From Constitutional Necessities to Causal Necessities∗

Humeans and non-Humeans commonly and reasonably agree that there may be necessary connections (“necessities”, for short) between entities that are identical—e.g., Hesperus and Phosphorus, water and H2O—or merely partly distinct—e.g., sets and their individual members, fusions and their individual parts, instances of determinates and determinables, members of certain natural kinds and certain of their intrinsic properties, and (especially among physicalists) certain physical and mental states. Humeans maintain, however, as per “Hume’s Dictum”, that there are no necessary connections between entities that are wholly distinct;1 and in particular, no necessary causal connections between such entities (even when the background conditions requisite for causation are in place). The Humean’s differential treatment appears principled, in reflecting that commonly accepted necessary connections involve constitutional relations (involving, roughly, existential ontological dependence between certain entities), whereas wholly distinct entities (notably, causes and effects) do not constitute each other in this sense. I’ll argue, however, that the appearance of principle is not genuine, as per the following conditional: