Aristotle famously contends that every physical object is a compoundof matter and form. This doctrine has been dubbed“hylomorphism”, a portmanteau of the Greek words formatter (hulê) and form (eidos ormorphê). Highly influential in the development ofMedieval philosophy, Aristotle’s hylomorphism has also enjoyedsomething of a renaissance in contemporary metaphysics.

While the basic idea of hylomorphism is easy to grasp, much remainsunclear beneath the surface. Aristotle introduces matter and form, inthePhysics, to account for changes in the natural world,where he is particularly interested in explaining how substances comeinto existence even though, as he maintains, there is no generationex nihilo, that is that nothing comes from nothing. In thisconnection, he develops a general hylomorphic framework, which he thenextends by putting it to work in a variety of contexts. For example,he deploys it in hisMetaphysics, where he argues that formis what unifies some matter into a single object, the compound of thetwo; he appeals to it in hisDe Anima, by treating soul andbody as a special case of form and matter and by analyzing perceptionas the reception of form without matter; and he suggests in thePolitics that a constitution is the form of apolisand the citizens its matter, partly on the grounds that theconstitution serves to unify the body politic.

Hylomorphism thus finds a range of applications acrossAristotle’s corpus. This entry focuses on its genesis anddevelopment in thePhysics andMetaphysics, in orderto characterize and assess its fundamental features and corecommitments. There is in any case already a considerable controversyat this basic level about what Aristotle means by matter and form:what precisely they are, how they are related to one another, howAristotle intends to marshal arguments in support of them, and howbest to deal with reasonable objections to their metaphysicalconsequences. We will begin by examining how Aristotle introduces histwin notions. Then we will move on to discuss some of the mostimportant interpretative controversies: does Aristotle believe inso-called “prime” matter? Does matter or form serve as theprinciple of individuation in his metaphysics? Do natural formsinclude a specification of the kind of matter that anything of thatform has to have?

• 1. Matter and form introduced
• 2. Prime matter
• 3. The principle of individuation
• 4. Matter-involving forms
• Bibliography
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1. Matter and form introduced

Aristotle introduces his notions of matter and form in the first bookof hisPhysics, his work on natural science. Natural scienceis concerned with things that change, and Aristotle divides changesinto two main types: there are accidental changes, which involveconcrete particulars, or “substances” (ousiai) inAristotle’s terminology, gaining or losing a property (seeCategories 1–5,Physics i 7). For instance,the changes whereby Socrates falls in a vat of dye and turns blue, orputs on a few pounds from excessive feasting during the Panathenaia,count as accidental changes (in the categories of quality andquantity, respectively). Socrates, a substance, gains the property ofbeing blue, or the property of weighing twelve stone. The other mainkind of change is substantial change, whereby a substance comes into,or passes out of, existence. For example, when Socrates dies, or isborn (or perhaps conceived, or somewhere in between conception andbirth), a substantial change has taken place.

Matter and form are required to account for this second kind ofchange, if it is to conform to Aristotle’s general conceptualanalysis of change. In any change, he contends, there must be threethings: (1) something which underlies and persists through the change;(2) a “lack”, which is one of a pair of opposites, theother of which is (3) a form acquired during the course of the change(Physics i 7, 190a13–191a22). Thus, for example, in anaccidental change, the underlying thing is the substance whichacquires a new accidental property. For instance, when Socrates learnsto play the flute, he transitions from a state of being unmusical (thelack) to a state of musicality (the form). But for us to be able tosay that there is something which has changed, there must be somethingwhich remains the same throughout the change, and in this case theobvious candidate is Socrates, who is one and the same personthroughout his musical training.

