Substance and Priority in Aristotle's Metaphysics

The notion of ontological priority is all the rage these days, and many point to Aristotle as the source  of the notion as it is used today.  However, even a brief look at Aristotle's Metaphysics reveals discussion of a wide variety of notions of priority relations among entities. Therefore, in an effort to get clearer on Aristotle's notion of ontological priority, I will here engage in a preliminary exploration of Aristotle’s senses of priority, and then point out ways in which he thought that an entity can be prior to and posterior to another. 

Before I begin, however, I must briefly discuss the entities that Aristotle had in mind that could stand in the aforementioned relations of priority.  These entities are matter, form (or essence), and substance.  Before we consider these, however, let me note that it will be unavoidable that I use the word ‘substance’ before I explicitly discuss it.  But I believe we have a rough and ready conception of substance that is sufficient for us to make due until then.  With that said, let’s now consider matter. 
Aristotle’s use of ‘matter’ has at least three main senses: (i) Prime matter: that “feature” of things that has no properties in itself, and which persists through all change.  “…the ultimate substratum is of itself neither a particular thing nor of a particular quantity nor otherwise positively characterized; nor yet negatively, for negations also will only belong to it by accident.” (Z3, 1029a23-25)  It can also mean (ii) the kinds of stuff of which ordinary things are composed.  This seems to be the implication of Z3, 1029a4.  In that context, Aristotle is discussing the ways in which ‘matter’ is used. In using as an example a bronze statue, he says, “By matter I mean, for instance, the bronze…” So it appears that, for Aristotle, such stuffs as bronze, wood, and water are examples of matter in this sense. Aristotle implies that matter isn’t a ‘this’, nor is it “separable” (Z3, 1029a28).  In saying that matter isn’t a ‘this’, Aristotle apparently means that matter isn’t a particular entity, capable of being referred to demonstratively.[1]   So, for example, wood, as a general kind of stuff, isn’t something one can point to.  Rather, one can only demonstratively refer to particular objects. What he means when he says that matter is not “separable” is a matter of considerable controversy, but apparently he means that matter can’t exist independently, but rather it must have some particular, determinate shape or form.  This seems to follow from its not being a ‘this’.  For if it can’t be referred to demonstratively as a determinate thing, then it is hard to see how it could exist at all on its own.  That is, it is hard to imagine an existent, yet indeterminate object (some quantum physicists notwithstanding).  (iii) Particular chunks of the matter described in (ii) are also counted as matter.  For example, the marble of a particular marble statue is an instance of matter in this sense.  Of course, Aristotle takes the bodies of organisms to count as matter as well: “It is clear also that the soul is the primary substance and the body is matter…” (Z11, 1037a5-6). 

Three terms must be defined before we go on, namely, ‘formula’, ‘essence’, and ‘definition’.  An essence is the feature of an entity that makes it the kind of thing that it is.  It is the characteristic, or set of characteristics that make a particular substance the thing it is.  “The essence of each thing is what it is said to be in virtue of itself.  For being you is not being musical; for you are not musical in virtue of yourself.  What, then, you are in virtue of yourself is your essence.” (Z4, 1029b13-15)

A formula is a meaningful string of words.  For example, a sentence and a book-length treatise are both formulae.[2]  

Finally, a definition is a formula that denotes the essence of a particular substance.  “…the essence is substance, and the definition is a formula of the essence.” (H1, 1042a16-17). 

Aristotle changes his notion of definition in the process of working out his theory of substance in his Metaphysics.  For in Book Zeta (especially chapter 12), he seems to suppose that the definition of a thing is given by citing the genus to which it belongs and the last differentia that individuates it.  So, for example, on the early view, a definition of say ‘man’, would run something like this: “a man is a two-footed animal,”[3] where “animal” denotes the genus and “two-footed” denotes the differentia.  This definition is surely unsatisfactory, but the idea seems clear enough: to give a definition is to cite the main genus and that which differentiates it from other things in that genus.  

According to his later view of definition, things are completely different.  For on that view, one doesn’t list things like the genus and differentia, but rather the type of matter of a thing and its form.  This latter type of definition is implied in H2: “…If we had to define a threshold, we should say ‘wood or stone in such-and-such a position’…and if we define ice we say ‘water frozen or solidified in such-and-such a way’…” (H2, 1043a7-10).  So on this type of definition, a thing is defined according to the following schema: “an F is such-and-such matter having such-and-such a form.”

