Whether in some cases it may be lawful to maim anyone?

Objections

Objection 1 : It would seem that in no case can it be lawful to maim anyone. For Damascene says (De Fide Orth. iv, 20) that "sin consists in departing from what is according to nature, towards that which is contrary to nature." Now according to nature it is appointed by God that a man's body should be entire in its members, and it is contrary to nature that it should be deprived of a member. Therefore it seems that it is always a sin to maim a person.
Objection 2 : Further, as the whole soul is to the whole body, so are the parts of the soul to the parts of the body (De Anima ii, 1). But it is unlawful to deprive a man of his soul by killing him, except by public authority. Therefore neither is it lawful to maim anyone, except perhaps by public authority.
Objection 3 : Further, the welfare of the soul is to be preferred to the welfare of the body. Now it is not lawful for a man to maim himself for the sake of the soul's welfare: since the council of Nicea [*P. I, sect. 4, can. i] punished those who castrated themselves that they might preserve chastity. Therefore it is not lawful for any other reason to maim a person.