Suppose an enemy demands from a city the surrender for execution of an innocent man on pain of the burning of the city and the destruction of its inhabitants. May the city cut off that member for the safety of the whole body politic, as a person may cut off his own hand to save his life? The state has not dominion over the life of a citizen, nevertheless it may kill a citizen in punishment of crime, because the punishment is useful to the whole people, is for the common good, is preservative of the social life. Why, however, should the state be permitted to kill a criminal rather than an innocent man, since it has no dominion over the life of either, and we suppose the death of each is necessary for the public good? If you answer by saying a man may cut off a diseased member but not a sound one to save his body, and the state in like manner may cut off a criminal, unsound member, but not an innocent one, this answer does not remove the difficulty: we may cut off even a sound member to save the body. Suppose, for example, a man caught by the arm and in danger of death from a flood; he might sever a sound arm to escape death if no other means presented. In like manner the state might cut off an innocent, sound member to save its life from the enemy, as described above.
This reasoning, however, is open to objection. The state has no dominion over the life of its members, and there is a vast difference between the members of the human body and those of a body politic. A member of a human body has no right in itself against the other members; nor is it capable of natural injury, since it is not separable from the whole suppositum, or person. The suppositum, or person, has a right to the use of the members; it alone is injured when a member is amputated; and the members are solely for the utility of the suppositum. Therefore we may licitly destroy a member to save the suppositum for which this member exists.
The state, however, is not a suppositum in this sense; it may not wrest the life of its members to its own utility, because the citizens are not for the state; on the contrary, the state is for them and their utility. That a rational being should be for the utility of another person or a society makes him a slave and supposes dominion in the user. A slave is differentiated from a subject by the fact that the subject is only politically governed--that is, governed for his own utility and good; the slave is governed despotically--that is, for the utility and good of his master. The state may not, as a master, use the life of a subject for its own utility alone. Although the suppositum does not own its members, yet since the members are not separable from the man, are not self-centred as are the citizens in a state, the man may use them for his own utility. They are as slaves under a master, not as subjects in a body politic; therefore they may be sacrificed for the good of the suppositum.