In this comment I wish to defend Antony Duff's final conclusion; namely, that punishment is to be seen as a deterrent system constrained by requirements of justice. I shall do this, however, mainly by using John Kleinig's arguments. My aim is to show that although Kleinig himself rejects deterrence as part of punishment's justification, some of his arguments can best be defended if deterrence is taken into account. In the final section of the comment I shall return to Duff's arguments in this context, but only in order to raise some doubts as to their underlying assumption.

Before doing so, let me compare, briefly, Duff's and Kleinig's attitudes which seem to be relevant to the purpose of this comment.

Both Kleinig and Duff believe that, ideally, punishment is to be justified by retributive considerations. According to Kleinig, even in such an imperfect society as ours, punishment should still remain retributive.