But that is illicit, because it is not lawful even for public authority directly to impede the good of the species (n. 740).
II. Superiors lacking supreme power, for example parents and those taking their place, cannot mutilate or strictly imprison their delinquent subjects; nevertheless they can beat them moderately. It is said:
They cannot mutilate them, because "man himself and all his parts" belong to society (St. Thomas, II-II, q. 65, a. 1); but it belongs only to the supreme governor of society to subtract from the community what pertains to the community (n. 741).
They cannot strictly imprison them, because not only man and all his parts belong to the community, but also his activity; hence again it belongs only to the supreme governor of society to impede the activity of man by strict imprisonment (St. Thomas, II-II, q. 65, a. 3). Nevertheless inferior Superiors can keep their subjects at home for just causes.
They can beat them moderately. For they enjoy the power of coercing subjects insofar as by acting thus they do not inflict injury on the community. But beating a subject inflicts no injury on the community, because it removes neither life, nor the integrity of members, nor activity (St. Thomas, II-II, q. 65, a. 2). Yet it is not lawful for a man to beat his wife, unless a most grave necessity urges, since the wife is not his servant but his companion (St. Alphonsus, VI, 972).
III. Equals, for example brothers and sisters, even if older by birth, cannot even beat delinquents, unless by consent of a superior. The reason is that by beating some harm is inflicted on the body of him who is beaten; moreover, it is not lawful to inflict harm on someone except by way of punishment, on account of justice. But no one can punish someone unless he is subject to his power. Therefore an equal cannot beat an equal (St. Thomas, II-II, q. 65, a. 2).