In accidental changes there is always a substance to underlie thechange, but this is not true for substantial changes, since theseinvolve the coming to be or passing away of a substance (see theamusing remark of Irving Copi, quoted at the start of the entry onidentity over time). In these cases, the thing that underlies is the matter of thesubstance. When someone builds a house, it is the bricks which persistthrough the change. They transition from a state of not being a houseto acquire the property of being a house. Aristotle often uses theexample of artefacts like houses, even though he does not regard themas substances properly-speaking (Metaphysics vii 17,1041b28–30), because their matter is more straightforward toidentify. Nevertheless, the same analysis holds in the case oforganisms, which are the substances proper: when an organism iscreated or destroyed, when an acorn becomes an oak tree, or a humandies, there must be some matter which persists through the change. Tosay otherwise would be to say that things can come to be out of, orvanish into, nothing, and Aristotle understandably agrees with hispredecessor Parmenides that this is impossible (Physics i 8,191a23–b17). Aristotle’s metaphysics takes as its startingpoints observed phenomena, and seeks to preserve common sense beliefswhere possible. We never experience anything simply appearing ordisappearing at random.

The word “form” may misleadingly suggest that what isacquired in a case of substantial generation is simply a shape, andthis impression is reinforced by some of the examples that Aristotleuses, especially when focusing on artefacts: plausibly the form of abronze statue just is its shape. When we consider organisms, however,it becomes apparent that having the right shape is not sufficient topossess the form. A thing’s form is its definition oressence—what it is to be a human being, for example. A statuemay be human-shaped, but it is not a human, because it cannot performthe functions characteristic of humans: thinking, perceiving, moving,desiring, eating and growing, etc. The connection between athing’s form and its function emerges inPhysics ii 3,where Aristotle distinguishes his four kinds of cause: material,formal, efficient, and final, and suggests a special connectionbetween the formal and final cause.

Here one needs to proceed cautiously, however, since it is sometimessaid that Aristotle’s word “cause” (aitia)would be better translated as “explanation” (or“explanatory factor”, to avoid the implication that theyare linguistic items, as opposed to things-in-the-world). Certainlymodern philosophers tend to use “cause” in a narrower way,which approximates to Aristotle’s efficient cause.Aristotle’s idea is that there are four kinds of thing that needto be mentioned in order to give a full account of the nature of anobject, each corresponding to a particular kind of question. We needto know what the thing is made of, and the answer to this question isthe thing’s matter—bricks, in the case of a house; bodilyorgans in the case of a human being. Next we need to know what thething is, or how it is defined, and the answer to this is thething’s form or essence. We also need to know what made thething come into existence, who or what created it, and this is thething’s efficient or “moving” cause. Lastly, we needto know what the thing is for, what its purpose or functionis—the final cause. Now Aristotle observes that, although theseare all distinct questions, in the case of the last three very oftenthe same thing will serve as the answer to all of them(Physics ii 7, 198a24–27). A house is defined as ashelter of a certain sort (De Anima i 1, 403b3–7;Metaphysics viii 3, 1043a29–36). That is what a houseis, i.e., its formal cause, but it is also what a house isfor, its final cause, since houses, like all artefacts arefunctionally defined. Similarly, a human being is defined as somethingwhich lives a certain kind of rationally-directed life. But, onAristotle’s view, this is also what a human being is for. Thehuman function is to live such a life (Nicomachean Ethics i7, 1097b22–1098a20; cf.De Anima ii 1, 412a6–22).As for the efficient cause, it is qualitatively, although notnumerically, identical with the formal cause, at least in the organismcase, since human beings give birth to human beings, and the same goesfor all other living things. Thus, even though Aristotle admits fourdifferent kinds of cause, in a sense it is only really matter and formthat play any ineliminable explanatory role in his system.

In fact, Aristotle does not simply focus on the case of artefactsbecause their pre-existing matter iseasier to identify.There is a particular issue here with the case of organisms, whicharises out of Aristotle’s insistence that a human being, forinstance, is composed of a rational soul, which is the form, and anorganic body, which is the matter (for further discussion of thisproblem, see Ackrill 1972/73). It is characteristic of the matter ofartefacts that numerically the same stuff which makes up one objectcan later be used as the matter of another: for instance, when onemelts down a bronze statue, and then molds it into some jewelry, it isthe same bit of bronze throughout. It is crucial that a thing’smatter can survive such changes, if it is to play the role thatAristotle needs it to play in cases of substantial generation anddestruction, as being the thing that underlies such changes. If anartefact’s matter only contingently has the form it has, thesame does not obviously seem true of organisms. Unlike in the case ofa house built from bricks, it does not seem as though one’s bodypredates one’s existence, and so can serve as the underlyingthing in a case of substantial generation. One might think that atleast the body does exist after death, but in fact Aristotle woulddisagree. Instead, he insists that a dead body is only“homonymously” called a body—that it is onlydescribed as “a body” by extension, because itsuperficially resembles a living body (De Anima ii 1,412b10–25;Metaphysics vii 10, 1035b9–25). It isnot a real body, because it is incapable of performing the functionsnormally associated with bodies, just as a statue’s eye, or aneye in a painting, is not a real eye, because it is made of stone orpaint, and thus cannot serve the function that genuine eyes existfor—seeing (for further discussion, see the supplement to theentry on Aristotle’s psychology ona fundamental problem about hylomorphism).

It might seem that Aristotle is rather going against ordinarylinguistic usage here, since we in fact regularly do refer to deadbodies as “bodies”. Whether a dead body is really a bodymight seem like a trivial linguistic issue, which can simply bedecided by fiat. The obvious way to resolve the problem might seem tobe simply to drop the insistence that the body cannot exist withoutbeing coupled to a living human soul. Allowing that a dead bodyremains the same body as its living counterpart will not help thedifficulty of what to say about the matter that predates the coming tobe of the organism, when there is no apparent body, living or dead.What is more, Aristotle is deeply committed to his position that thehuman body is essentially ensouled, because of his view that thingsare defined by their functions (Meteorologica iv 12,390a10–15;Generation of Animals ii 1,734b24–31).It seems as though he believes that a human being’s matter mustbe contingently alive, so that it can serve as the underlying thingthat remains when the human being comes into existence, but also thatit must be essentially alive, because it is functionally defined. Ifso, he contradicts himself.

The best way to resolve this apparent contradiction inAristotle’s hylomorphism is to point out that an organism canhave more than one level of matter. Aristotle believes that allsensible substances can be analyzed into matter and form, but such ananalysis is not restricted to the things he calls substances. Mattercan itself be divided into matter and form: for instance, bricks aremade of clay, shaped into cuboid blocks. Again, clay has its ownmatter—mud, say—and so on. Eventually, if one pursues thishierarchy of matter far enough downwards, Aristotle believes that onewill reach the four elements, earth, air, fire and water. He agreeswith Empedocles that everything in the sub-lunar world is ultimatelymade up of different ratios of these four elements. Matter then shouldreally be understood as a relative notion—it is always thematterof something. Aristotle distinguishes between athing’s proximate matter, the stuff it is most immediately madeof, and its less proximate matter, i.e., the matter of its matter, oreven further down the hierarchy, culminating in its ultimate matter,the elements. The organic body which is a human being’sproximate matter is essentially alive, but this need not apply to allof the other matter further down the chain. Aristotle distinguishesbetween homoiomerous and heteromerous parts (Parts of Animalsi 1, 640b25–30). Homoiomerous parts are stuffs, like bronze orflesh, which Aristotle believes have no internal structure. Every partof a homoiomerous stuff is the same as every other part, containingthe same ratio of elements. This view of homoiomerous parts isconsistent with Aristotle’s denial of atomism; he believes thatmatter, as well as space and time, are infinitely divisible. Thebodily organs, hands, feet, eyes, hearts, etc., are heteromerous,since they do have internal structure, with different parts of themmade up of different stuffs. A person’s hand, for instance, ismade of flesh, bones, blood and other such biological matter, which inturn are made of earth, air, fire and water. It may be that flesh toois functionally defined, so that dead flesh is only called“flesh” homonymously as well. Even if nothing biologicalcan exist when not alive, it seems clear that the elements at leastmust be able to do so. Therefore there will be some, low-level matterto serve as the thing that underlies the coming to be and passing awayof organisms, even though an organism’s proximate matter existsfor precisely as long as it does.

