Renewing a Modal Account of Existential Dependence: Upcycling Mackie’s INUS Condition for Causation.

Abstract

Relations of existential dependence are pervasive in metaphysics and science when we inquire about the nature of objects - what they are like, and about their existence – whether or not they are. We may think wholes depend on parts, living things depend on carbon molecules and ecosystems depend on plants and animals. In some sense, the former depends for its existence on the latter and will not exist without that which it depends on. A traditional approach has been to appeal to modal definitions to answer the question, ‘what is the relation of ontological dependence?’ where the salient feature of a modal definition of ontological dependence is metaphysical necessity, such that where x depends on y, x cannot exist without y. For instance, when a composite object exists then its parts must exist too. This analysis has been deemed by many to be too coarse-grained, resulting in misclassified dependence relations making modal definitions incompatible with metaphysical theories that posit necessary objects or necessary connections between wholly distinct objects. One example would be a theory that says numbers necessarily exist. It can never be false that the number three exists, but when electricity exists or wooden tables exists, so does the number three. However, we do not wish to say there is dependence between the existence of these objects. Any two objects like sets that have only one member and that sole member, that always coexist will, falsely, appear to share a mutual dependence relation between them. Many contemporary metaphysicians have instead followed Kit Fine’s essential existential dependence which has required the ideological primitive of an essence. Then we can say that there is nothing in the essence of an object that would require say, a number for its existence. I argue that we need not follow Fine in making the heavyweight ontological commitment to essences and instead, I propose a renewed modal account of existential dependence that draws inspiration from a neglected account of causation. I argue that we can lean on the framework of causal theories in developing the formal treatment of existential dependence since both causal and existential dependence relations share in their logical/structural properties, and both are important for backing theories of explanation. From this suggestive analogy I draw between existential dependence and causation, it is my view that we should explore the INUS framework for causation produced by J. L. Mackie who claimed that causes were a necessary part of a minimally and jointly sufficient set of actual conditions. Despite the many problems this theory faces as a theory for causation, as the basis for a theory of existential dependence, the INUS account shows to be quite promising in responding to the familiar problems that beset traditional modal-existential accounts. On this view, I claim that where x depends on y, y is a non-redundant part of a minimal situationally-sufficient condition for x. By appeal to situation theory, objects do not depend on one another at the level of possible worlds where necessary connections are instantiated, and necessarily existing objects exist. On my account, the dependee is a necessary part of a situation that minimally sufficient for the existence of the dependent object.