Thinking about Substance

The Development of Aristotle's Thought

Outline of Categories 1-5:

Chapter 1. Names
Chapter 2. The division of reality
Chapter 3. Predicates
Chapter 4. The ten categories
Chapter 5. Substance
In the Metaphysics, Aristotle tries to correct what he sees as mistakes in the ontology and theory of substance and existence he presented in the Categories.

The Ontology in the Categories


In general, it is unknown when Aristotle wrote particular works. The Categories, though, is an exception. It is thought to be one of Aristotle's earliest works.
The Categories is an early work written not long after Aristotle left the Academy.


"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. 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 5.2a).
The discussion is about terms. Terms are parts of language. To identify the parts of reality terms signify, "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 5.2a).

Aristotle uses ὁ τὶς ἄνθρωπος ("this man") to refer to a particular man, this or that man, as opposed to ἄνθρωπος ("man"), the kind to which human beings belong.

"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 5.2b).
Aristotle divides reality (τὰ ὄντα "the beings") along two dimensions:

• particular and general
• object and property

Plato had emphasized the ontological division between particular and general 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 objects and properties. 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.

Aristotle makes particular objects the "primary substances" (πρῶται οὐσίαι). They are the foundation in that everything else depends on these objects for its existence.

There are lots of questions to ask about Aristotle's ontology, but the first thing to notice is that it is much more striking than it may initially appear. Consider the sentences,

• 'Socrates is a man'
• 'Socrates is pale'

Aristotle understands the term 'Socrates' to signify a particular object, Socrates. He understands 'man' to signify an object too, and this can be surprising. One might think that although individual human beings exist, man does not exist. Further, if man does exist, one might think it is a property. According to Aristotle, however, the term 'man' signifies a general object, man.

Aristotle's understanding of the second sentence can be surprising too. One might think term 'pale' signifies a general property, but this is not how Aristotle understands the sentence. He takes the term to signify a particular property and takes the sentence the particular if the particular object the term 'Socrates' signifies contains the particular property the term 'pale' signifies.

The Oneness and Unity of Individuals


"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 5.3b).
Another surprising thing about Aristotle's ontology in the Categories is its explanation of the individuality of particular objects. Socrates, for example, is one thing, not a heap of things in close proximity to each other, and the philosophical problem is to explain this oneness.

Aristotle thinks that the particular objects he identifies as primary substances have the oneness and unity characteristic of individuals because they are the "atomic" parts of general objects. What Aristotle has in mind is not easy to see, but the idea is that the general object animal, for example, is divisible into more specific general objects, such as man. Man is not further divisible into general objects, but it is divisible into the many particular men. These men are indivisible (because the parts of human beings are not human beings) and hence they are the "atomic" parts of man. This indivisibility, Aristotle thinks, is the oneness that makes a particular man an individual.

Problems in the Ontology

Aristotle does not explain why he returns to the question of substance in the Metaphysics, but it seems that he came to think that "this or that man" cannot be a primary substance.

The objects salient in ordinary experience, such as "this or that man," do seem to have a certain primacy. They seem more fundamental than their features, but this does not seem true of the primary substances in the Categories. Given that the particular objects are the atomic parts of general objects, the primary substances seem to depend for their existence on the secondary substances. In addition, since the "this or that man" is a particular object with a set of particular properties, the primary substances also seem to depend for their existence on the properties.

Change also poses a problem for the ontology.

For example, we ordinarily think that it is possible for Socrates to become pale. Further, in this we think that Socrates would at one moment is not be pale and would at a later moment be pale. It is unclear that such a change can be accommodated in the ontology he sets out in the Categories because it is unclear what would persist.

"[W]hat is most characteristic of substance appears to be this: that, although it remains, notwithstanding, numerically one and the same, it is capable of being the recipient of contrary qualifications. Of things that are other than substance we could hardly adduce an example possessed of this characteristic. For instance, a particular colour, numerically one and the same, can in no wise be both black and white, and an action, if one and the same, can in no wise be both good and bad. So of everything other than substance. But substance, remaining the same, yet admits of such contrary qualities. One and the same individual at one time is white, warm or good, at another time black, cold or bad. This is not so with anything else" (Categories 5.4a).

