 The central question to ask about any supposed criterial inference is whether we understand the nature of the phenomena mentioned in the premise and conclusion to be necessarily caught up with other, but not in such a way that the presence of either entails the other. If A is a criterion of B, then it’s a necessary truth that A is evidence for, or counts toward, B—so says Anthony Kenny in speaking of a criterion in the sense intended here. If a criterion is understood in this way—and the term is certainly being used in a technical, non-everyday sense if it is—there’s a fair amount of intuitive appeal to the claim that pain behavior is a criterion for being in pain. Our understanding of what pain and pain behavior are seems to connect the two necessarily. That’s true even if no one in pain ever exhibits pain behavior, or everyone exhibits pain behavior when not in pain. (Admittedly, the scenarios for either state of affairs would be very strange. Neither is impossible, though.) Likewise, although every act of lying could turn out to be right, and every act of non-lying turn out to be wrong, our understanding of what wrongness and lying are is such that the latter necessarily counts toward the former. On the other hand, our understanding of drinking arsenic and dying—of what they are—isn’t such that drinking arsenic is criterial for dying. It’s not that our understanding of dying is somehow necessarily caught up with the idea of drinking arsenic the way it is in the pain-pain behavior and lying-wrongness cases. Even if every time a person drank arsenic he died, and every time a person died he had drunk arsenic, the connection between the two is purely inductive.