A.N. Prior’s (1960) famous counterexamples to ethical autonomy involve cases where nonnormative premises entail a normative conclusion. Consider, for example, a normative claim N and a non-normative claim M. If N v M is non-normative, then the non-normative ~M & (N v M) entails the normative N. If the disjunction is normative, then it is entailed by the non-normative M. The entailments are impe...

In this paper, we tackle the study of so-called supplementarity measures. They are introduced axiomatically and are then related to incompatibility measures by antonyms. To do this, we have to establish what we mean by antonymous measure. We then prove that, under certain conditions, supplementarity and incompatibility measures are antonymous. Besides, with the aim of constructing antonymous me...