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"Unity in Aristotle's metaphysics H6".


One recurring theme in the central books of Aristotle's Metaphysics is the unity of substance. This issue is discussed at length in both Z 12 and H 6, and in less detail in several other places (e.g., in Z 17, 1041b11-33 and H 3, 1043b4-14). These two chapters present the scholar with a number of problems: they contain no cross-references and they offer what are apparently differing solutions to the problem of unity. Each chapter also presents its own textual and philosophical problems. On H 6, which will be the focus of this paper, there is virtually no agreement among scholars on any of the major issues that arise. There is, for instance, no agreement on whether the chapter means to address the unity of forms or composites, nor about the nature of Aristotle's solution. But finding answers to these questions is crucial if we are to make sense of the central books of the Metaphysics and their relationship to the rest of the Metaphysics and the corpus. H 6 stands at the end of the two-book work of Z-H, and it addresses issues which have been in play throughout--in particular with the important but difficult issues of the matter-form relationship and the relationship between potentiality and actuality. (1) The latter issue is discused in more detail in Metaphysics [THETA], while the former is prominent in Aristotle's account of the relationship between body and soul in the De Anima.

A clear understanding of how these issues are dealt with in H 6 is therefore needed. While I do not claim to have provided a definitive account, I believe we can make significant progress on the chapter's main issues, particularly the nature of the chapter's aporia and of Aristotle's solution. (2) On the question of the chapter's main aporia two camps have emerged, with one taking Aristotle's primary explanandum to be the unity of composites, and the other the unity of forms. (3) Those who take the aporia to concern composites typically read the solution as requiring both matter and form, whereas those who take form to be paramount tend to downplay the role of one element or the other, usually matter. In contrast, my own view combines elements of both approaches. H 6, I argue, is concerned with both problems of unity, though the unity of form has a certain priority. On the issue of Aristotle's solution, most scholars take the object's form to be the sole, or at least the primary, explanation for its unity. Against this reading, I hold that Aristotle's solution relies equally upon form and matter. While I incorporate the insights of both sides, it seems to me that both get something wrong in that they fail to see the extremely close connection between composite and form, and, thus, between the two problems of unity. Although Aristotle is in one sense primarily concerned with forms, his discussion applies to composites as well.

I begin by developing a reading of the aporia in H 6 that focuses on the unity of (substantial) forms, though not at the expense of composites. But the bulk of my discussion will be concerned with Aristotle's solution, which I begin in [section] 3. Here I discuss and criticize Verity Harte's view that Aristotle solves the problem of the unity of form with the claim that forms are "immediately one". I argue instead that Aristotle identifies the problem of the unity of form with that of the unity of the composite such that both problems are to be solved by hylomorphism. Like individual composites, substantial forms are themselves matter-form composites, and it is in virtue of this that they are unified. But in order to understand this unity we must understand Aristotle's claim that matter is potentiality and form is actuality, and in [section] 4 I turn to these notions. I argue that Aristotle's solution is ultimately a deflationary one: once we understand the relationship between matter and form, potentiality and actuality, we need not seek a further cause of the unity of the object. This is because Aristotle takes the matter and form of substances to be reciprocal, correlative entities, each essentially related to its counterpart. [section] 5 highlights a complication of Aristotle's conception of matter and argues that in H 6 Aristotle understands the genus of a substantial form as intelligible matter, thus allowing intelligible objects like substantial forms to have a hylomorphic structure.

My interpretive starting point will be Verity Harte's "Metaphysics H.6: A Dialectic with Platonism", a paper which makes a number of important advances and bears careful discussion. Harte argues for two main claims: first, that the problem at issue in H 6 principally concerns the unity of forms; second, that Aristotle solves this problem in a passage (1045a36-b7) where he discusses objects with no matter. On Harte's view, Aristotle's answer to the problem of the unity of forms is to take substantial forms to be "immediately one" in an unanalyzable and unproblematic way. I have already noted that I reject this view of the nature of forms. I will, however, agree with Harte's reading of the chapter's main problem. And even the problems with Harte's reading will bear fruit by leading us towards the view that substantial forms are unified in virtue of their having a hylomorphic structure. The position I defend is in many respects similar to that of W.D. Ross, though it goes beyond Ross to offer a much more detailed defense of the reading as well as an analysis of important developments in the recent literature.


We begin with the aporia of H 6. Here is a brief sketch of why we should think it mainly concerns the unity of forms. The aporia is introduced with a question: "What then is it that makes man one; why is he one and not many, e.g. animal--biped ...?" (1045a14-15) Aristotle continues:

"Why are not those Ideas [sc. Biped and Animal] the ideal man [[TEXT NOT REPRODUCIBLE IN ASCII]], so that men [[TEXT NOT REPRODUCIBLE IN ASCII]] would exist by participation not in man, nor in one Idea, but in two, animal and biped? And in general man would be not one but more than one thing, animal and biped." (1045a17-21) (4)

I will discuss the passage in more detail below, but for now we should notice that (as Harte, Dialectic, pp. 284-5 has shown) the puzzles raised here are issued as challenges to certain Platonists. Aristotle's explicit reference to Platonic forms, along with his adoption of Plato's standard definition for man--biped animal--shows whom he is targeting. (5) And the fact that Aristotle is engaged in a dialectic with the Platonists provides prima facie support for the claim that H 6 is principally concerned with forms, because questions concerning forms were among the Platonists' principal metaphysical interests. This is not to say that H 6 has only dialectical import or that the problem of unity can only arise for the Platonists. Aristotle sets out the issue as being problematic for the Platonists in particular, but, as we shall see, issues central to his own ontology, such as the matter-form relationship, are involved in his solution.

Another reason to think H 6 is concerned chiefly with forms is that in a closely related chapter, Metaphysics Z 12, we also find "man" used to denote a form, along with strikingly similar language used to introduce the problem, though without raising the problem of composites:

"[W]herein consists the unity of that, the formula of which we call a definition, as for instance in the case of man, two-footed animal; for let this be the formula of man. Why, then, is this one, and not many, viz. animal and two-footed?" (1037b11-14)

Now, Z 12 functions as the conclusion to Aristotle's discussion of essence (i.e. form) as a candidate for substancehood. It is thus widely agreed that the discussion in Z 12 is concerned with the unity of substantial forms, and the parallels between it and H 6 suggest that H 6 is also concerned with forms.

Finally and most importantly, the details of Aristotle's argument show that forms are primarily at issue. In our H 6 passage, he identifies certain Platonist commitments and argues that they lead to the absurd conclusion that neither man nor men are unities (and thus not genuine substances). We can more clearly see the Platonists' mistake by noticing Aristotle's shift from "man" in the singular to "men" in the plural, where the former denotes a form and the latter individual composites. Aristotle's argument proceeds as follows. Since the Platonists take both terms in the definition of man [[TEXT NOT REPRODUCIBLE IN ASCII]] to denote forms, they in effect make one thing--the form man--into two--biped and animal--and thus make the form man disunified. Given Platonic doctrine that forms are ontologically independent of one another, they have no way to avoid this conclusion. (6) If that were not problematic enough, Aristotle then identifies a second problem arising from the first. Since, on the Platonist view, men [[TEXT NOT REPRODUCIBLE IN ASCII]] exist in virtue of their participation in the form man, men will participate (and participate essentially) in two forms, and thus individual men too will be more than one thing. So the Platonists' failure with respect to the unity of form leads them to a second failure for the unity of composites, thus putting the unity of both types of entity at risk.

