Retributive justification. Why should wrongdoers be punished? Most people might respond simply that they deserve it or that they should suffer in return for the harm they have done. Such feelings are deeply ingrained, at least in many cultures, and are often supported by notions of divine punishment for those who disobey God's laws. A simple retributivist justification provides a philosophical account corresponding to these feelings: someone who has violated the rights of others should be penalized, and punishment restores the moral order that has been breached by the original wrongful act. The idea is strikingly captured by Immanuel Kant 's claim that an island society about to disband should still execute its last murderer. Society not only has a right to punish a person who deserves punishment, but it has a duty to do so. In Kant's view, a failure to punish those who deserve it leaves guilt upon the society; according to G. W. F. Hegel, punishment honors the criminal as a rational being and gives him what it is his right to have. In simple retributivist theory, practices of punishment are justified because society should render harm to wrongdoers; only those who are guilty of wrongdoing should be punished; and the severity of punishment should be proportional to the degree of wrongdoing, an approach crudely reflected in the idea of "an eye for an eye, a tooth for a tooth."
So, the reason for punishment is the maximization of welfare, and punishment should be of whomever, and of whatever form and severity, are needed to meet that goal. This may sometimes justify punishing the innocent, or inflicting disproportionately severe punishments, when that will have the best consequences overall (perhaps executing a few suspected shoplifters live on television would be an effective deterrent to shoplifting, for instance). It also suggests that punishment might turn out never to be right, depending on the facts about what actual consequences it has.