Preliminaries

Although it is quite common for scholars to refer to the problem of universals, this way of speaking is deceptive.

There are in fact a cluster of problems in the fields of logic, philosophy of language, epistemology, and metaphysics. Medieval philosophers speculated about universals in all these contexts. This article will focus primarily, but not exclusively, upon the ontological problems associated with universals. (For a survey of medieval discussions of uni-versals with an emphasis on the semantic and epistemological aspects, consult Klima 2008.)

Medieval philosophers developed their theories of universals in light of developments in late ancient philosophy. One important locus for the discussion of the nature and existence of universals was Aristotle’s Categories. In this work, Aristotle distinguished between two types of predication: ‘‘being said of some subject’’ or ‘‘being in some subject.’’ The items that are neither said of some subject nor are in some subject were interpreted to be individual substances. Everything else is predicated (Gr. kategoreisthai) of these individuals or the properties of these individuals. Aristotle’s analysis of the phrase ‘‘x is said of y’’, together with his claim in De interpretatione that the universal is that which is predicable of many (7,17a39-40), suggested to late ancient commentators that those items that were said of something were universals.

Late ancient commentators wondered what the subject matter of the Categories was. Were the predicables things, words, or concepts? In general, it was felt that since the Categories was a logical work, the treatise was primarily about words. But these words were meaningful; they somehow stood for or referred to things and the properties of things. The simplest way for a universal term to signify would be for it to signify a universal thing. Thus, for many interpreters, Aristotle’s logic implied the existence of universal things.

In his ‘‘Introduction’’ (Isagoge) to Aristotle’s logic, Porphyry claimed that there were five basic types of universal predications: the genus, the species, the differentia, the proprium, and the accident. But Porphyry famously refused to determine whether universality applies to anything besides words. He began his Isagoge by announcing that he would not address three questions, since they belonged to a deeper inquiry (1.9-14, [trans. Spade 1994:1]). First, he would not consider whether universals ‘‘subsist’’ - that is, exist outside the mind - or whether they only manifest in bare conceptions. Second, he would not consider whether they are corporeal or incorporeal, if they subsist. Third, he would not consider whether they exist separately or subsist only in perceptible things.

Many medieval discussions of universals can be found in commentaries on Porphyry’s opening remarks. The Greek Neoplatonic commentators often used this text as an appropriate place to elaborate a threefold classification of the universal: (1) the universal before the many, (2) the universal in the many, and (3) the universal after the many. Latin-speaking philosophers prior to the end of the twelfth century did not know this classification of the universal. However, it was known in the medieval Arabic world, and the scheme was picked up by many later Latinspeaking philosophers.

In the medieval tradition, the universals before the many were identified with the Divine Ideas in God’s mind. They were the archetypes from which God created everything. No medieval philosopher denied the existence of the Divine Ideas. Hence, medieval philosophers never defended certain forms of anti-realism. No medieval philosopher would deny that abstract objects exist. Even thoroughgoing non-realists such as Abelard and Ockham believed in the existence of at least some forms, although these forms would be particulars.

The universals after the many were concepts in the human mind, often formed by a process of abstraction. Most medieval philosophers believed that these items were universals properly speaking, since they could be associated with many things.

From the ontological perspective, the main dispute among medieval philosophers was whether there is any mind-independent thing or reality that is common to many individuals - that is, whether there are any univer-sals in re. For something to be a universal in re, it would seem that it must be present simultaneously and as a whole in each of many individuals in such a way that it contributes to the substance of each individual (cf. Boethius, In Isag. 2nd ed., I, 10, 161.16-19). Adam and Eve would not share a universal, essential constituent if they merely shared portions of that constituent in the way that they might share a cake, or if they shared all of it in the way that two people can each wholly own a horse (as when the first sells the horse to the other), or if they both participated in all of it as spectators each take in the whole play. But is it possible for any thing to be essentially and entirely present in many individuals at the same time? Many medieval philosophers - even many who are traditionally labeled ‘‘realists’’ - thought that this could not happen.