The Ontology in the Categories

The Categories is an early work, presumably one Aristotle wrote close to the time when he was a student in Plato's Academy. (In general, it is unknown when individual works in the Aristotelian corpus were written. The Categories is an exception. It is thought to be one of Aristotle's earliest works.)

In the Categories, Aristotle discusses terms. Terms are parts of language. In his discussion, Aristotle discusses the parts of reality to which terms correspond. In this way, the Categories contains a discussion of ontology.

In the Categories, Aristotle divides reality along two dimensions:

• object versus property
• particular versus general

Plato had emphasized the ontological division between general and particular things. Aristotle thinks that there is an equally important division that Plato overlooked. In addition to the division between particular and general, Aristotle thinks that in reality there is a division between object and property. Thus, according to Aristotle, in reality there are four kinds of things: (i) particular objects, (ii) particular properties, (iii) general objects, and (iv) general properties.

Whereas Plato included the forms among the reality of things, Aristotle thinks that the primary substances are particular objects. As primary substances, particular objects are the foundation of existence. According to Aristotle, everything else exists because the primary substances exist.

Aristotle's ontology in the Categories is more radical than it may initially appear. Consider the sentence,

'Socrates is a man.'

Aristotle understands the term 'Socrates' in this sentence introduces a particular object, Socrates. He understands the term 'man' to introduce an object too. This can be surprising in two ways. First of all, one might think that man is not an object and something that exists at all. Further, given that one did think man is something that exists, one might think that it is a property. According to Aristotle, however, the term 'man' does not introduce a property. It introduces a general object.

Some terms do introduce properties, according to Aristotle. Consider the sentence,

'Socrates is pale.'

Aristotle understands the terms in this sentence ('Socrates' and 'pale') introduce a particular object and a particular property respectively. If the sentence is true, then reality is a certain way. According to Aristotle's ontology, reality is such that the particular object 'Socrates' contains the particular property that the term 'pale' signifies.

"A substance (οὐσία)--that which is called a substance most strictly, primarily, and most of all--is that which is neither said of a subject nor in a subject, e.g. this or that man (ὁ τὶς ἄνθρωπος) or this or that horse. The species in which the things primarily (πρώτως) called substances are, are called secondary (δεύτεραι) substances, as also are the genera of these species. For example, this or that man belongs in a species, man, and animal is a genus of the species; so these--both man and animal--are called secondary substances" (Categories V.2a). "All the other things are either said of the primary substances (πρώτων οὐσιῶν) 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" (Categories V.2a).

(Aristotle uses ὁ τὶς ἄνθρωπος ("this man") to refer to a particular man, the individual man (whoever he may be), this or that man, as opposed to ἄνθρωπος ("man" or "human being")).

"It is reasonable that, after the primary substances (πρώτας οὐσίας), their species and genera should be the only other things called secondary substances (δεύτεραι οὐσίαι). For only they, of things predicated, reveal the primary substance. For if one is to say of this man what he is, it will be in place to give the species or the genus (though more informative to give man than animal); but to give any of the other things would be out of place--for example, to say white or runs or anything like that" (Categories V.2b).

The Unity and Oneness of Individuals

Socrates is one thing, not a heap of things. The philosophical problem is to explain this oneness and unity.

In the Categories, the particular objects Aristotle identifies as primary substances have the unity, or oneness, characteristic of an individual because they are the "atomic" parts of general objects. The general object man is not divisible by any general object, but it is divisible by number. When the general object man is so divided, the many particular men are the result. These men are the indivisible and "atomic" parts of man. This indivisibility is what makes them be individuals. They have the unity that makes them be one object because they are indivisible.

"Every substance seems to signify a this (τόδε τι). As regards the primary substances, it is indisputably true that each of them signifies a certain this; for the thing revealed is individual (ἄτομον) and one in number. But as regards the secondary substances, though it appears from the form of the name--when one speaks of man or animal--that a secondary substance likewise signifies a certain this, this is not really true; rather, it signifies a certain qualification--for the subject is not, as the primary substance is, one, but man and animal are said of many things" (Categories V.3b).