‘Form’ has at least as many senses for Aristotle as does ‘matter’.  In one sense of ‘form’, it means the component of a particular substance that makes it the kind of thing it is. That is, it is the essence of a substance.  We will discuss Aristotle’s notion(s) of substance shortly.  But for now, let it be noted that often, Aristotle simply equates substance with essence: “Clearly, then, each primary and self-subsistent thing is one and the same as its essence.” (Z6, 1032a4-5) 

In another sense, ‘form’ is the universal version of the particular instances of forms mentioned above. For again, Aristotle equates the essence of a thing with its form. “By form I mean the essence of each thing and its primary substance.” (Z7, 1032b1-2)  But we have seen that essences have definitions.  And definitions are of universals.  “…For definition is of the universal and of the form.” (Z11, 1036a28-29)  Thus, forms are universals. 

In yet another sense of ‘form’, Aristotle means the soul of a living being. “…the soul of animals (for this is the substance of living beings) is their substance according to the formula, i.e. the form and the essence of the body of a certain kind…” (Z10, 1035b14-17) Souls are a very special kind of form for Aristotle.  For as we will see shortly, souls seem to have an especially deep unity to them.  Indeed, Aristotle sometimes seems to think that only souls are genuine forms.[4]  In any case, it is clear that although all souls are forms, but of course the converse does not hold.  For example, the form of a house is clearly not a soul.  There are many other fascinating features of souls as Aristotle conceives them, but we will not discuss these here. 

Finally, we must try to shed some light on what Aristotle means by ‘substance’. In Z17, Aristotle argues that the forms of particular perceptible substances are the cause of their unity and being.[5] At the end of the chapter, he illustrates this point with some examples, one being the unity of flesh and the other, the unity of a syllable.  In both cases, we seem to have certain elements in a certain configuration: B and A, plus their being ordered in the sequence BA; fire and earth configured in such a way as to be flesh.  Now Aristotle points out that the syllable and the flesh are not merely their elements: letters, and fire and earth.  “For on dissolution the flesh and the syllable no longer exist, but the letters exist, and so do the fire and the earth.” (Z17, 1041b13-16) Therefore, he concludes that there is “something else” in a unified entity that exists besides the elements.  “It would seem, then, that this something else does exist, and that it is not an element, and it is the cause of this thing here being flesh and that thing there being a syllable. And similarly in other cases. And this is the substance of each thing, because it is the primary cause of its being.” (1041b25-27.  Emphasis mine) Aristotle goes on to say that “not all objects are substances, but only those that are formed naturally and in accordance with their nature…” (1040b28) From this it is clear that for Aristotle, the form of a thing is its substance.  However, in H2, he allows that particular compounds of matter and form be called ‘substances’.[6]  Henceforth, let’s follow Aristotle in considering such compounds as substances (at least in a derivative sense, in that they have forms), but call such substances ‘compounds’.

It is important to notice that in Aristotle’s examples of the syllable and the flesh, the form “within” them unifies them and makes them each one thing.  If we flesh out the “flesh” example, and take it to be the body of a living thing, we see a deeper unity.  For unlike the “syllable” example, the parts of a body cease to exist qua body parts when removed from the body.  And all of the parts are what they are in virtue of the existence of the whole. This seems to be Aristotle’s point in Z10, 1035b22-25, in his discussion of priority relations between the parts of a thing and the whole. “So the bodily parts are prior to the combined whole in one way...for they cannot exist separated from it. (It is not a finger in any and every state that it is the finger of an animal; a dead finger is a finger only in name)”.

In H6, Aristotle gives his final account of the unity of compound substances. Here, he incorporates his new account of definitions to explain such unity.  Recall that with the new account, the definition of substance is given by citing the kind of stuff (i.e., the matter) it has, plus its configuration (i.e., its form).  Therefore, there is now no set of predicates in the definition that are on a par, for then there would be a need for an extra thing to combine/unify them.  Instead, on the new account, form and matter are radically different things, so this need is eliminated.  Furthermore, the matter and the form existentially depend on each other.  Matter cannot exist except as configured in a certain way. Form cannot exist unless it is the form of something.  In these ways, then, a compound perceptible substance is a unity.[7] With these key concepts and terms discussed, we are now ready to discuss the ways in which matter, form, and compounds are prior to and/or posterior to one another.