On this analysis there are two closely connected problems at work in the passage, with the problem concerning forms being the source of the problem concerning composites. This suggests that those commentators who take H 6's principal explanandum to be the unity of form are correct. But given their close connection, it also suggests that Aristotle means to solve both problems of unity. For this and other reasons I do not entirely disagree with those who hold that H 6 is chiefly concerned with composites. Which problem of unity, then, does Aristotle mean H 6 to solve? The answer is both. As Harte puts it, the double failure for the Platonists suggests a double success for Aristotle. (7) But given that the problem of the unity of composites is a result of that concerning forms, we can expect Aristotle to concentrate on the unity of form. (8) The two problems are connected, I shall argue, in a deep way: they are ultimately the same problem, since forms are themselves composite entities.

This understanding of the problem allows us to incorporate the insights of different readings of the chapter's opening, including much of the evidence that the chapter is mainly concerned with composites. For example, it is true, as many commentators point out, that Aristotle draws out his conclusions by way of examples involving concrete composites. (The bronze sphere at 1045a26 is a prominent case.) A similar point is that Aristotle's discussion in the chapter's introduction refers to contact and stickiness as the cause of unity for some objects (at 1045a11-12). This leads Edward Halper, One and Many, pp. 179-180 to conclude that H6 must be concerned with composites: if it were primarily concerned with forms, he argues, Aristotle's examples involving contact and stickiness would be out of place. Now, Halper is correct that a discussion of the unity of objects by the contact or stickiness of different parts would have little relevance to the unity of form, assuming that forms are metaphysically simple. Readings that take Aristotle's principal explanandum to be the unity of forms, where forms are taken as simple, purely formal entities are therefore open to this objection. (9) But my reading is not troubled by this observation. The example involving stickiness is not out of place if Aristotle wishes to begin a discussion of unity by appeal to simple examples before moving on to more problematic cases whose unity is to be explained in a similar way. If, in other words, substantial forms themselves have parts, and material parts, as I shall argue they do, then they can be unified in a way analogous to everyday objects like the bronze sphere--not by stickiness, of course, but by something that allows for the unification of formal and material parts. As I see it, one key to understanding Aristotle's solution in H 6 is to notice that substantial forms are a type of composite object.


Immediately after the passage in which Aristotle presents the two problems of unity, he offers a solution: "But if, as we say, one element is matter and another is form, and one is potentially and the other actually, the question will no longer be thought a difficulty" (1045a22-24). If the analysis of the problems of unity just presented is correct, this ought to be the solution to both problems of unity, so that Aristotle means to solve both problems by an appeal to hylomorphism. (I discuss potentiality and actuality below.) This is possible only if forms are themselves composite entities and are unified in virtue of being part matter and part form. This reading, which seems to me to be the most natural one, has nevertheless been resisted by most commentators. David Bostock, for instance, argues that the problem of H 6 is initially formulated as relating to forms, but that Aristotle then has a change of heart and moves on to the problem of composites, a discussion which occupies the rest of the chapter. The solution involving hylomorphism is, on this reading, only directed at the problem of composites. (10) Other scholars, such as Halper, simply take the problem at issue to involve composites and Aristotle to be addressing this problem throughout the chapter. (11) I shall not comment in detail on these views, restricting myself instead to two interpretations. (i) The problem of H 6 concerns both forms and composites, and Aristotle solves both problems by means of hylomorphism. On this view, forms are themselves composite, and are unified in virtue of being part matter and part form. This is the view I advocate. (12) (ii) The problem of H 6 is primarily about forms, but in order to better elucidate the unity of forms, Aristotle first gives an explanation of the unity of composites. Hylomorphism, then, is introduced only to account for the unity of individual composites, whereas forms are unified in virtue of their metaphysical simplicity. This is Harte's reading, and it is the interpretation I will focus my criticism on.

First a point of agreement. As I have said, I agree with Harte that the main problem at issue H 6 is the unity of substantial form, and that H 6 is, to a large extent, dominated by what she calls a "dialectic with the Platonists". Starting from the argument at 1045a17-21, which Harte and I understand in the same way, Aristotle uses what he takes to be Platonist mistakes to present his own solution to the two problems of unity. But it is here that our readings begin to diverge. For Harte argues that after formulating both problems of unity, Aristotle turns immediately, at 1045a22-24, to his solution to the unity of composites. This solution, she argues, is a "useful primer" to his solution involving forms, and so is articulated first. The solution to the unity of forms comes only later, at 1045a36-b7, in a passage in which Aristotle discusses things with no matter whatsoever. In this way Harte concludes that forms are unified in virtue of their metaphysical simplicity, whereas composites are unified in virtue of possessing a unified form.

This reading is meant to respect the close connection Aristotle sees between the two problems, while still keeping them distinct. But it also has its problems. The first concerns Harte's view that the explanation of a composite's unity is its unified form, whereas the explanation of a form's unity is that it is ontologically simple and is one of a certain kind (a substance, quality, quantity, etc). A thing's being unified is therefore, in her view, closely connected to its being a thing of a certain sort, and 'unity' is equivocal just as 'being' is. In her view the two questions of unity are related because, "they both appeal to the explanatory bedrock of the unity of form" (1996, p. 298). The unity of a composite is, she argues, "parasitic" on the unity of its form, which is itself one in virtue of its simplicity. But Aristotle does not say that the solution to one will help us understand the other; he says that the two problems are the same ([TEXT NOT REPRODUCIBLE IN ASCII]). Specifically, he tells us that the problems of the unity of "round bronze" and the unity of man are the same problem:
 For this difficulty is the same as would arise if 'round bronze'
 were the definition of cloak; for this name would be a sign of the
 definitory formula, so that the question is, what is the cause of
 the unity of round and bronze? (1045a25-28)

Here Aristotle identifies the two problems of unity. He references the problem of composites by means of the example, a bronze sphere. The other "difficulty" is clearly the unity of forms. For Harte and I agree that the main focus of the chapter is the unity of substantial form, and unless Aristotle has had a change of heart, it is this problem that he identifies with the problem of unity for a bronze sphere. Thus, this passage claims that the problem of the unity of composites and of forms present the same problem. And if these problems are the same, then their solutions must be the same as well. This solution is hylomorphism. Therefore, the most natural way of reading the text is to take both the problems and their solutions to be the same, which is a far closer relationship than Harte would have it. (13) These reflections not only give us reason to doubt Harte's view; they also point towards the interpretation I favor: that the problem of unity of forms is to be solved by designating one of the two parts in its definition as matter, the other form. (14)

