Numerous philosophical theories purport to justify a system of legal punishment. It is doubtful, however, that any of them successfully answer these three questions: Why punish? Whom to punish? How much to punish? Straightforward retributive theories, which justify punishment by looking back at the wrongful harm done by an offender, don’t adequately answer the question of why the offender should be harmed in return for harm done. More sophisticated retributive theories construe punishment as equalizing an unfair advantage taken by an offender. Such theories have difficulty with the question of how much to punish. Consent theories view offenders as willing punishment onto themselves by their voluntary acts. The various versions of this theory all fail to answer one or more of the three questions: why, whom, and how much. Rights forfeiture theories give a question-begging answer to the “why” question and don’t answer the question of how much. Consequentialist theories, which justify punishment by looking forward to results such as deterrence and incapacitation, have difficulties with whom to punish and how much. Arguably, punishing an innocent person who is believed to be guilty could deter potential offenders, and a serious offense might be deterred by a less severe punishment than a minor offense. Some philosophers see insurmountable problems for strictly backward-looking theories that appeal to guilt of the offender and for strictly forward-looking theories that appeal to future consequences. The solution, then, could be a theory that appeals to future results to provide a reason for punishing, but looks back at harm done by the offender to answer the question of whom to punish and how much. However, without a unifying rationale for taking these different approaches to these particular issues, such a mixed theory would be ad hoc if not incoherent.
In recent decades, philosophers have offered several approaches that might avoid the pitfalls described above by providing a unified rationale for punishment that is both backward and forward looking. Self-defense theories hold that it is rational and justifiable for the state to threaten punishment in order to defend citizens against offenses. They then move by various strategies from the justifiability of the threat to the justifiability of punishment. Forced choice theories justify punishment as a way of distributing necessary harm to the guilty rather than the innocent. Censure theories attempt to justify punishment as the state’s means of expressing disapproval of offenses against the law. Each of these theories faces difficulties, but proponents might judge that even though they haven’t yet been able to adequately state the justification of punishment, their theory is on the right track. Others view the difficulties faced by all theories and boldly conclude that punishment is not justifiable. There is little support for rehabilitation as an alternative to punishment. The practices associated with restorative justice, although not directly aimed at punishment, typically involve punishment, so they still require a justification for punishment. Whether a system of restitution could take the place of a system of punishment is problematic. The situation is made even more troublesome by the fact that the theories that have been surveyed aim to justify punishment in a society with a just political structure and laws. Even if such a theory succeeds, it is far from clear that it would justify punishment in a society where many of those who are harmed by punishment have also been victims of injustice.