Duns Scotus on Common Natures and Carving at the Joints of Reality

Despite the puzzles of interpretation it engenders, John Duns Scotus’s theory of common natures is widely cited as an example of scholastic “realism.” Common natures serve a variety of functions in Scotus’s system, providing the “real unity” which serves as the subject for Aristotelian science. The “proper passions” of substances – characteristics which serve to identify substances by type, but do not formally belong to the essence of a subject – are ontologically dependent on common natures according to kind. And Scotus operates on the assumption that it is the description of created subjects according to their common natures which is the most fundamental description of them.Thus, for Scotus, common natures and their relations determine what we might call the “structure” of reality.

But not every “subject of a science” is a common nature. According to Scotus, “being,” the subject of “metaphysics,” does not have the same real unity as the natural groupings under the ten categories of Aristotle. As a consequence of this, the “transcendental passions of being” include predicates which do not possess the “real unity” of a common nature, because they are too abstract or generic to do so. I will undertake three primary tasks in this dissertation. First, I will provide a description of the role of common natures in Scotus’s system. Then, I will discuss the rule or criterion by which Scotus posits common natures to account for certain cases of univocal predication – as opposed to cases of univocal predication for which he doesn’t posit common natures. Ultimately, I will discuss the difference between two types of “structure” in Scotus’s system: the case of distinct “quidditative components” in the essence of a subject, and the case of a subject and its passion. In both cases, the relata are “formally distinct.” In the former case but not the latter, they are related by “act-potency composition.” Ultimately, common natures explain the structure in the created world, but not every relatum in a structural relation is a common nature.