A second problem with Harte's reading is this: Aristotle tells us in H 6 that a logos must contain one part matter and one part form: "Of matter some is the object of reason, some of sense, and part of the formula ([TEXT NOT REPRODUCIBLE IN ASCII]) is always matter and part is actuality" (1045a34-5). The claim here seems to be that anything with a logos, and thus, anything with a definition, must be composite--with one part matter and the other actuality, or form. Call this the Principle of Definition (PD). PD implies that forms have one part matter and one part actuality (or form). Since substantial forms are definable, they have logoi, and so they must be composite, having formal and material parts. This, too, points to the reading that forms are unified in virtue of being matter-form composites. Harte, however, takes forms to be metaphysically simple, without material parts. So she must find a way to explain the remark away. Her response (Dialectic, p. 297) is that PD only applies to a kind of deficient or pseudo-definition, so that only a pseudo-definition need contain both formal and material parts. The reference to a logos, she argues, need not imply reference to a proper definition. She therefore rejects PD as applying to substantial forms, the entity she takes to be at the center of the discussion in H 6. On her reading, Aristotle does not mean to imply that the definitions of substantial forms must contain reference to both matter and form, but only the definitions of some other, degenerate entities.

This response is implausible on its face, since one would naturally expect the class of definitions to be a proper subset of the class of logoi. But leaving this aside, there is strong evidence that PD is meant to apply to the definitions of substantial forms. At the opening of our chapter, in what turns out to be a crucial passage, Aristotle announces that he is returning to the aporia previously stated "with respect to definitions and numbers" (1045a7-8). Now, Aristotle discusses definitions elsewhere in Z-H, but he discusses definitions in conjunction with numbers only in one place: H 3, 1043b32-1044a11. (15) And in H 3, in a passage immediately before the one referred to, we find the following:

[O]ne kind of substance can be defined and formulated, i.e. the composite kind, whether it be perceptible or intelligible; but the primary parts of which this consists cannot be defined, since a definitory formula ([TEXT NOT REPRODUCIBLE IN ASCII]) predicates something of something, and one part of the definition must play the part of matter and the other that of form. (1043b28-32, ROT modified) (16)

Here we have another, fuller statement of the claim that only a composite substance can be defined. According to this passage, given that substantial forms are definable, they must be composite: their definitions must have both formal and material parts. H 6's statement of PD, therefore, is not anomalous, and H 6 cannot be read as claiming that only a pseudo-definition must contain reference to both formal and material parts. It is also important to notice that at the beginning of H 6 Aristotle explicitly tells us that he is returning to a difficulty already addressed, and the reference is clearly to H 3, indicating that PD is operative in H 6. Thus, Aristotle's view in H 6 is that all definable things are composite. And, again, this implies that substantial forms are composite. Since substantial forms are definable - being essences, they must be (17)--their definitions must, on PD, have both formal and material parts. Just as the claim that the two problems of unity are the same gave us reason to reject Harte's view, the back-reference to H 3 strengthens the evidence against Harte's view and points us towards the reading that both problems of unity are to be solved by means of hylomorphism. (18)


We are now in a better position to understand the nature of the problem of H 6 and the controversy over the chapter's principal issue. I have argued that the chapter takes up both problems of unity and that the problem of forms has a certain primacy. But we have now seen that this is ultimately the same problem as that of the unity of composites and that both are to be solved via hylomorphism. One advantage of this reading is that it constitutes a rapprochement between the two camps of commentators. It is substantial forms, like man, that Aristotle seems most interested in, but since forms are themselves composite, his frequent use of composite entities as examples (the bronze sphere, things unified through stickiness, etc.), and his solution in terms of formal and material parts, should not surprise or trouble us. In a sense both camps are right: since forms are themselves composite, H 6 is concerned with both.

I have also presented Harte's interpretation that the problem of the unity of forms is solved later in the chapter with the claim that forms are metaphysically simple objects whose unity is guaranteed in virtue of their simplicity. I argued that this view does not square well with what is said and referenced in H 6. We have found instead that H 6 presents two closely related problems of unity, and then immediately goes on to solve both of them with the claim that composites and forms both have material and formal parts. Crucial texts turned out to be the claim that the two problems of unity are "the same" and a back-reference to a fuller statement of PD in H 3. We concluded that Aristotle means to solve the problem of the unity of substantial forms by appealing to their nature as composites of matter and form.

But Aristotle's solution is not complete; for it is not yet clear how hylomorphism helps to solve the problems of unity. In his solution Aristotle also makes use of potentiality and actuality, saying that matter is potential and form actual. The remainder of this section will sketch one way of understanding the relationship between potentiality and actuality in H 6: that they are to be understood correlatively, so that they reciprocally imply one another, and that no Aristotelian cause is needed to account for their unity. Our primary source for Aristotle's views on the unity of potentiality and actuality in H 6 is the following short, difficult passage:
 What, then, is the cause [[TEXT NOT REPRODUCIBLE IN ASCII]] of
 what is potentially being in actuality (discounting, in the case
 of a created thing, whatever produces it [[TEXT NOT REPRODUCIBLE
 IN ASCII]])? There is no further cause of the potential sphere
 being actually a sphere; this is precisely the essence for each
 of them. (1045a30-33, translation after Bostock, Aristotle) (19)

This passage, difficult as it is, certainly recognizes the role played by a craftsman or maker in explaining the unity of potentiality and actuality, but then it immediately sets it aside, saying that, "this is the essence of each". Several questions arise here, two of which I shall focus on. First, what is the antecedent of 'this'? What is the essence of each? And second, how many causes are needed for the unity of potentiality and actuality, and of what sort are they? The two questions are closely related, and I shall discuss them together. On the reading I will advance, the antecedent of "this" is "the potential sphere being actually a sphere", and only one cause is needed--the efficient cause of the craftsman.

On the question of the nature and number of causes, the brief summary at the end of H 6 helps to clarify Aristotle's view. There he says: "there is no other cause here [sc. for the potential and actual spheres to be one] unless there is something which caused the movement from potentiality into actuality" (1045b21-22, emphasis added). (20) The natural reading of this summary line is that aside from the efficient cause which causes the movement from potentiality into actuality--a clear reference to the craftsman--no other cause is needed to account for unity. This suggests that the earlier passage should be interpreted to mean that once we set aside the work of the craftsman, which we now see refers to an efficient cause, no further cause is needed to account for unity. The claim that "this is the essence of each" will therefore indicate not an additional Aristotelian cause but rather a way of understanding the relationship between the potential and the actual, such that they form a unity without the need for an additional aition. In the case of ungenerated entities, where no efficient cause is needed to unify matter and form, unity will be obtained without the need for any aition at all.

