Why would anyone be interested in John Duns Scotus today? I argue that Scotus' theory of common natures answers the contemporary problem of universals by denying that universals are needed either to explain real resemblances between things or to explain causation. As I note below, contrary to leading contemporary interpreters of Aristotle, Scotus' reading of Aristotelian natures implies that they cannot be universal. Yet, he does not fall into nominalism from denying the reality of universals. His common natures are neither universal nor particular, but occupy a third way "between" universality and particularity. They can occupy that position, I argue, because while universality and singularity are accidents to them, indifference to universality and singularity is necessary to them. Although I use Scotus to address a contemporary metaphysical problem, I emphasize his distance from the framework of contemporary metaphysical debate: his discussion of natures is outside the framework of events, objects and properties. Scotus, like Aristotle, assumes the framework of a constituent ontology: essence is not a property or a set of properties of that to which it belongs. Further, he adopts a substance ontology that cannot be happily cast within the framework of four dimensionalism. Nevertheless, I show how a cogent case can be made for Scotus' substance ontology and explain how it fits with and is required by his theory of common natures.
