Aristotle begins his account of primary and secondary substances in chapter five of the
Categories with the claim that “a substance (ousia) – that which is called a substance most strictly, primarily (prôtôs), and most of all – is that which is neither said of a subject nor present in a subject” (2a11-13). Aristotle appeals to our linguistic intuitions about predication to tell us what the primary substances are. In a linguistic predication, there is a subject of predication and that which is predicated of a subject. But, to forestall a possible source of confusion: predication, as Aristotle conceives of it, is not merely a linguistic matter but also a matter of ontology. He thinks that when we predicate something of something (i.e., when we form subject-predicate sentences), we reveal (dêloi) something about something. More precisely, we reveal that something belongs (hyparchein) to something.35 So language is not a mere instrument for Aristotle – it reveals something about the way things are in the world. This suggests that there must be some sort of corresponding structure between the language we use and the way things are in the world.36
Now, in saying that primary substances are neither said of nor present in a subject, Aristotle identifies them with subjects themselves (hypokeimenon, lit. “that which stands
35 See De Interpretatione 4 and 5 (esp. 17a15 ff.).
36 Although it is reasonable to suggest that Aristotle (in so far as he insists that language or logos is revealing) is committed to the position that there exists an isomorphism between language and the world, it is important to notice that his commitment to such a position is not uncritical. As I will argue in the next section, Aristotle is well aware that the so-called subject criterion might not be the best guide for discovering primary substances. Thus, he seems to be aware that language is not a completely reliable guide to ontology.
under”).37 However, the fact that primary substances function as subjects does not yet
distinguish them from universals because Aristotle claims that secondary substances can likewise function as subjects: “As the primary substances stand to everything else, so the species and genera of the primary substances stand to all the rest: all the rest are predicated of these” (3a1-6; 2b17-20). Indeed, if it is insisted, for example, that a species (e.g. human being) can function only as predicate, not as subject, then in the very act of insisting on this one makes the species a subject of predication.
All Aristotelian commentators agree that the distinction between primary and secondary substances does not lie in the fact that primary substances are subjects
simpliciter, but rather in the fact that they are primary or ultimate or basic subjects. The idea that primary substances are ultimate subjects is in scholarly literature often called the “subject criterion”.38 Aristotle himself does not express this point explicitly, but he does seem to think that primary substances are called substances most strictly because “all the other things” are predicated of them, while they are not predicated of anything more basic. So primary substances are the only subjects in the ontology of the Categories
of which it is correct to assert that nothing stands under them. This seems to be the core insight that leads Aristotle to his famous position that “all the other things” require primary substances as basic subjects for their existence:
All the other things are either said of the primary substances as subjects or in them as subjects. This is clear from an examination of cases. For example, animal is predicated of human being and therefore also the particular human being (tinos anthrôpou); for were it
37 The subjecthood of the primary substances helps to explain why Tertullian and Augustine, and then Boethius and the medieval tradition following him chose to render ousia with substantia, rather than with essentia (which is what the morphology of Greek and Latin would suggest) – the role of the primary substance is to stand under (ld. substare) everything else.
predicated of none of the particular human beings it would not be predicated of human being at all. Again, colour is in body and therefore also in a particular body; for were it not in any of the particulars (kath’ hekasta) it would not be in body at all. Thus all the other things are either said of the primary substances as subjects or in them as subjects. So if the primary substances did not exist it would be impossible for any of the other things to exist (mê ousôn oun tôn proton ousiôn adynaton tôn allôn ti einai). (2a34-2b6)
Aristotle begins by claiming that everything which is not a primary substance is either said of and/or present in a primary substance. He tries to justify this claim on a case-by- case basis and argues that to predicate animal of human being is, ultimately, to predicate it of particular human beings for “were it predicated of none of the particular human beings it would not be predicated of human being at all”. From this Aristotle draws a famous conclusion that if the primary substances did not exist, then neither would anything else. This is a strong conclusion. Aristotle is claiming that the existence of everything other than primary substances would be impossible were there no primary substances. From this it would follow that the world of uninstantiated universals in the absence of primary substances is a fiction.