2. Prime matter

One obvious question pertains to how low such underlying levels mightgo. In fact there is considerable controversy concerning how toconceive the bottom rung of Aristotle’s hierarchy of matter.Aristotle believes that everything is made of earth, air, fire andwater. These elements are defined by their possession of one of eachof the two fundamental pairs of opposites, hot/cold and wet/dry.Aristotle also thinks that these elements can change into one another(On the Heavens iii 6, 305a14–35). If his analysis ofchange is correct, when some water changes into some air, there mustbe something underlying, some substrate, which persists through thechange, initially having the essential properties of water (being wetand cold, on Aristotle’s view) and then later those of air(being wet and hot). The thing that underlies this kind of changecannot be any of the elements, since it must be capable of possessingthe properties characteristic of each of the elements successively,capable of being first cold and then hot, for example. The traditionalinterpretation of Aristotle, which goes back as far as Augustine(De Genesi contra Manichaeos i 5–7) and Simplicius(On Aristotle’s Physics i 7), and is accepted byAquinas (De Principiis Naturae §13), holds thatAristotle believes in something called “prime matter”,which is the matter of the elements, where each element is, then, acompound of this matter and a form. This prime matter is usuallydescribed as pure potentiality, just as, on the form side, the unmovedmovers are said by Aristotle to be pure actuality, form without anymatter (Metaphysics xii 6). What it means to call primematter “pure potentiality” is that it is capable of takingon any form whatsoever, and thus is completely without any essentialproperties of its own. It exists eternally, since, if it were capableof being created or destroyed, there would have to be some even lowermatter to underlie those changes. Because it is the matter of theelements, which are themselves present in all more complex bodies, itis omnipresent, and underlies not only elemental generation anddestruction, but all physical changes. As a completely indeterminatesubstratum, prime matter bears some similarities to what modernphilosophy has called a “bare particular” (see Sider2006), although, not being a particular, it may have more in commonwith so-called “gunk” (see Sider 1993).

A similar idea is to be found in Plato’sTimaeus,49–52, where, in addition to his Forms and the particulars whichinstantiate them, he argues for the existence of a third category ofthing, “a receptacle of all coming to be”(49a5–6):

it must always be called by the same term. For it does not depart fromits own character at all. It both continually receives all things, andhas never taken on a form similar to any of the things that enter itin any way. For it is laid down by nature as a recipient ofimpressions for everything, being changed and formed variously by thethings that enter it, and because of them it appears different atdifferent times. (50b6–c4)

Plato also motivates his receptacle by appealing to the phenomenon ofthe elements changing into one another, and, although he refers to itas “space” and not “matter”, the traditionalinterpretation has it that, as he often does, Aristotle has adopted anidea first developed by his mentor.

More recently, opponents of attributing a doctrine of prime matter toAristotle have complained that there is insufficient evidence for hisholding this kind of view, and that it is so philosophicallyunappealing that principles of charity militate against it as aninterpretation. Such scholars point out that Aristotle actuallycriticizes Plato’s account from theTimaeus, inOnGeneration and Corruption ii 1:

what Plato has written in theTimaeus is not based on anyprecisely-articulated conception. For he has not stated clearlywhether his “Omnirecipient” exists in separation from theelements; nor does he make any use of it. (329a13–15)

Although Aristotle is clearly criticizing Plato here, it may be thathis point is simply that Plato was not sufficiently clear that primematter is never to be found existing apart from the elements, and thathe did not give good enough reasons for its introduction, not that hewas wrong to believe in it.