Aristotle argues that form is prior to matter in the order of knowledge. That is, the form is what we know when we know what a thing is.  For as we have seen, he equates the form of a thing with its essence. And he argues that the essence of a thing is what we know when we know what a thing is.  “For there is knowledge of a thing only when we know its essence.” (Z6, 1031b6-7)  Thus, the form of a thing is what we know of when we have knowledge of a thing.  So, for example, when I learn what it is to be a cat, I don’t know this by knowing that it has such-and-such matter.  Rather, I know its form, or essence, and this is expressible in a statement, or formula.  If one were asked what a particular thing was, while pointing at a cat, one would not tell them that, say, it was white.  At least, if one did, one would not convey any information about the cat qua cat.  If that were all that one was given to go on, it would not be sufficient to be able to tell the difference between a cat and a dog, or any other white thing (supposing that it was white).  So, to be able to pick out a cat by way of a formula, one would have to cite something unique to all cats, and something that a cat must possess to qualify as a cat.  And to do this, one must make reference to its essence, or form.

Aristotle holds that substance is prior in formula.  That is, when we describe any given thing, from any category, we make reference to substance, or essence.  Aristotle describes priority in formula in this way: “And in formula also this is primary; for in the formula of each term the formula of its substance must also be present.” (Z1, 1028a35-37)  As we have seen, a formula is a meaningful string of words, such as a sentence.  In this passage, the relevant formulas seem to refer to the definitions of terms of things.  So if we remove the specific application to substance in his account of priority in formula, Aristotle seems to be saying that if something, a, is prior in formula, then for every term T that denotes an entity, E, the definition of T (which is also a definition of the entity) will contain or make reference to the formula of a.  So, for example, suppose that one were giving the formula of the term ‘red’.  In spelling out that definition, one will have to make a general reference to red things, i.e., to red substances.  And if the definition is to be absolutely complete, the definition of ‘substance’ must be mentioned.[8]

Aristotle also argues that actuality is prior in formula to potentiality in Theta 8.  “For that which is in the primary sense potential is potential because it is possible for it to become actual, e.g., I mean by ‘capable of building’ that which can build, and ‘capable of seeing’ that which can see…so that the formula and the knowledge of the one must precede the knowledge of the other.” (Theta 8, 1049b12-18)  It appears that Aristotle’s examples are meant to illustrate the fact that one must have knowledge of the actual thing in order to understand the potential thing.  That is, one must know what it is to build something before one can know what it is to be capable of building.  Similarly, one must know what it is to actually see before one can know what it is to have the capacity to see.  And we have seen that Aristotle takes knowledge to be of definitions, and definitions are of forms. Thus, since form is in the category of actuality, and matter is in the category of potentiality, we may argue that form is prior in formula to matter.

In a relatively unimportant sense, both form and matter are prior in time[9] to the compound.  That is, the form and the matter of a thing exist temporally prior to the compound. Of course, as we have seen, pure matter cannot exist without some form or other, since it’s not separable or a ‘this’.  Similarly, apart from the prime mover, it is clear that forms of things don’t exist apart from particular matter.  So we must take Aristotle to mean that the matter of a new compound existed antecedently in another compound, and the form had other instances in antecedently existing compounds.  This is true for both artifactual and living compounds. This is stated in Z9, where Aristotle is arguing that in the generation of a thing, something must exist before such generation.   In artifactual cases, the form of the artifact exists beforehand in the mind or soul of the person. So, for example, a person, through skill, makes the form reside in a particular chunk of matter, and the result is a particular substance, conceived as a composite of matter and form. “…All makings proceed either from art or from a capacity or from some thought…from art proceed the things of which the form is in the soul.” (Z7, 1032a26-31)

In the case of living things (excluding divine beings), the form (which is a soul in the case of organisms) exists beforehand in the male parent.  Through copulation, the form is passed, by way of the male issue, to the ovum, and it enters the ovum resulting in a particular living being.  “Things which are formed by nature are in a similar situation.  In the one case they are produced from seed, and this resembles the products of skill, for the seed has the form potentially.” (Z9, 1034a33-36)  In all cases, then, the form of a particular substance exists temporally prior to the compound.  And, of course, the matter is also clearly present beforehand in all cases: “Obviously then some part of the result will pre-exist of necessity; for the matter is a part; for this is present in the process and it is this that becomes something.” (Z9, 1032b30-33) 