Harte also holds that the craftsman is a reference to an efficient cause, (21) but she gives different answers to the questions I asked above. She holds that the antecedent of "this" is "cause" and that a thing's form is what is responsible for its unity:

A composite is one because there is a unitary form which it exemplifies, and which its matter is potentially, its form is actually. A composite is one, then, because it is one something: that is, the unity of a composite is parasitic on the unity of the something it is, its form. Aside from the maker--that which, in the case of generated objects, brings about the unified realisation of form in matter--there is no other cause of a composite's unity: it is one because its form is one .... It is by seeing that, in the case of a composite, there is (aside from the maker) no other cause of its unity aside from its being a unified realisation of a unified form, that we see that, in the case of that unitary form, there is no other cause of its unity; it just is immediately one. (Harte, Dialectic, pp. 292-3)

Thus it seems that Harte finds two causes in our passage: an efficient one, which causes the "realisation of form in matter", and also a formal one, which--given her view that forms are one by nature--explains the unity of the composite. Many other scholars take a similar reading of the passage, perhaps in light of certain remarks from Metaphysics Z 17. (22) On such readings, the "essence of each" statement indicates that matter and form have the same essence, that of the actual sphere. (23)

I have already argued that this reading cannot be correct. The unity of a composite cannot be secured by reference to its unified form as Harte and others claim. Since all definable objects, including substantial forms, are definable, attempting to secure the unity of a composite by reference to its unified form would amount to securing the unity of a composite object by means of another composite. And this would, of course, only pose the same problem it was meant to solve. The summary passage at 1045b21-2 shows that the only aition needed to explain the unity of potentiality and actuality is an efficient one, not a formal or final one. So instead of interpreting potentiality and actuality by reference to the same essence, we should understand them by reference to one another, as correlative notions. (24)

And this is how I propose we understand the potentiality-actuality doctrine. Understanding it as Harte does would put all the explanatory power on the formal/actual part, and, as we have seen, this does not square with the text. The alternative--and here again I believe I follow Ross, Metaphysics, pp. 237-8--is to take the remarks on potentiality and actuality as a clue to understanding the matter--form relationship: as entities with correlative natures like that of potentiality and actuality. While no cause (aside from the efficient one) is needed to account for the unity of matter and form, understanding this unity requires understanding the reciprocal nature of matter and form. This is how I read the remark at 1045a33: both the potential and the actual sphere can be understood as the essence of the other. (25) Aristotle's point is not that the potential and actual spheres share the same nature--that of the form. Their natures are not the same; they are correlative: the bronze of a bronze sphere is by its nature the matter of that sphere, while the spherical shape is by its nature the form of it. The two are by their very nature united with one another. This is not the de dicto claim that an unformed piece of bronze will necessarily be fashioned into a sphere. Is it the de re claim that, when understood as the matter of that sphere, it is an essential part of the complex. Taking matter and form in this way, their compresence is sufficient to guarantee the unity of the composite object. In the case of generated things like the bronze sphere, this compresence has an efficient cause in the craftsman, whereas in ungenerated cases the two are naturally compresent. Understanding the nature of matter and form in terms of the potentiality-actuality doctrine helps us understand why compresence is enough. Once we have analyzed the object as a composite of matter and form, and in turn understood these as potentiality and actuality, and then mentioned the efficient cause (if there is one), unity is guaranteed and the problem is solved. (26)

Providing a full defense of this understanding of potentiality and actuality would take us too far afield, and deep into Metaphysics [THETA]. (27) So I shall only briefly make the case that the view we find in H 6 is that matter and form constitute an obvious, evident unity such that no (non-efficient) cause is required to explain it. Once matter and form are compresent, that is, the unity of the object they produce is evident, and no other cause of unity is needed. First, the language Aristotle uses to describe the problem suggests that once matter and form are understood properly as potentiality and actuality, the aporia is solved. The problem, he says, "disappears" ([TEXT NOT REPRODUCIBLE IN ASCII]: 1045a29), and this suggests that the nature of matter and form themselves is enough to explain their unity. Aristotle also alludes to the pointlessness of looking for a cause beyond the efficient one in the chapter's summary. He forswears the task of looking for another cause, since seeking the unity of matter and form is "like asking the cause of unity in general; for each thing is a unity, and the potential and the actual are somehow one" (1045b19-21). (28) So the question, Why are matter and form one? is to be dismissed, since having identified one as potential and the other as actual, the question does not arise. Aristotle's point is that in the case of substantial unities the question of why matter and form constitute a unity--where asking why is asking for an aition--can be dismissed as unnecessary. He is not claiming that there is absolutely nothing to be said to explain the unity, since an account of the correlative natures of potentiality and actuality will, of course, be needed. But as he insists in the chapter's summary, this will not constitute an additional aition. So H 6's potentiality-actuality doctrine, expressed by the enigmatic "this is the essence of either", means that the two essences are correlative such that the potential and the actual form a natural unity. Once we recognize that a substance like a bronze sphere consists of matter and form, the problem of unity is solved, as the matter and form imply one another. And although Aristotle is less than explicit on this point, we are made to believe that essentially the same solution applies in the case of man, defined as biped animal. Part of what it is to be an animal is to be potentially realizable as a biped; and part of what it is to be a biped is to be in actuality a realization of animal. Matter and form each have a sort of metaphysical hook that snares the other. The two are by their very natures united with one another. (29,30)


I have argued that form and matter both play an important role in Aristotle's solution to the unity of substantial form. The unity of man will consist in its material and formal parts being related so as to form a unity in a way similar to that of the matter and shape of a bronze sphere. The similarity between a bronze sphere and a biped animal consists in the fact that both possess formal and material parts, which when understood as potentiality and actuality will be seen to form a natural unity. In the case of the bronze sphere, it is easy to see how the bronze functions as the material element of the composite. But it is much harder to see in what sense biped animal can be said to possess a material element. If my reading is correct, Aristotle must have a conception of matter wide enough to allow the genus to be considered a type of matter, or at least to "play the role" of matter, as he says in H 3. As it happens, Aristotle does have a wider notion of matter than we do, and in H 6 he explicitly recognizes two types of matter, which he calls "intelligible" ([TEXT NOT REPRODUCIBLE IN ASCII]) and "perceptible" ([TEXT NOT REPRODUCIBLE IN ASCII]). Immediately upon making his claim about the aition of the unity of matter and form, he writes:

Of matter some is intelligible, some perceptible, and part of the formula is always matter and part is actuality, e.g. the circle is a plane figure. (1045a33-5, ROT modified)

Intelligible matter is also discussed in Z 10-11, where we are told, at 1037a2-5, that in the case of particular circles, the semi-circles that compose them will be parts of the circle as intelligible matter. (31) There are very few references to intelligible matter in the corpus, and there has been little discussion of it in the secondary literature. The only clear examples of objects with intelligible matter Aristotle gives are mathematical (at 1036a4, 1036a12 and 1037a2). This has led some scholars, including Harte, Dialectic, pp. 287-89, to conclude that the class of objects with intelligible matter is limited to mathematical objects.