We also ordinarily think that Socrates is not eternal, that he came into and subsequently went out of existence. This kind of change too poses a problem for the ontology.
This problem, it seems, perhaps among others, convinces Aristotle to think again about what things are substances and thus are things in terms of which the existence of all other things is to be understood. How Aristotle answers this question in the Metaphysics remains a matter of debate among historians, but it seems clear that he no longer thinks the primary substances are "this or that man" and "this or that horse," where these objects are understand as the concrete objects we are familiar with in experience, objects of a certain size, weight, color, and so on.

Further, although again this is a matter of debate, Aristotle no longer seems to think that general objects such as man and horse exist. It follows, then, if this is right, that he can no longer accept the explanation of the individuality of Socrates and the other particular objects because if there are no general objects, particular objects cannot be the atomic parts of general objects.

Primary Substances are Forms

In the Metaphysics, as we saw in the prior lecture, Aristotle thinks that substances are "separable and immutable." This suggests to him that forms are the primary substances, not the concrete objects (the "this or that man" and "this and that horse") he identifies in the Categories.

Further, since substances are "separable and immutable," and only divine beings meet these conditions without qualification, they are the substances without qualification and hence are the primary substances. In the Metaphysics, then, as in the Categories, the primary substances are particular objects. What changes is the primary objects Aristotle identifies.

Moreover, in the Metaphysics, Aristotle thinks that some objects meet the conditions for substance only with qualification and in this way are secondary substances. These objects, however, are not man, animal, and the other general objects he identifies as secondary substances in the Categories. They are the particular objects Aristotle understands as forms but as forms in matter.

We can begin to understand the relation between these two ways of being a substance if we consider the way Aristotle conceives of the human soul. We saw, in a prior lecture, that he understands the human soul to be the form of a living human being. If this form is a substance, as in fact Aristotle thinks, then it has the characteristics that mark this kind of being.

In the lecture in which we saw that Aristotle understands the soul to be a form, we also saw that he thinks it is "separable." As the organization of the materials that constitutes a living human being, the soul does not exist apart from the material it organizes and hence does not have an existence separate from the matter. The soul, however, is separate in a another way in that the account does mention flesh, bone, or any other particular material. In this way, the soul is "separable" but with qualification. Its existence is separate from matter in account.

We also saw that Aristotle thinks the soul is the starting-point for change but does not itself change, but it does not follow that the soul exists the same at every moment in time. The soul is not eternal. It exists for the time the human being is alive. Further, because some of the activities that constitute a human life are exercised at different times, the soul is different at different times. So, before the acquisition reason, when the human being is a child, the soul as the organization of the material is in a certain state. It is in a state that explains the way children naturally behave in various circumstances. Subsequently, after the acquisition of reason, when the human being has matured and become an adult, the soul as the organization of the material is in a different state. It is in a state that explains the way adults naturally behave in various circumstances. In this way, the soul is "immutable" but with qualification. It is immutable with respect to change.

It remains to know how Aristotle thinks the explanation of divine existence as a form includes, because theology as first philosophy is "universal," an explanation of human existence as a form in matter. The answer is difficult to see clearly, but it seems to be that existence as a form is existence as an actuality without potentiality and that to explain this existence, it is necessary to explain existence as an actuality with potentiality and this is the existence of a form in matter.

Actuality and Potentiality

At this point, then, to understand Aristotle's conception of substance a little more clearly, we need to see how he understands form and matter in terms actuality and potentiality.

This is an enormous undertaking, but it helps, again, to consider this issue in terms of Aristotle's conception of the soul. In Book II of On the Soul, once he turns to the question of what the soul is, Aristotle immediately starts talking about substances. The implication is that souls are substances, but before he makes this argument, notice that he explicates substances in terms of matter and form and explicates matter and form in terms of potentiality and actuality.

"The theories of the soul handed down by our predecessors have been sufficiently discussed; now let us start afresh, as it were, and try to determine what the soul is, and what definition of it will be most comprehensive. We describe one class of existing things as substance; and in this there is matter, which in itself is not an individual thing; shape or form, that according to which something is individual, and the compound of the two. Matter is potentiality, and form is actuality (ἔστι δ᾿ ἡ μὲν ὕλη δύναμις, τὸ δ᾿ εἶδος ἐντελέχεια)..." (On the Soul II.1.412a).