In Theta 8, Aristotle seems to have things to say that are related to the last point. For there he says that actuality is prior in time, in the sense that,  “…the actual member of the species is prior to the potential member of the same species, though the individual is potential before it is actual.  I mean that the matter and the seed and that which is capable of seeing, which are potentially a man and corn and seeing, but not yet actually so, are prior in time to this particular man who now exists actually… ” (1049b17-21) It seems clear that here Aristotle is saying that only actually existing things produce actually existing things. Actually, he puts it more clearly and precisely: “For from the potential the actual is always produced by an actual thing, e.g., man by man, musician by musician…” (Th8, 1049b23-24) So matter, or mere potentiality, cannot make itself actual.  Only that which is actual can make a potential thing actual.  In this sense, then, actuality is prior to potentiality in time. In the passage we have been discussing, actually existing things are all examples of concrete, particular substances.  So it seems safe to conclude that substances are prior in time to matter, a merely potential thing.

However, in a more important sense, a particular compound substance is prior in separate existence to matter and to form.  That is, the concrete, particular substance, alone of all non-divine entities, is capable of existing on its own.  It doesn’t, nor can it be, predicated of another entity.   Aristotle misleadingly labels this type of priority, “priority in time” in Z1, 1028a32-33.  He implies the definition at 1028a34: “For of the other categories none can exist independently, but only substance.”  By contrast, a quality, such as redness, cannot exist without being predicated of another object.[10]  Aristotle declares perceptible compounds to be separable in this sense in H1. “What underlies is substance, and in one way this is matter…though in another way it is the shape…and in a third way it is what is compounded from these (and this alone can come to be and cease to be, and is separable without qualification…” (1042a26-31, italics mine)

On the other hand, the material parts of the compound are posterior to the compound as a whole.  That is, they cannot exist separately from the whole.  For the parts are what they are in virtue of their being members of the whole.  This is especially evident with living things.  As Aristotle argues, a hand is not a hand when severed from the body.  For, as we have seen, a hand is defined partly in terms of its function.  And this function is lost when removed from the body. Also, one cannot properly describe a hand without making reference to the living thing to which it is a part.  In these ways then, Aristotle argues, the parts of a compound substance are posterior to the wholes to which they belong.

Finally, he argues that the form is prior in substance.  In Th8, 1050a5-1050b5, Aristotle discusses this kind of priority, and two ways in which a thing may have it.  First, he says that things that actually have a particular form exist before those that do not yet “have” it, but are developing toward the point of having it fully instantiated within them. “…the things that are posterior to becoming are prior in form and in substance, e.g., the man is prior to the boy and human being to seed; for the one already has the form, the other does not.” (Th8, 1050a5-7)  This seems similar to Aristotle’s notion of priority in time mentioned earlier.  But secondly, form is prior in substance in that the potential thing (or, thing with potential?) exists for the sake of achieving a specific goal or end. The matter, or potential, of the thing exists for the sake of the active functioning of the particular substance.  “that for the sake of which a thing is, is its principle, and the becoming is for the sake of the end; and the actuality is the end, and it is for the sake of this that the potentiality is acquired.” (Th8, 1050a7-9) In these ways, then, matter, form, and compounds stand in relations of priority and of “posteriority” to one another.

It’s time to take an inventory and see what bearing it may have on answering our original query: which comes first, the matter of a thing, its essence, or its substance?  It depends on what the question means.  If it is a question of what ultimately produced what first, in the order of time, then it appears that the answer is that none fits that bill.  For according to Aristotle, the universe is eternal, and there have always been just the prime mover (who is pure form[11]), the unmoved movers, the celestial bodies (composed of imperishable matter and form), and terrestrial compounds (composed of perishable matter and form).  And on his view, the prime mover isn’t like the God of the monotheistic religions, who created the world out of nothing a finite amount of time ago. So, say, God doesn’t make the forms, for they cannot be created.[12]  And since the world is eternal, matter is uncreated and eternal: it had no ultimate temporal beginning. So it appears that, as far as compounds go, it has been an endless progression of one or more compound creating another compound by putting a pre-existent form into a pre-existent compound.