This reading makes good sense of the examples in Z 10-11, but it is not clear that it is adequate to explain the reference in H 6. The two main protagonists in this debate are Ross and Rorty, and their main point of contention is over the question of whether only mathematicals possess intelligible matter (Rorty), or whether it also applies to the "generic element in a definition" and thus to universals (Ross). (32) Harte follows Rorty, arguing that: (a) in the two clear references to intelligible matter it is the matter of a mathematical object; and (b) the example given in H 6 is also a mathematical one. But Harte's arguments are not conclusive. With so little Aristotelian text devoted to intelligible matter, any interpretation is bound to be open to question. However, a good case can be made for Ross's view that in H 6 the genus of a substantial form is taken as intelligible matter. The fact that the example in H 6 is a mathematical one does not show what Harte thinks it does. Assuming it is original to Aristotle, (33) the example can be plausibly interpreted as mentioning only the genus of a circle, and so it can serve as an example of the genus as intelligible matter. The example again is "a circle is a plane figure." Now, "plane figure" can hardly serve as a definition for a circle, as it would not exclude other geometrical figures. But it does carve out a genus under which circles and other two-dimensional figures fall. The example does not include reference to the formal aspect which would be included in a definition. Thus we can interpret the example as specifying only the circle's genus, and the example now becomes pertinent not as a mathematical example but as a case of genus as intelligible matter.

On this reading, the discussion of intelligible matter, including the circle example, fits directly into the context of the chapter. By contrast, on the Rorty/Harte reading we are left to wonder why, if intelligible matter applies only to mathematical objects, Aristotle brings up intelligible matter in a chapter otherwise devoid of any discussion of mathematicals. Harte's answer is thoroughness: the reference "completes the discussion of the unity of composites by including intelligible objects" (p. 289), which, again, she identifies exclusively with mathematical objects. But this would make the reference something of a digression, given that Harte holds, as I do, that the chapter's principal explanandum is the unity of form. A better explanation, and one that fits the reference to intelligible matter squarely in the context of the chapter, is that intelligible matter applies to the very objects that are the focus of the chapter--substantial forms. Here again we find confirmation in H 3. Looking again at 1043b28-32, quoted above, we notice that Aristotle expresses PD with reference both to perceptible and intelligible objects. There is no reference to mathematical objects and no suggestion that intelligible matter is meant to apply only to mathematical objects or only to individuals. On the contrary, Aristotle seems to be making the general point that for all definable things, whether they are perceptible or merely intelligible, something must play the part of matter and something that of form. Thus, H 3 gives us no reason to think that only mathematicals possess intelligible matter; its apparent meaning is rather that for anything definable, there will be something playing the role of matter. (34) Returning to H 6, we again see PD expressed in terms similar to those in H 3. Both types of matter are referred to, and here, too, there is no suggestion that only mathematical objects are included in the class of things with intelligible matter. The reference to intelligible matter in H 6, then, is not made as an afterthought or merely for the sake of thoroughness. Instead, intelligible matter is of central importance to the discussion of the definition of substantial forms.

So there is good reason to think that in book H Aristotle understands the genus of substantial forms as a sort of matter. But there is also evidence for genus as matter elsewhere. The notion that genus is a sort of matter is the same sort of view entertained (though apparently not endorsed) in Z 12:
 If then the genus absolutely does not exist apart from the species
 which it as genus includes, or if it exists but exists as matter
 (for the voice is genus and matter, but its differentiae make the
 species, i.e. the letters, out of it), clearly the definition is
 the formula which comprises the differentiae. (1038a5-9)

Here, too, Aristotle is discussing the unity of form, and here he entertains the idea that a thing's genus exists apart from the species, but only "as matter." Since genera are intelligible, we can conclude that they exist as intelligible (not perceptible) matter. And this, I have argued, is precisely the view endorsed in book H. Taking the genus as matter fulfills the condition of PD that all definable things must include a material element.

A final passage comes from Metaphysics [DELTA] 24, where Aristotle is discussing the various senses of "coming from something" ([TEXT NOT REPRODUCIBLE IN ASCII]). The fourth sense is:
 As the form from its part, e.g. man from two-footed animal and
 syllable from letter; for this is a different sense to that in
 which the statue comes from the bronze; for the composite
 substance comes from the sensible matter, but the form also comes
 from the matter of the form [[TEXT NOT REPRODUCIBLE IN ASCII]].

There is no explicit reference to intelligible matter here, but given that forms are intelligible objects "the matter of the form" will be intelligible matter. These passages show that Ross's reading of intelligible matter in H 6 is not anomalous. In other parts of the corpus we find the genus understood as a type of matter.

This reading of intelligible matter fits the context of H 6 quite well. H 3, 1043b28-32, makes the claim that anything definable, whether perceptible or intelligible, must possess both form and matter. And in H 6, too, we find that Aristotle's solution to the problem of unity is articulated for both types of object. Here, again, we find a claim made in H 3 being echoed in H 6. What we find in H 6, then, is a brief but comprehensive account of the unity of matter-form composites, whether the matter is perceptible or intelligible. Objects with intelligible matter play a central role. Since PD applies to any definable object, merely intelligible (but definable) objects like substantial forms will possess intelligible matter. (35)

So much for intelligible matter. But Aristotle's taxonomy is still not complete, as he has yet to discuss objects with no matter whatsoever. So proceeding systematically, he next turns to these items:

But of things which have no matter, either intelligible or sensible, each is by its very nature essentially a kind of unity, as it is essentially a kind of being--a 'this',a quality, or a quantity. (1045a36-b2, ROT modified)

The end of this passage gives three examples of categories or summa genera --substance, quality, and quantity. But there is a question as to whether the things with no matter are the categories themselves, (36) or instead are objects falling under the categories. (37) Whatever they are, Aristotle tells us that, having no matter, they are by nature "essentially a kind of unity" ([TEXT NOT REPRODUCIBLE IN ASCII]) and "a kind of being" ([TEXT NOT REPRODUCIBLE IN ASCII]) (1045a36-b1). I have already noted that Harte reads this as Aristotle's solution to the problem of the unity of forms. She takes the description to refer to objects falling under the categories, like forms, relying in part on a claim following closely after this one, that "an essence is by its very nature a kind of unity as it is a kind of being" (1045b3-4). She reads this latter remark as claiming that essence in each category is essentially one and essentially a type of being. Essence in the category of substance is, of course, form, so on her reading this is Aristotle's answer to the main problem of H 6: forms are unified by being immediately, unanalyzably one.

The dispute turns on how to interpret the reference to an essence. And once again, our H 3 passage helps us understand matters: "... but the primary parts of which this [sc. substance] consists cannot be defined, since a definitory formula predicates something of something ..." (1043b30-1). The primary parts are the ultimate constituents of definable objects, and among these are the summa genera. And it is therefore the categories themselves that Aristotle is referring to, not objects falling under them. It is the categories which, having no matter, are indefinable, and being absolutely simple, are essentially beings and essentially unities. It is the categories which fit the description of "kinds of being", since Aristotle holds that "being" is equivocal between the various categories. The picture here is hierarchical. Take a concrete composite like Socrates. If he is definable, he will consist of form and matter. In this case, being sensible, his matter will be sensible. His form is man, which if it is definable will also consist of form (biped) and matter (animal), though in this case merely intelligible matter. Biped can also be analyzed into form and matter, but at some point, this process will cease, as substances are divisible finally into indivisible parts (1043b34-6). We have now reached the categories--in this case substance--which, because they are simple and have no genus above them, are not further analyzable. The categories cannot be divided into matter and form and are thus essentially one. "Being" cannot be said to reside in anything more general, so they are quite literally essentially types of being. These are the indefinable "primary parts" referred to in our H 3 passage.

