BACKGROUND

The ‘problem of universals’, central in mediaeval philosophy, derived from commentaries on Aristotle written by Porphyry and Boethius, both of whom injected Platonist themes into their expositions. The problem concerned the nature of things predicated of many particulars as common to them. How can one entity (a unity) be common to many individuals? What foundation is there in distinct particulars for a common predicate? A more fundamental question concerned the order of metaphysical priority between concrete particulars and universals. Several notions of priority were expressed in the criteria for substances listed by Aristotle. What are the ultimate subjects of predication? What are the entities on which the existence of others depends? What is unchangeable and capable of definition, as subjects of necessary truths and scientific knowledge are supposed to be? Scholastic Aristotelians answered these questions in terms of the doctrine of categories. Individuals in the category of substance (primary substances) meet the first two criteria, and species that exist in primary substances, considered universally (secondary substances), meet the last criterion. In contrast, Neoplatonists gave priority (substantiality) on all three counts to abstract entities that have a mode of existence independent of, and apart from, particulars that resemble them more or less imperfectly. Elements from both traditions were retained in the seventeenth century. But the formulation of issues and the range of acceptable positions were radically changed by the anti-Aristotelian thrust of mechanism. This section sketches the background of this refocusing.