I believe I can resolve the debate on whether punishments like imprisonment and the death penalty violate the unalienable rights to life and liberty (Letters, Shannon Johnson, April 11, and Richard E. Shipman, March 21).

Actually, there is only one unalienable right: the right to be free from aggression, the initiation of force. The unalienable rights to life and liberty are two applications of that basic right. Murder is an initiation of force against a person's life, kidnapping and slavery against a person's liberty, and theft against a person's property. They have a common thread under justice: Such actions entail an initiation of force against the person.

Defensive force is also force against another person. However, it is not aggression but a response to it. When we kill attackers who threaten our lives, we don't violate any unalienable right of theirs, for we are not violating their right to be free from the initiation of force. Instead, we are protecting our right to be free from that force. Similarly, punishment is a response to aggression, not an initiation of force. Defense and punishment (commensurate with the aggression) do not violate the aggressor's unalienable right to be free from the initiation of force.

Regarding the death penalty, Mr. Shipman worried about imposing it upon innocent people. Mrs. Johnson replied, "Once the verdict is given, the rights of law-abiding citizens must take precedence over the supposed rights of the criminal." Mrs. Johnson misses the point. Corollary to the unalienable right to be free from the initiation of force is the unalienable obligation not to initiate force. Even if convicted, the innocent are not in fact criminals. Having given them due process does not excuse us. By punishing them, we have not only violated their unalienable right to be free from the initiation of force, we have violated our obligation not to use such force.

We are not obligated under rights to impose punishment; we are obligated to avoid aggression. If we imprison someone unjustly, we can repay our debt to that person to some extent and beg forgiveness. But how do we compensate the innocent dead? Given the fallibility of human beings, this is a fundamental ethical problem for capital punishment.