The only bar to this hierarchical reading is a remark in H 6 which Harte takes as her cue: that an essence is by its nature a kind of being and a kind of unity (1045b3-4). Since essence in the category of substance is form, according to Harte it amounts to the claim that forms are by their nature unified beings. Ross translates and interprets this as a reference to the essence of each category. (38) Harte, Dialectic, pp. 289-90 counters by pointing out that the Greek simply says that an essence, not the essence of each category, is unified by its nature, and she charges Ross with over-translating. (39) This particular charge may be just, but when we read the passage in the context of H 3, we see that Ross's reading is nevertheless correct. H 3, it will be recalled, leaves an important place for the indefinable primary parts of definable substances. These primary parts--which are among the ultimate constituents of definable things--can only be the summa genera, and thus H 6 is claiming that the summa genera are immediately beings and immediately one. Harte believes an advantage of her interpretation is that it does not call for a digression into the unity of the categories. In fact, however, a parallel charge can be made against Harte's reading: Why does Aristotle mention the categories or the "primary parts" both in H 6 and in H 3, if his solution to the problem of unity does not rely on them? If Harte's reading were correct and a substance's unity were derived entirely from its (ontologically simple) form, the references to the primary parts of these substances in H 3 and the categories in H 6 would be irrelevant. They would play no role in the explanation of unity. But if, as I have argued, substantial forms are unified in virtue of their being matter-form composites, the unity of the categories is crucial. The unity of a substantial form must ultimately rest on something that is essentially, immediately one. The categories are thus brought in as part of the explanation for the unity of a form. Here too H 6 takes up and adds to a topic already discussed in H 3. In H 3 we are told that the primary parts of definable things are indefinable, and in H 6 we learn both that these primary parts are the summa genera and that they are essentially beings and essentially unities.

Let me now summarize my reading of this crucial middle part of the chapter. After presenting the problems of unity, Aristotle turns straightaway (at 1045a23) to his solution, which involves matter-form and potentiality-actuality. He then explains that the difficulty involving forms is the same as that involving a bronze sphere, saying that on his view the problem disappears. Then (at 1045a30) he explains the importance of potentiality and actuality, claiming that matter and form are reciprocal notions such that when compresent they guarantee unity. Then (at 1045a33) Aristotle distinguishes objects with perceptible matter from those with only intelligible matter, and generalizing his solution he applies it to these latter objects as well. This, I argued, is important because substantial forms are themselves composites of form and intelligible matter. And the unity of such substantial composites is further explained by means of Aristotle's analysis of matter as potentiality, form as actuality. Finally (at 1045a36) Aristotle turns to objects with no matter whatsoever, which he claims are unified in an unanalyzable and unproblematic way. Far from being his solution to the problem of unity of form, as Harte maintains, Aristotle here completes his discussion of unity by explaining the unity of the primary parts of which definable objects consist. These are the categories.


What I hope to have shown is that H 6 raises two problems of unity and solves them both by appealing to hylomorphism. Upon specifying that a thing is composed of matter and form, potentiality and actuality, and upon identifying the efficient cause, the problem of unity disappears. This analysis applies both to everyday composites like men, but also to substantial forms like man, with the only major difference being the type of matter involved. The unity of matter and form in a substantial complex like man is explained in terms of potentiality and actuality, which are to be understood correlatively. Matter is essentially the matter for its correlative form, while form is essentially the form for its proximate matter. This reading presents a unified picture of H 6 and respects its place in the context of book H, in which Aristotle consistently maintains that all definable things are composite. It is also a first step towards understanding the relationship between H 6 and Z 12, and thus towards a better understanding of the central books of the Metaphysics. (40)

DOI: 10.1515/apeiron-2012-0008


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(1) Calling Z-H a "two-book work" should not be taken to imply that the version of Z-H handed down to us is a fully unified work. I wish to bracket the questions concerning the relationship between Z and H as much as possible, though I accept the view, now widely held, that Z 7-9 and 12 were added later and that some further revision took place. See M. Frede and G. Patzig, Aristoteles: Metaphysik Z (Munich: C.H. Beck, 1988), vol. I, 24-6; M. Burnyeat, A Map of Metaphysics Z (Pittsburgh: Mathesis Publications, 2001), 29-38, 42-4; and D. Devereux, "The Relationship between Books Zeta and Eta of Aristotle's Metaphysics", Oxford Studies in Ancient Philosophy 25 (2003): 159-211.

(2) Some of the more important discussions of these issues are: D. Bostock, Aristotle Metaphysics Books Z and H [Aristotle] (Oxford: Clarendon Press, 1994), 279-290; M. Burnyeat et al., Notes on Books Eta and Theta of Aristotle's Metaphysics [Notes on Eta] (Oxford: Sub-faculty of Philosophy, 1984); D. Charles, "Matter and Form: Unity, Persistence, and Identity" [Matter and Form] in ed. T. Scaltsas et al., Unity, Identity and Explanation in Aristotle's Metaphysics (Oxford: Clarendon Press, 1994), 75-106; M.L. Gill, Aristotle on Substance: The Paradox of Unity [Substance] (Princeton: Princeton University Press, 1989), 138-44 and 168-70; E. Halper, One and Many in Aristotle's Metaphysics: The Central Books [One and Many] (Columbus: Ohio State University Press, 1989), 179-195; V. Harte, "Metaphysics H6: A Dialectic with Platonism" [Dialectic], Phronesis 41 (1996): 276-304; H.K. Kim, "Metaphysics H 6 and the Problem of Unity" [Problem], Journal of the History of Philosophy 46 (2008): 25-42; F. Lewis, "Aristotle on the Relation between a Thing and its Matter" [Relation] in ed. T. Scaltsas et al., Unity, Identity and Explanation in Aristotle's Metaphysics (Oxford: Clarendon Press, 1994), 247-278; F. Lewis, "Aristotle on the Unity of Substance" [Unity], Pacific Philosophical Quarterly 76 (1995): 222-265; M. Loux, "An Examination of Metaphysics H6" [Examination] in ed. May Sim, The Crossroads of Norm and Nature: Essays on Aristotle's Ethics and Metaphysics (London: Rowman & Littlefield, 1995), 247-79; R. Rorty, "Genus as Matter: Reading of Metaphysics Z and H" [Genus as Matter] in ed. Lee et al., Exegesis and Argument. Phronesis, supplementary vol. 1 (1973): 393-420; and W.D. Ross, Aristotle's Metaphysics [Metaphysics], vol. 2 (Oxford: Clarendon Press, 1924), 237-239.

