 Whether Mill’s claims about the importance of secondary principles imply rule utilitarianism depends, in part, on whether he wants to define right action in terms of the best set of secondary principles or whether they are just a reliable way of doing what is in fact best. If he defines right action in terms of conformity with principles with optimal acceptance value, then he is a rule utilitarian. But if the right action is the best action, and secondary principles are just a reliable (though imperfect) way of identifying what is best, then Mill is an act utilitarian. Mill appears to address this issue in two places. In Chapter II of Utilitarianism Mill appears to suggest that in the case of abstinences or taboos the ground of the obligation in particular cases is the beneficial character of the taboo considered as a class (II 19). But in a letter to John Venn Mill claims that the moral status of an individual action depends on the utility of its consequences; considerations about the utility of a general class of actions are just defeasible evidence about what is true in particular cases (CW XVII: 1881). Unfortunately, natural readings of the two passages point in opposite directions on this issue, and each passage admits of alternative readings.