In this connection it is appropriate to note that Aristotle does infact use the expressions “prime matter”(prôtê hulê) and “primary underlyingthing” (prôton hupokeimenon) several times:Physics i 9, 192a31, ii 1, 193a10 and 193a29;Metaphysics v 4, 1014b32 and 1015a7–10, v 6,1017a5–6, viii 4, 1044a23, ix 7, 1049a24–7;Generationof Animals i 20, 729a32. The mere fact that he uses the phrase isinconclusive, however, since, he makes it explicit that “primematter” can refer either to a thing’s proximate matter orto whatever ultimately makes it up:

Nature is prime matter (and this in two ways, either prime in relationto the thing or prime in general; for example, in the case of bronzeworks the bronze is prime in relation to them, but prime in generalwould be perhaps water, if everything that can be melted is water).(1015a7–10)

Here Aristotle is referring to his predecessor Thales’ view thateverything is ultimately made of water, which he in fact rejects.

In other passages too Aristotle seems to leave the question of whetheror not there is prime matter deliberately open. InMetaphysics ix 7, he uses a conditional to talk about thepossibility:

it seems that what we call not this, but that-en—for example, wecall the box not wood, but wooden, nor do we call the wood earth, butearthen, and again earth, if it is this way, we do not call somethingelse, but that-en—that is always potentially withoutqualification the next thing…Butif there is somethingprimary, which is no longer called that-en with respect to somethingelse, this is prime matter. For example, if earth is airy, and air isnot fire but firey, fire is prime matter, being a this.(1049a18–22…24–27)

Here Aristotle uses the generic adjective “that-en”(ekeininon), a word that he coins, to mean made ofthat material. If a material could not be so described, itwould be prime matter. Again, he shows himself aware of prime matteras a possibility, without wanting to commit to it here.

Another key passage where Aristotle has been thought to commit himselfmore decisively to prime matter isMetaphysics vii 3. Here weare told:

By “matter” I mean that which in itself is not called asubstance nor a quantity nor anything else by which being iscategorized. For it is something of which each of these things ispredicated, whose being is different from each of its predicates (forthe others are predicated of substance, and substance is predicated ofmatter). Therefore this last is in itself neither substance norquantity nor anything else. Nor is it the denials of any of these; foreven denials belong to things accidentally. (1029a20–26)

Although the word “prime” does not occur here, Aristotleis evidently talking about prime matter. A natural way to read thispassage is that he is saying there is a wholly indeterminateunderlying thing, which he calls “matter”, and it is not asubstance. Those who wish to avoid attributing a doctrine of primematter to Aristotle must offer a different interpretation: that if wewere to make the mistake of regarding matter, as opposed to form, assubstance, we would be committed (absurdly) to the existence of awholly indeterminate underlying thing.

In addition to disputing the correct interpretation of these passageswhere Aristotle explicitly mentions prime matter, much of the debatehas centered around, on the one hand, whether what he says aboutchange really commits him to it, on the other, whether the idea isreally absurd. Some opponents of prime matter have argued thatAristotle does not, after all, wish to insist that there is alwayssomething which persists through a change (see Charlton 1970,Appendix, and 1983). In particular, when one of the elements changesinto another, there is an underlying thing—the initialelement—but in this case it does not persist. They point outthat in the key passage ofPhysics i 7, where Aristotle giveshis account of change in general, he uses the expressions“underlying thing” and “thing that remains”.While readers have usually supposed that these terms are usedinterchangeably to refer to the substance, in cases of accidentalchange, and the matter in substantial changes, this assumption can bechallenged. In the elemental generation case, perhaps there is nothing that remains, just an initial elements that underlies. The worryabout this interpretation is whether it is consistent withAristotle’s belief that nothing can come to be out of nothing.If there is no “thing that remains” in a case of elementalgeneration, how is an instance of water changing into air to bedistinguished from the supposedly impossible sort of change wherebysome water vanishes into nothing, and is instantly replaced by someair which has materialized out of nothing?