(3) Scholars who take H.6 to be primarily concerned with forms include Bostock, Aristotle; Loux, Examination; Harte, Dialectic; and Rorty, Genus as Matter. Against them stand those who take the chapter to be concerned primarily with composites, notably Charles, Matter andForm; Gill, Substance, esp. pp. 138-144; Halper, One andMany, esp. [section]2.12; and Lewis, Relation.

(4) All English translations of Aristotle are from ed. J. Barnes, The Complete Works of Aristotle. Revised Oxford Translation (Princeton: Princeton University Press, 1984), unless noted otherwise.

(5) Cf. also 1045b7-17.

(6) Later in the chapter, at 1045b8-17, Aristotle returns to the problem and criticizes some attempted Platonist solutions.

(7) This suggestion was made in Notes on Eta and taken up by Harte, Dialectic, p. 284. I agree with Harte that H 6 means to solve both problems of unity, but as I explain below, we see the relationship between the two problems quite differently.

(8) Kim's, Problem, p. 27 understanding of the framework of H 6 is similar. She, too, argues that the chapter discusses both forms and composites, though she maintains that there is no priority in the discussion whatsoever: neither is the "exclusive, major, explanatory concern" of the chapter.

(9) Harte, Dialectic, in particular is open to this objection, since on her view the unity of forms is the primary focus of H 6, yet forms are unified simply by being one of a particular kind and ontologically simple, not by means of the coming together of separable parts. Gill, Substance, esp. p. 7 also seems to take forms in H 6 this way, but she holds that the chapter is concerned primarily with composites.

(10) Bostock, Aristotle, pp. 279-287. His interpretation depends on a highly controversial reading of 1045a20-22. He argues that the problem facing the Platonists is that they mis-define Man as "biped animal". This is based on an unlikely reading of the phrase "[TEXT NOT REPRODUCIBLE IN ASCII]" ["to define and to speak"] such that the kai is epexegetic and the whole phrase means simply "to define". But if the problem were simply a poor definition, why does Aristotle not offer a better one instead of analyzing it in terms of matter and form? And why does he single out the Platonists, who surely were not the only ones to define in such a way? The problem, as I see it, is not an incorrect definition--Aristotle, after all, makes use of the same definition with no apparent hesitation--but an incorrect understanding of what each part of the definition corresponds to. See Harte, Dialectic, pp. 282-3 for a more detailed discussion of Bostock's interpretation.

(11) Halper, One and Many, esp. pp. 179-180. One of the advantages of my interpretation is that it provides an easy explanation for why just after presenting a problem for the unity of forms, Aristotle goes on to discuss matter-form composites.

(12) Following Ross, Metaphysics, pp. 237-8.

(13) Gill's, Substance, view suffers from a difficulty similar to Harte's, since Gill takes the two problems to be only imperfectly analogous. Since the text claims that the two problems of unity are the same, both readings are suspect.

(14) One might object that Aristotle's solution to the problem of the unity of form is perhaps not quite the same as his solution for composites, because the material aspect will be different. As I argue below, the genus in the definition of a substantial form is intelligible matter, while the matter of a concrete composite is perceptible matter. Aristotle takes his hylomorphic solution to the problem concerning composites to be the more intuitive one, and he uses his solution to this problem to illuminate his solution to the other. But as both solutions involve the same relationship between matter and form, potentiality and actuality, calling the solutions "the same" is justified.

(15) Ross, Metaphysics, in his note ad loc. cites 1044a3 in particular as the line Aristotle has in mind when he returns to the difficulty in H 6; Notes on Eta cites 1044a3-6.

(16) Cf.also H2, 1043a5-7.

(17) Though Kim, Problem, p. 28 apparently reads H3, 1043b10-14 as rejecting the possibility of defining substances. But the passage in no way precludes this--it only tells us that a proper account of man must refer both to man's matter and to its substance (ousia).

(18) For a clear indication that Aristotle holds that forms possess matter, see Met. [DELTA] 24, 1023a35-b2, which I quote below.

(19) The text of 1045a31-33 has: "[TEXT NOT REPRODUCIBLE IN ASCII]".


(21) Harte, Dialectic, pp. 292-3 and note 44. Ross's, Metaphysics, note ad loc. and Notes on Eta also see an efficient cause at work.

(22) Including Burnyeat, Notes on Eta; Charles, Matter, pp. 88-90; and Lewis, Relation, pp. 254- 5 note 20. Charles and Lewis see the cause as both a formal and a final one.

(23) Charles, Matter and Form, pp. 88-9 (and Lewis, Unity, note 55 cites him approvingly) argues that in the summary passage cited above (1045b21-2) Aristotle ought to be read as excluding as a cause only what is "distinct from the relevant actuality and potentiality" (emphasis in original). This allows Charles to read the summary passage as making room for a formal/final cause, thereby making it consistent with his reading of the earlier passage (1045a30-33) in which he also finds a formal/final cause. But this is an unlikely reading, because, as Charles himself grants, the summary passage is clear in its disavowal of any cause save the efficient one. Charles writes that, "... the final sentence [of the summary passage] clearly says that there is no other cause of the unity of what is potentially F and what is actually F apart from the efficient cause" (p. 88, emphasis in original). Thus, even Charles grants that in the summary at the end of H 6 Aristotle's claim is that only an efficient cause is needed for unity. And because this summary passage is clearer than the earlier statement at 1045a30-33, it should be used to interpret the earlier statement, rather than the other way around. The best reading, therefore, is that only the efficient cause is necessary. Still, I agree with the spirit of much of Charles's discussion, as we both hold that the theory behind actuality and potentiality is necessary for a full explanation of unity. We differ on whether H 6 recognizes this as an aition.

(24) It might be objected that there is a logical gap in the argument as I have presented it. I have argued that:

(1) Definitions must have both formal and material parts.

(2) Forms are definable.

So, (3) Forms must have both formal and material parts.

But this conclusion does not follow, because I have not argued that:

(4) If all definitions have both formal and material parts, then all definable things must have formal and material parts. This gap is exploited by Kim, Problem, who argues that forms have parts nominally but are in fact metaphysically simple. This is an ingenious move, but H 3 again proves to be crucial evidence against it, as it clearly indicates that all definable things must be matter-form composites. See esp. H 3, 1043b28-32: "one kind of substance (ousia) can be defined and formulated, i.e. the composite kind", whereas a substance's incomposite primary parts cannot be. Cf. also Z 10, 1034b20-24: "Since a definition is a formula, and every formula has parts, and as the formula is to the thing, so is the part of the formula to the part of the thing, we are already faced by the question whether the formula of the parts must be present in the formula of the whole or not". The implication is that the parts of a thing's definition correspond to the thing's parts, so that a definition's formal and material parts will correspond to the defined object's formal and material parts.

