The Internal Unity of Natural Kinds

Abstract

It is often assumed that the essence of a natural kind is complex, being such as to include (or to wholly consist of) multiple fundamental properties. For instance, perhaps the essence of the kind “electron” includes both negative charge and a precise rest mass, where neither of these is derivable from the other, nor derivable from some other foundational property. This assumption raises the ‘unity problem’: how to explain what unifies or holds together these properties. One important answer is developed by David Oderberg. His model draws on insights from both analytic metaphysics and the Scholastic tradition. I provide a summary of his solution to the unity problem and point to a potential worry it faces. I conclude by adverting to an alternative solution that would still fit within Oderberg’s overall system.