In the Metaphysics, Aristotle seems to change his mind. He seems to think that general objects are no longer part of the ontology. This forces him to think again about the individuality of the objects he identifies as primary substances in the Categories. Since there are no general objects, individuals cannot be the atomic parts of general objects.

Just why Aristotle changes his mind from the Categories to the Metaphysics is hard to know, but he may have come to think that the "this or that man" (which he cites as an example of a primary substance in the Categories) cannot be a primary substance because there is no clear account of how "this or that man" is more basic than the general object man.

This problem, it seems, is why Aristotle returns in the Metaphysics to the question of what is substance most of all. How Aristotle answers this question remains a matter of intense scholarly debate, but he seems to argue that forms are substances and that the "this or that man" and "this or that horse" are not a primary substances because these objects are forms in matter.

Forms are Substances

In the Metaphysics, substances are "separable and immovable." Only divine objects meet these conditions without qualification, and hence only divine objects are substances without qualification. The forms in matter Aristotle identifies as the substances of natural bodies are separable and immovable with qualification.

"First philosophy treats of things which are both separable and immutable (ἡ δὲ πρώτη καὶ περὶ χωριστὰ καὶ ἀκίνητα)" (Metaphysics VI.1.1026a).

An example may help to make Aristotle's conception a little clearer.

The human soul is the form of a living human being. Since the human soul is a form, it is a substance. Since the human soul is a substance, it has the characteristics of this kind of being: it is "separable and immovable." At the same time, because the human soul is a form in matter, it is a form with qualification. The qualification is "in matter." Because the humnan soul is a form with qualification, it is a substance with qualification. The human soul is a substance. It is "separable and immovable," but it is "separable and immovable" with qualification.

(The first unmovable mover is unmovable without qualification. "[T]here is something which moves without being moved; something eternal which is both substance and actuality (ἔστι τι ὃ οὐ κινούμενον κινεῖ, ἀΐδιον καὶ οὐσία καὶ ἐνέργεια οὖσα) Now it moves in the following manner. The object of desire and the object of thought move without being moved" (Metaphysics XII.7.1072a).)

(Aristotle often seems to use μεταβολή ("change") and κίνησις ("motion") without distinction when he is talking about the kinds of change. "There is no such thing as motion (κίνησις) over and above the things. It is always with respect to substance or to quantity or to quality or to place (ἢ κατ᾿ οὐσίαν ἢ κατὰ ποσὸν ἢ κατὰ ποιὸν ἢ κατὰ τόπον) that what changes changes (μεταβάλλει) ... Hence there are as many types of motion or change as there are of being (ὥστε κινήσεως καὶ μεταβολῆς ἐστιν εἴδη τοσαῦτα ὅσα τοῦ ὄντος)" (Physics III.1.200b-201a).)

What are the qualifications that qualify "separable" and "immovable"?

Aristotle conceives of the human soul as the organization of various materials so that these material constitutes a living human being. As the organization of the materials, the soul is immune to certain kinds of changes. (This is one of the points Aristotle made against Plato. The soul is what accounts for certain ways in which a human being can change possible, but the does not itself does not change in these ways.) This immunity to certain kinds of change makes the human soul is "immovable." The soul, however, as Aristotle conceives of it, is not immune to every kind of change. No human soul exists eternally. It is fixed relative to specific behavior, but it is not fixed throughout all possible changes. In this way, the human soul is "immovable with qualification."

In addition to being "immovable with qualification," human soul is also "separable with qualification." As the organization of material, the human soul cannot exist apart from the material it organizes. (Aristotle made this point against Plato. He thought it was a mistake to think that the soul could exist independently of the body.) The soul, however, is separable from the material in a way. The account of what the soul is does mention flesh, bone, or any other particular material. Aristotle nowhere says what the soul is, but, as the form of the body, the soul is a certain organization. If to be human is to be a rational animal, then the soul is the organization of material so that a rational animal exists. In this way, the soul is "separable with qualification." It is separable in account.