(25) Ross, Metaphysics, pp.237-8 also recognizes the importance of both sets of notions, though his analysis is rather vague: "the proximate matter and the form are one, the first being potentially what the second is actually, so that there is no reason of their unity except that which causes the movement from potentiality to actuality".

(26) My reading of the matter-form relationship in H 6 rejects the "identity model", held by W. Sellars, "Aristotle's Metaphysics: An Interpretation" in his Philosophical Perspectives: History of Philosophy (Springfield: Ridgeview Publishing Company, 1967), 73-124; R. Rorty, Genus as Matter; A. Kosman, "Animals and Other Beings in Aristotle" in edd. Gotthelf and Lennox, Philosophical Issues in Aristotle's Biology (Cambridge: Cambridge University Press, 1987), 360-391; and Kim, Problem, in which matter/potentiality and form/actuality are taken to be identical. The concluding summary of H 6 says that potentiality and actuality are "one and the same" [[TEXT NOT REPRODUCIBLE IN ASCII]] (1045b18-19) and "somehow one" [[TEXT NOT REPRODUCIBLE IN ASCII]] (1045b21). However, these remarks should not be taken to indicate identity. The remark that they are "somehow one" suggests not strict identity but a hedge. We might also notice that in the summary Aristotle tells us, referring back to 1045a30-33, he has "already said" that form and matter are one. 1045a30-33 is the passage in which he claims that there is no other cause for unity, but this is the essence of each. There is no suggestion in this passage that potentiality and actuality are identical. Cf. also Loux, Examination.

(27) Cf. also the discussion in H 5 and J. Beere, Doing and Being: An Interpretation of Aristotle's Metaphysics Theta (Oxford: Clarendon Press, 2009); A. Code "Changes, Powers and Potentialities in Aristotle" in ed. N. Reshotko, Desire, Identity, and Existence: Essays in Honor of T.M. Penner (Edmonton: Academic Print & Pub, 2003), 251-271; and L.A. Kosman, "Substance, Being, and Energeia", Oxford Studies in Ancient Philosophy 2 (1984): 121-149.

(28) De Anima II 1, 412b6-9 makes the same point with body and soul standing in for matter and form.

(29) Part of what Aristotle is assuming, I take it, is a point he shares with the Platonists: that animals are naturally divisible (or perhaps: "realizable") into, say, bipeds and non-bipeds, rather than into, say, hairy and hairless. Calling something potentially or actually an x is thus to make a metaphysical and not merely a modal claim about it. Whereas (an) animal is both possibly bipedal and hairy, it is potentially bipedal but not potentially hairy. The point is made explicitly in the discussion of definition in Z 12, where we are told (at 1038a12-15) that it is proper to divide the footed into cloven-footed and non-cloven-footed rather than winged and wingless. This makes Aristotle's example of the bronze sphere to make a point about potentiality rather misleading, since it might be taken to suggest that a division of bronze objects will result in spheres as one of a set of natural classes, just as the natural division of animals will result in bipeds and non-bipeds. The advantage of the example, on the other hand, is that it is a case of a matter-form composite whose unity is not in question, and this seems to be the main point of analogy. I am grateful to Dominic Scott for discussion on these issues.

(30) This reading of H 6 contrasts with a natural reading of Z 17, 1041b11ff., in which a composite's form is responsible for its unity. This might be taken to favor a view similar to Harte's, though in contrast to Harte's reading of H 6, Z 17 does not present form as metaphysically simple. Now, I have argued that this view of form is inconsistent with both: (i) PD taken with the definability and form, and with (ii) Aristotle's claim that at most an efficient cause is needed to account for unity. It is also difficult to square with the notion that we can dismiss the question of why matter and form are one, once potentiality and actuality are properly understood. So if my reading of H 6 is correct, then H 6 seems to be inconsistent with Z 17 (and perhaps also with Z 12). This might lead one to add weight to certain interpretations of H 6, but if we focus on H 6 along with its clear back-reference to H 3, the evidence seems to me to strongly favor my reading over Harte's. In fact, all of book H is consistent on (i) and (ii). Any attempt to explain these apparent inconsistencies would involve a long digression into the relationship between Metaphysics Z and H, a major topic in its own right. The result would be a different and much longer essay.

(31) Intelligible matter is mentioned explicitly in Metaphysics Z only twice: at 1036a9-10 and 1037a4-5. There are a few other, similar references without the adjective [TEXT NOT REPRODUCIBLE IN ASCII]: Metaphysics [DELTA] 24, 1023b1-2, Z 12, 1038a5-9; and I 8, 1058a23-4. Harte, Dialectic, p. 288 note 31 mentions another at De Anima 429b18-20.

(32) Cf.Rorty, Genus as Matter; Ross, Metaphysics, notes on 1036a9-10 and on 1045a34; and Bostock, Aristotle, note on 1045a33-5.

(33) There is some doubt. It does not appear in Pseudo-Alexander's commentary, and Jaeger, Aristotelis Metaphysica (Oxford: Clarendon Press, 1957), note ad loc. brackets it as a gloss.

(34) The following passage (1043b32ff.) does mention numbers. But the focus of the passage is clearly on the definition of substances, which are compared to numbers.

(35) Cf. Ross's, Metaphysics, notes on Z 10, 1036a9-10 and H 6, 1045a34ff.Ross writes that in Met. Z intelligible matter is restricted to non-perceptible individuals or in sensible individuals not qua perceptible, but that the notion takes on a wider meaning in Met. H. This wider conception, he continues, is not restricted to individuals but refers to the generic element in a definition. I agree, except to add that the passages quoted above show that the conception of genus as intelligible matter is not confined to book H. Ross, in his note on 1036a9-10 attempts to harmonize these two notions of intelligible matter, but because of space constraints I cannot comment further on the matter.

(36) As in Ross, Metaphysics; Rorty, Genus as Mattter; and Notes on Eta.

(37) As in Bostock, Aristotle, p. 285, and Harte, Dialectic, pp. 289-90. Gill, Substance, pp. 168-9 takes a different view. She claims that the passage describes the unity of an ordinary genus and differentia--a case in which the genus is conceptually included in the differentia. In such cases, she suggests, there is no matter to account for. The rest of my discussion should make it clear why I believe this reading is mistaken.

(38) Ross's original translation, The Works of Aristotle Translated into English (Oxford: Oxford University Press, 1928) has "and the essence of each of them is by its very nature ..." (emphasis added). Cf. the note ad loc. in Ross's Metaphysics and Notes on Eta.


(40) Earlier versions of this paper were presented at Fordham's International Conference on Ancient and Medieval Philosophy, the University of Virginia, and the APA Pacific Division. I am grateful to the audiences at these events and to my APA commentator, Scott O'Connor. Special thanks go to Dan Devereux, who provided invaluable comments and discussion on earlier versions of this paper.


Corcoran Department of Philosophy

University of Virginia
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Author:Keeling, Evan
Publication:APEIRON: A Journal for Ancient Philosophy and Science
Date:Jul 1, 2012
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