But if the question means, what existentially depends on what, or what is existentially independent, then the answer is a little more interesting.  For in light of his ideas concerning (a) the unity of compounds, (b) the priority of compounds in separate existence, and (c) the priority of the whole over the parts, we may say that the matter and the form mutually depend upon each other for their existence.  For according to (a), the matter needs to be informed to be determinate and an existent, and the form needs to be in matter to be an existent.  According to (b), matter and form can exist only if they are compounded together.  And according to (c), the parts wouldn’t exist qua those parts without the whole existing, which presupposes both the matter and the form existing together.  So in this case, we must answer that both the matter and the form “came first”.  However, for Aristotle, the prime mover is pure form, and so here we have at least one form that doesn’t depend on matter to exist.  Perhaps in this one case, then, we may say that form came first.

This last point seems to raise a serious problem for Aristotle’s rejection of Plato’s self-subsisting Forms.  For if one form can exist without being instanced in matter, then why can’t they all?  What principled grounds could be offered for saying that while one particular form can exist independently, none of the others can?  For my part, I can’t think of any, and so it appears to me that Aristotle should conclude that form “came first” in this sense.

In summary, then, we have discussed Aristotle’s notions of form, matter, and substance, as well as related notions.  Furthermore, we have discussed the various ways in which these things are said to be prior and posterior to one another according to Aristotle. 


Aristotle.  A New Aristotle Reader. Ed. J.L. Ackrill. Princeton: Princeton University Press, 1987.

---, Metaphysics, Books Z and H.  Translated with a Commentary by David Bostock.  Clarendon Aristotle Series. Oxford: Clarendon Press, 1994.

Barnes, Jonathan, ed. The Cambridge Companion to Aristotle.  Cambridge: Cambridge UP, 1995.

Cohen, Marc.  “An Outline of Metaphysics Z.” <>. 11/20/01.

---, “Aristotle’s Metaphysics.” Stanford Encyclopedia of Philosophy. Ed. Edward Zalta. . 11/20/01.


[1] This interpretation of Aristotle’s notion of a ‘this’ is the view of Jonathan Barnes.  See his essay, “Metaphysics”, in J. Barnes, ed.  The Cambridge Companion to Aristotle (Cambridge: Cambridge UP: 1995), p. 91.
[2] This sense of ‘formula’ seems to be implied at Z4, 1030a6-9. “But we have a definition not where we have a word and a formula identical in meaning (for in that case all formulae would be definitions; for there will be some name for any formula whatsoever, so that even the Iliad would be a definition)…” 
[3] This example is taken from Bostock, David. Aristotle’s Metaphysics: Books Z and H, tr. and comm. David Bostock, Clarendon Aristotle Series (Oxford: Clarendon Press, 1994), pp. 178-80.
[4] For example, H6, 1043b21-23: “Perhaps neither these things themselves, nor any of the other things which are not formed by nature, are substances at all, for one might say that the nature in natural objects is the only substance to be found in destructible things.”  As we will see, Aristotle often equates form with substance.
[5] At Z17, 1041b7-9, Aristotle identifies the form of a thing with its substance. “Therefore, what we seek is the cause, i.e., the form, by reason of which matter is some definite thing; and this is the substance of the thing.”
[6] “… some who define a house say that it is stones, bricks, and timbers, and so give what is potentially a house, i.e., the matter; some say that it is a receptacle to shelter people and property…and they give the actuality; and some combine both, giving the third substance compounded from these.” (1043a14-19) 
[7] The discussion of this paragraph is indebted to that of Bostock, op. cit., pp. 287-290.  Indeed, it is a paraphrase of his discussion there!
[8] My discussion here is based on that in Bostock, op. cit., pp. 60-62.
[9] Bostock points out that Aristotle uses ‘prior in time’ in two senses: (i) capable of existing separately from other things, and (ii) existing earlier in time. (see the discussion in Bostock, Aristotle’s Metaphysics: Books Z and H, p. 63)  In this paper, I will try to avoid unnecessary confusion in this regard by using ‘prior in time’ solely as in sense (ii), and use the locution ‘prior in separate existence’ for sense (i).
[10] “…one might raise the question whether ‘to walk’ or ‘to be healthy’ and ‘to sit’ signify in each case something that is, and similarly in any other case of this sort; for none of them is either self-subsistent or capable of being separated from substance…” (Z1, 1028a20-24)

[11] Metaphysics, Book XII, Ch. 6, 107119-22.
[12] “Obviously, then the form also…is not produced, nor does production relate to it, - i.e., the essence is not produced…” (Z8, 1033b5-6)