In working out his theory of retributive punishment, Nozick argues that self-defense should be treated the same as or at least equivalent to punishment. Specifically, he claims that if a defender inflicts harm on an aggressor in order to thwart the aggression, the harm suffered should be deducted from the punishment that the aggressor deserves for his criminal act. To illustrate the point, let us suppose that the standard punishment for rape is seven years in jail. If the victim stymies the rape by cutting the attempting rapist with a razor blade, the pain that the offender suffers in the cutting should be deducted from the penalty a court may subsequently impose. The proper punishment will be seven years minus n, where n represents the harm inflicted in the victim's defensive effort to repel the rape. It is as though the injury is a ‘down payment’ on the penalty the offender deserves for his crime. As Nozick puts it: “One may, in defending oneself, draw against the punishment the attacker deserves…”.

Most people trained in the law would dismiss this claim out of hand. It is assumed that self-defense is one sort of thing and punishment, quite another. Self-defense expresses a right to defend oneself or others against aggression; its purpose is exclusively to prevent the threatened harm. Typically, punishment comes into play only after the aggressive act has made its mark – when it is too late for self-defense.