The main philosophical objections to prime matter are that it is, atbest, a mysterious entity that we cannot know anything about, since wenever perceive it directly, but only the things it underlies. Ofcourse, there can be good theoretical reasons for believing in thingsthat we never actually see. No one has ever seen a quark, but we canstill know things about them, based on the kind of theoretical workthat they are required to perform. Still, Aristotle’s theorywill be more parsimonious, if he can manage without positing suchtheoretical entities. At worst, prime matter is said to be outrightcontradictory. It is supposed to be capable of taking on any formwhatsoever, and thus to have no essential properties of its own. Theidea that it has no essential properties of its own seems to make itdifficult for us to characterize it positively in any way: how can itbe invisible, or eternal, or the ultimate bearer of properties, ifthese are not properties that belong to it essentially? Moreover, ifit is what ultimately underlies all properties, it seems that it mustbe able to take on properties that are inconsistent with what we wouldlike to be able to think of as its own nature: when Socrates turnsblue, there is also some prime matter that underlies him, which alsoturns blue. But how can prime matter be simultaneous invisible andblue? To get around these problems, it looks as though proponents ofprime matter will have to distinguish between two different kinds ofproperty that prime matter has, or perhaps two different ways in whichit has properties. There are its essential properties, which definethe kind of entity that it is, and which it has permanently, and thenthere are its accidental properties, which it gains and loses as itunderlies different sorts of thing. A worry about this solution is, ifone can distinguish between the prime matter and its essentialproperties, this might suggest that there is a need for a furtherentity to act as the underlying thing for those properties, and thenthis further entity would need to have its own nature, and somethingto underlie that nature, and so on. It seems best to try to avoid suchan infinite regress by insisting that prime matter can underlie itsown essential properties, without being a compound of those propertiesand some further matter. (Oderberg 2007, 2014, 2023, and Brower 2014argue that prime matter is logically coherent and compatible withmodern science; for an opposing view, see Koslicki 2018, ch. 2.)

3. The principle of individuation

Another reason that some scholars have thought that Aristotle needssomething like prime matter is to serve as a so-called“principle of individuation”. While the predominant viewhas been that this role is reserved for matter, other scholars havemaintained either that Aristotle means it to be form, or that he doesnot see the need for a principle of individuation at all. Some of thiscontroversy seems to have resulted from a failure to be clear aboutwhat a principle of individuation is, or what problem it is supposedto solve.

To see why this is so, one may focus on a controversy aboutindividuation which Popper sought to dissolve, by pointing out that itderived from a false opposition. This was a controversy begotten by adisagreement between Anscombe and Lukasiewicz regarding the principleof individuation in Aristotle (see Anscombe et al. 1953). Popperpoints out that their disagreement is only apparent, due to the factthat they are answering different questions: Lukasiewicz insists thatform should be counted as the “source of individuality”because it explains how a thing with many parts is a single individualand not a plurality, it accounts for the unity of individuals. He hasin mind questions like “How do all these bricks constitute asingle house?” or “What makes this collection of flesh andbones Socrates?”, and here Aristotle does indeed appear to makeuse of form. On the other hand, Anscombe says that it is matter whichmakes an individual the individual it is, numerically distinct fromother individuals of the same (and other) species. Yet this is anissue about numerical distinctness rather than unity. It is perfectlyconsistent to say that Socrates is one man because of his form, whichunifies his matter into a single whole, and he is a numericallydistinct individual from Callias because his matter is numericallydistinct from Callias’ matter.

It has become conventional to call an answer to Lukasiewicz’sproblem a principle of unity, and an answer to Anscombe’sproblem a principle of individuation. The traditional view has beenthat individuation is a metaphysical issue: what is it that makes oneindividual different from another (of the same kind)? However, somescholars have argued that Aristotle at no point addresses this issue,but is instead concerned with the epistemological question of how wetell one individual from another (see Charlton 1972).

