Utilitarianism and deontological ethics have traditionally dominated the debate about the justification of punishments and have thereby been associated respectively with the theories of deterrent and retributivist punishment. Nowadays, the debate about the justification of punishment is increasingly dominated by mixed theories.

Most of these mixed theories represent the attempt of deontological philosophers, that is, mainly those influenced by Kant, to break with the traditional conception of the deontological, that is, the rather Kantian justification of punishment, as a purely retributive theory. Such theories were actually – with good reason – suspected of resting more on private morality than on legal principles.

In what follows, I will assess the success of these attempts to strengthen the Kantian retributivist theory through the integration into the justification of punishment of an element of some form of deterrence or prevention. First, I hope to show that these attempts are only superficially mixed, whereas in reality they are completely based on a retributive foundation. Secondly, I will inquire into the arguments that Kant employs to justify the principle of retribution and the type of retribution he adopts, and attempt to determine the weaknesses of this argument. Finally, I will propose a principle of punishment that, in my opinion, fits in better with Kant's principle of right than his own conception of punishment. In so doing, I will consciously and consistently employ Kant's principle of right as a criterion for judging the correctness of that principle of punishment.