This conclusion is evidently intended to show that universals (both those that are present in a primary substance, and those that are not) are ontologically dependent on particulars, that they cannot exist independently of particulars. The question becomes whether or not this conclusion also implies that particulars can exist independently of universals. If so, it would turn out that particulars are ontologically prior to all the other things. The traditional answer to this question is “yes”. Traditionally, the relationship of ontological dependence between particulars and universals is seen as asymmetrical:
particulars can exist without universals, but not vice versa, and hence they enjoy ontological priority over universals.
The notion of ontological priority is traditionally identified with what Aristotle calls priority “by nature and substance”. In Metaphysics Δ 11, Aristotle states: “Some things
then are called prior and posterior (protera kai hystera) ... by nature and substance, namely all things which can exist without (einai endechetai aneu) other things, whereas others cannot exist without them – a distinction which was used by Plato” (1019a1-4). There are at least three things worth noticing about this statement of priority. Firstly, ontological priority amounts to the capacity for independent existence, and is expressed in modal terms: A is ontologically prior to B if A can exist without B while B cannot exist without A. The conclusion of the above passage is presented in similar modal terms – universals cannot exist without particulars.39 Secondly, ontological priority implies that the relation of ontological dependence is asymmetrical: A is ontologically prior to B just in case A can exist without, independently of, B but B cannot exist without A, i.e., the dependence is only one way.40 Thirdly, this notion of priority was, as Aristotle says, used by Plato. It is not overly surprising to find Aristotle endorsing what he takes to be a Platonic criterion for what is prior by nature and substance, given that Aristotle often uses the ideas of his predecessors for his own purposes. On the traditional interpretation,
39 Aristotle discusses a similar form of priority also in chapter twelve of the Categories: “What does not reciprocate as to implication of being [is called prior]” (14a30). Cleary (1988) argues that the priority “by nature and substance” and the priority as to the implication of being come to much the same thing – both “use the test of non-reciprocity on two related things in order to determine which of them is prior by nature” (p. 45).
40 Wedin (2005) claims that “virtually all commentators assume that the Categories brand of ontological dependence is asymmetric” (p. 81). Corkum (2008) summarizes the prevalent understanding of the Categories in the following way: “Aristotle holds that individual substances are ontologically independent from non-substances and universal substances but that non-substances and universal substances are ontologically dependent on substances. There is then an asymmetry between individual substances and other kinds of being with respect to ontological dependence. Under what could plausibly be called the standard interpretation, the ontological independence ascribed to individual substances and denied of non- substances and universal substances is a capacity for independent existence” (p. 65).
Aristotle uses this Platonic criterion of priority in a fairly radical manner, viz., he uses it to overturn the Platonic position.
Nonetheless, it is important to notice that the above passage establishes only the ontological dependence of universals and accidents on particulars. It does not establish the ontological independence of particulars. In fact, nothing in the above passage excludes the possibility that the relation between particulars and universals is one of mutual ontological dependence. Why, then, does the traditional interpretation maintain that Aristotle is committed to the ontological priority of particulars?
I believe that the traditional interpretation relies on two assumptions. The first assumption is that the relation of predication expresses ontological dependence – what is said of a subject is dependent on this subject for its being. The second and more important assumption is that the relationship between a subject of a predication and its predicate is irreducibly asymmetrical (i.e., predicates are predicated of subjects but not
vice versa).41 Given these assumptions, it is clearly tempting to conclude that the relationship of ontological dependence between particulars and universals must likewise be asymmetrical. A further motivation behind the traditional interpretation might be Aristotle’s terminology. After all, Aristotle calls primary substances “primary” which might suggest that he attributes to them ontological primacy over universals.42 Finally, some43 contend that the conclusion of the above passage – “if the primary substances did
not exist it would be impossible for any of the other things to exist” – would simply be pointless unless it is implied that the dependence is asymmetrical. However, there are
41 This assumption has persisted successfully in the history of philosophy, and has been challenged seriously only recently. One of the first authors who vigorously denies it is Ramsey (1925); he argues that there is no fundamental antithesis between subjects and predicates, and hence no irreducible asymmetry. 42 See, e.g., Corkum (2008, 70).
reasons to doubt that Aristotle would be committed to this implication. The critical consideration here is the reason Aristotle gives for calling species and genera “substances”, which leads us to his essentialism.