It is worth considering why one might think that the metaphysicalissue is not worth pursuing. The obvious reason is if one thought thatthere was no answer to the question “what makes this individualnumerically distinct from that one?”—that nothingmakes them distinct, they just are. An advocate of this viewmight point out that even if we accept that matter is what makes thisindividual distinct from that one, we still have no answer to thequestion “what makes this portion of matter numerically distinctfrom that one?”. There will always be certain of these numericaldistinctness facts that remain unexplained on any theory. But ifexplanation has to stop somewhere, why not stop at the beginning? Whynot just say that it is a bare fact that Socrates is numericallydistinct from Callias, and leave matter out of it?

One might think that one could respond to this argument by insistingthat there is an answer to the question what makes Socrates’matter numerically distinct from Callias’ matter: it is thematter itself. If matter can explain the distinctness of individualsubstances, why should it not also explain its own distinctness fromother matter? Whether or not this move is legitimate will depend onwhich facts are and which facts are not in need of explanation but maycorrectly be assumed to be primitive. The problem is that “thismatter is distinct from that matter because it is this matter”seems to be a very similar sort of explanation to “Socrates isdistinct from Callias because he is Socrates”—both arecases ofx explaining its own distinctness fromy.Either both should count as adequate explanations or neither should.But the advocate of matter as principle of individuation adopted thisview precisely because she found this sort of explanationunsatisfactory, or not an explanation at all. Therefore this responsedoes not seem to be open to her.

It seems that those who are committed to there being something whichaccounts for the numerical distinctness of individuals must say thatthere is nothing that accounts for the numerical distinctness of thedistinctness-makers. The only alternative would be to introduce somefurther thing to account fortheir distinctness, andso on; but this results in an infinite regress, which, as well asbeing ontologically bloated, appears to be vicious, since we can nevergrasp the full account of what makes Socrates and Callias distinct.Both sides agree that explanation must stop somewhere, but they differover where it is appropriate to stop: is it a basic, inexplicable factthat Socrates is numerically distinct from Callias, or that theirmatter is distinct? (See Markosian 2008, §8, for a contemporarydiscussion of this question.) At any rate, even if it is difficult toprove that there is an important metaphysical question here, thetraditional interpretation of Aristotle is that he thinks thereis.

There are two main texts which have been thought to show Aristotleadvancing the view that matter is the principle of individuation:Metaphysics v 6, 1016b31–2, and vii 8, 1034a5–8.In the first of these, we are told:

Moreover, some things are one in number, some in form, some in genus,some by analogy; in number those whose matter is one…

According to the traditional interpretation, here we have the claimthatx andy are numerically identical (or“one in number”) if, and only if, they have the samematter (or the matter ofx is “one” with thematter ofy). An alternative reading takes this passage to beabout unity rather than individuation: Aristotle would be saying thatx is numerically one if and only ifx’s matteris one, where a thing’s matter being “one” meansthat it is one continuous piece (of bone, for example).

The second important passage for detecting Aristotle’s viewsabout individuation comes at vii 8, 1034a5–8:

And when we have the whole, a form of such a kind in this flesh and inthese bones, this is Callias or Socrates; and they are different invirtue of their matter (for that is different), but the same in form,for their form is indivisible.

According to the traditional interpretation, these lines are sayingthat Socrates and Callias are numerically distinct because of theirmatter, not their form, and on the face of it this is the clearestexample of Aristotle affirming that matter is the principle ofindividuation. We can adopt an alternative reading, however, if wesuppose that “different” means not numerically distinct,but qualitatively different. In that case, the passage could be makingan epistemological claim about how we discern Socrates and Callias:suppose Callias is pale and Socrates dark; they are different, but notdifferent in form; they differ because of their matter, since pallorand darkness primarily qualify their skin, i.e., part of theirbody.

There is a difficulty for the idea that matter can act as theprinciple of individuation, which arises out of the following problemthat can be raised for Aristotle’s hylomorphism (see Fine 1994).It seems that two substances, e.g., Socrates and Callias, may havenumerically the same matter at different times; that it is possible(however unlikely) for all and only the particular elements that nowcompose Socrates to end up composing Callias at some later date. Insuch a case, Socrates and Callias would have the same matter, albeitat different times. Moreover, both being human beings, they would havethe same form. But they themselves are compounds of matter and form,so if their matter and form are numerically the same, they mustthemselves be numerically the same.

