Parts of Universals: An Essay on Aristotle's Categories

In De Interpretatione 7, Aristotle defines the universal as “that which is by its nature (πέφυκε) predicated of (κατηγορεῖσθαι) a number (πλειόνων) of things” (17a39-40). Unfortunately, this definition of the universal is not terribly informative. One obvious question it leaves unanswered is this: what sort of entity satisfies it? This definition tells us how universals behave, but it doesn’t tell us what universals are.

My dissertation proposes a novel interpretation of Aristotle according to which a universal is a whole or composite object. The species Man, for example, is a whole whose parts are the various individual human beings in the world: Socrates, Callias, and so on. Likewise, the genus Animal is a whole whose parts are its sub-species (e.g., Man, Horse, and so on) and, by transitivity, the individual animals falling under those sub-species.

As I read him, Aristotle is a mereological pluralist. In Metaphysics Δ.25 and Δ.26, he identifies a different kinds of parts and different kinds of wholes. Thus, the way in which a universal is a whole is not like the way in which a tree or a lizard is a whole. To say that the species Man is a whole, then, is not to say that the species Man relates to individual men the way that a tree relates to its leaves and branches. Having argued that Aristotle takes universals to be wholes, I attempt to articulate the differences between universals thus understood and more familiar composite entities like trees. Then I defend this view from a series of objections both historical and contemporary.

I put this account of universals to metaphysical work in interpreting the Categories. For example, Aristotle claims (2a13-15) that that in addition to primary substances like Socrates and Bucephalus, there are also secondary substances: the species and genera of primary substances. I defend a novel view called criterial pluralism, according to which there are two reasons why the species and genera of primary substances qualify as substances. First, they are underlying subjects of predication, and so in some sense ontologically fundamental (albeit less ontologically fundamental than the primary substances of which they are composed). Second, they reveal what primary substances are, making them epistemologically fundamental as well: they are the route through which we achieve genuine knowledge of primary substances.

Aristotle recognizes the existence of non-substantial entities in addition to substances. Some of these entities he describes as individual (ἂτομον) and numerically one (ἓν ἀριθμῷ). These non-substantial individuals are things such as my knowledge of English grammar, the sweetness of this piece of candy, or the redness of this can of soda. Are such items particulars or universals? That is, are such items capable of belonging to multiple subjects or not? I defend the traditional view that non-substantial individuals are particulars. I show how the account of universals given above can alleviate some of the chief textual difficulties for this traditional view.

Not only does Aristotle recognize the existence of both substantial and non-substantial entities, he thinks that certain substantial entities – the primary substances – are ontologically fundamental: “if the primary substances did not exist it would be impossible for any of the other things to exist” (2b5-6).” It has been difficult to make sense of this passage, primarily because it seems as though the converse is true as well. I defend a novel account of the ontological fundamentality of primary substances according to which they are in some sense the cause of being (14b10-23) of other entities. I claim that we can understand the notion of causation at work here by analogy to Aristotle’s account of material causation in Physics II. A material cause is “that out of which a thing comes to be (τὸ ἐξ οὗ γίνεταί) and which persists” (194b24-26). Since I have argued that universals are wholes, primary substances are in a sense that out of which secondary substances come to be, and non-substantial individuals are in a sense that out of which non-substantial universals come to be. Together with the claim that non-substantial individuals are particulars, this gives us an account of the ontological fundamentality of primary substances over all other entities in the Categories ontology.