Perseus Digital Library:
Aristotle, Metaphysics
Henry George Liddell, Robert Scott, A Greek-English Lexicon:
ἀκίνητος, akinētos, adjective, "immovable,"
ἄτομος, (ἀ + τέμνω), atomos, adjective, "uncut,"
μεταβολή, metabolē, noun, "change"
μεταβάλλω, metaballō, verb, "turn about, change, alter"
χωριστός, chōristos, adjective, "separable"

Arizona State University Library:
Loeb Classical Library:
Aristotle, Categories, Physics I-IV

"In the Metaphysics, Aristotle denies that there is anything general--at least, he denies that there are kinds, into which objects fall. Thus, he also abandons the notion of an individual which he had relied on in the Categories, since it presupposes that there are general things, that there are universals" (Michael Frede, "Individuals in Aristotle," 50. Essays in Ancient Philosophy, Michael Frede (University of Minnesota Press, 1987), 49-71).

"Although he retains the primary substances of the Categories, namely objects, these must now yield their status as primary substances to their substantial forms which now [in the Metaphysics] come to be called primary substances. The substantiality of concrete particulars is thus now only secondary. The idea of the Categories that substances are that which underlies everything else is retained, as we see from [Metaphysics] Z 1 and Z 3. However, the answer to the question what is it that underlies everything else has changed: now it is the substantial form" (Michael Frede, "The Title, Unity, and Authenticity of the Aristotelian Categories," 26. Essays in Ancient Philosophy, Michael Frede (University of Minnesota Press, 1987), 11-28).

"He continues to hold (cf., especially [Metaphysics Z3) as he had in the Categories, that objects can be called substances because they underlie everything else that exists in such a way that everything else owes its existence to them. Illness, for example, exists only insofar as there are objects that are ill. However, while Aristotle had proceeded in the Categories as if the idea, that substances underlie everything else, were quite unproblematic, in the Metaphysics, he begins to draw out some implications of this notion for what is actually to count as an object or substance" (Michael Frede, "Individuals in Aristotle," 64. Essays in Ancient Philosophy, Michael Frede (University of Minnesota Press, 1987), 49-71).

"[In the Metaphysics,] Aristotle thinks that substances are not as such composite [= forms in matter]. There are substances that are pure forms, as e.g., the unmoved mover. And it is clear from [Metaphysics] Z 3,1029 b 3ff. and Z 11, 1037 a 10ff. (cf. also Z 17, 1041 a 7ff.) that Aristotle thinks that the discussion of composite substances in Z H is only preliminary to the discussion of separate substances. We start by considering composite substances because they are better known to us, we are familiar with them, and they are generally agreed to be substances. But what is better known by nature are the pure forms. Aristotle's remarks suggest that we shall have a full understanding of what substances are only if we understand the way in which pure forms are substances. This, in turn, suggests that he thinks there is a primary use of 'substance' in which 'substance' applies to forms. Particularly clear cases of substance in this first use of 'substance' are pure forms or separate substances. It is for this reason that composite substances are substances only secondarily" (Michael Frede, "Substance in Aristotle's Metaphysics," 79. Essays in Ancient Philosophy, Michael Frede (University of Minnesota Press, 1987), 72-80).

"[S]ubstantial forms rather than concrete objects are the basic entities. Everything else that is depends on these substantial forms for its being and for its explanation. Hence substantial forms, being basic in this way, have a better claim to be called 'ousiai' or 'substances"' than anything else does. Some of them are such that they are realized in objects with properties. But this is not true of substantial forms as such. For there are immaterial forms. Properties, on the other hand, cannot exist without a form that constitutes an object. Moreover, though certain kinds of forms do need properties for their realization, they do not need the particular properties they have. The form of a human being needs a body of a weight within certain limits, but it does not need that particular weight. No form needs that particular weight to be realized. But this particular weight depends for its existence on some form as its subject. In fact, it looks as if Aristotle in the Metaphysics thought that the properties, or accidental forms, of objects depended for their existence on the very objects they are the accidental forms of, as if Socrates' color depended on Socrates for its existence. However this may be, on the new theory it is forms that exist in their own right, whereas properties merely constitute the way forms of a certain kind are realized at some point of time in their existence" (Michael Frede, "Substance in Aristotle's Metaphysics," 80. Essays in Ancient Philosophy, Michael Frede (University of Minnesota Press, 1987), 72-80).