Given this very brief discussion of the ontology in terms of which he will say what the soul is, Aristotle goes onto argue that the soul is the "first actuality" of a certain kind of body.

"Substances most of all are thought to be bodies, especially natural bodies, for they are the starting-points for other bodies. Of the natural bodies, some have life and some do not. Life we say is self-nutrition and growth and decay. Thus every natural body having life is a substance as a composite. But since it is a body of a definite kind, viz., having life, the body cannot be soul, for the body is not something predicated of a subject, but rather is itself to be regarded as a subject, i.e., as matter. So the soul must be substance as the form of a natural body, which potentially has life. And substance is actuality. The soul, then, is the actuality of a body. But actuality is of two kinds, corresponding to knowledge and contemplation. The soul is an actuality like knowledge. Sleeping and waking presuppose the existence of soul, and waking corresponds to contemplation, sleeping to knowledge since it comes first. That is why the soul is the first actuality (ἐντελέχεια ἡ πρώτη) of a natural body having life potentially in it" (On the Soul II.1.412a).

This provides the beginning of a glimpse into the way Aristotle understands how the sensible substances physics studies have an existence that is a qualification of the existence that characterizes the divine substances theology studies. Since divine substances are forms, it falls to theology to explain what existence as a form is. The explanation will be that forms exist as actualities that do not involve any potentialities. In this way, because the divine substances exist as forms, their existence is existence as pure actuality. Further, because the explanation of existence as a pure actuality will include an explanation of existence as an actuality involving potentialities, theology is also first philosophy. Existence as an actuality involving potentialities is the existence as a form in matter that characterizes the sensible objects that physics studies.




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).

"In the Metaphysics, Aristotle denies that there are genera or species, that is, he denies that universals really exist (cf. [Metaphysics] Z 13). Yet, if there are no genera and species, individuals no longer can be taken to be the ultimate, indivisible parts of genera [as he claimed in the Categories]" (Michael Frede, "Individuals in Aristotle," 63. Essays in Ancient Philosophy, Michael Frede (University of Minnesota Press, 1987), 49-71).

"[In the Metaphysics, Aristotle] sees that it cannot be the ordinary objects of experience that underlie the properties, if there are to be properties in addition to the objects; for the ordinary objects of experience are the objects together with their properties—an ordinary object has a certain size, weight, temperature, color, and other attributes of this kind. So, if we ask what is it that underlies all these properties and makes them the properties of a single object, we cannot answer: just the object. For the object, as ordinarily understood, already is the object together with all its qualities; what we, however, are looking for is that which underlies these qualities. Thus we can see why Aristotle now considers answers like 'the form' or 'the matter' when considering the question, what actually is the underlying substance" (Michael Frede, "Individuals in Aristotle," 64. 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 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. 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' [οὐσίαι] 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).

"[I]t would seem that the forms of natural substances somehow are an inferior kind of forms in yet another way. For they are separate only qualifiedly, namely, in account; and they are unchanging, but only qualifiedly. For though they do not come into being or pass away, they, unlike separate forms, do not exist eternally, but go in and out of existence instantaneously. And though they do not suffer change, they really are different at different times, as one can see in the case of human souls" (Michael Frede, "The Unity of General and Special Metaphysics: Aristotle's Conception of Metaphysics," 91. Essays in Ancient Philosophy, Michael Frede (University of Minnesota Press, 1987), 81-95).

"[T]he forms at least of ensouled things are not subject to change, at any rate, not in the sense in which Aristotle's natural philosophy approaches changeable objects, though they are principles of change and can have a very rich history, simply because the characteristic capacities of a living thing—which are what constitutes the soul, i.e., the form—can at various times be exercised or not exercised. If one sees something, it is not strictly speaking the soul which is undergoing some change but the living organism; nevertheless,the soul is a different soul, if one sees or has seen something" (Michael Frede, "Individuals in Aristotle," 69. Essays in Ancient Philosophy, Michael Frede (University of Minnesota Press, 1987), 49-71).

"A human soul, for instance, ... is in different states at different times, depending on whether the potentialities it is constituted by are actualized or exercised or not" (Michael Frede, "Introduction," 44. Aristotle's Metaphysics Lambda: Symposium Aristotelicum, Michael Frede & David Charles (Oxford University Press, 2000), 1-52).




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