Put schematically, the argument looks like this:

1. It is possible that Socrates and Callias be composed ofnumerically the same matter (albeit at different times).
2. Socrates and Callias have the same form.
3. Socrates and Callias are compounds of matter and form.
4. Therefore, it is possible that Socrates and Callias arenumerically the same.

Of course two different people cannot be numerically the same. So, ifthe argument is valid, at least one of its premises must be false.

One possible rejoinder to this argument is that it turns on anequivocation in the meaning of “matter”. As we have seen,for Aristotle matter comes in different levels. In the situationenvisaged Socrates and Callias would have the same remote or low-levelmatter (the same elements) but they might still have differentproximate matter, since the proximate matter of a human being is hisbody. Since a substance is a compound of a substantial form and someproximate matter, we are not entitled to conclude thatSocrates and Callias are the same. Although this may be an effectiveway of dealing with the initial problem, it can be restated so as toavoid this objection that the argument equivocates on“matter”. Each level of matter is a compound of the matterat the level immediately below it and a form. If the proximate matterof two things is to be different, despite their lower-level matterbeing the same, the reason must be that the forms of the proximatematters are different. We can redescribe the situation so that notonly are Socrates’ and Callias’ forms the same, but theforms of their bodies are also the same, and the forms of the matterof their bodies, and so on all the way down. Although it is unclearwhat in general is required for the matter of two things of the sameform to have the same form, e.g., for Socrates’ andCallias’ bodies to have the same form, it seems reasonable tosuppose that it is sufficient for two things to have the same formthat they be qualitatively the same. So we can ensure thatSocrates’ and Callias’ matters have the same form, if wesuppose that they are qualitatively the same. One might insist that notwo things are qualitatively the same, but there is little reason tothink that Aristotle is committed to Leibniz’s doctrine of theidentity of indiscernibles. What is more, although strict qualitativeidentity, i.e., having all the same non-relational and relationalproperties, may require demanding metaphysical assumptions such as aneternally cyclic universe, probably all that is required is that therebe norelevant qualitative difference between Socrates andCallias, where “relevant” means such as to result in themor their matter having different forms. While one might insist thattwo things must be qualitatively the same to have the same form, thisalso does not seem to be Aristotle’s view. So if we tailor ourexample to this requirement, we can thwart the charge of equivocation.The argument then is valid, so we must choose one of its premises toreject.

One might try to reject the first premise of the argument, on thegrounds that a person’s matter is essential to them. We haveseen that Aristotle plausibly does believe this about a person’sproximate matter—their body—since a dead body isonly homonymously a “body”. Nevertheless, he is committedto their more remote matter—the elements that make them up, forinstance—being capable of existing independently of them. Heneeds there to be something to underlie the change whereby a substancecomes into or goes out of existence, to make it consistent with hisaccount of change in general inPhysics i 7. There seems tobe no reason to deny that, when a tree, for instance, dies, the earth,air, fire and water that constituted it still exist in the dead stump.But, if so, there seems no reason to think they could not leave thestump, and end up becoming the matter of some new tree. This is allthat is needed for the problem to arise. Prime matter, if it exists,will not help: if the elements are allowed to escape the substancesthat they underlie, it seems that the prime matter that underliesthem should also be capable of doing so. It is supposed to becapable of underlyinganything; so insisting that it isconfined to being the prime matter of a particular sort of thing makesno sense.

A more promising option is to reject the second premise of theargument, that co-specific or relevantly similar things like Socratesand Callias must have a common form. This one might reject if one werea believer in particular forms. The question of whetherAristotle’s forms are particular or universal has garnered ahuge amount of scholarly attention (those in favour of particularforms include Sellars 1957, Frede 1978, and Irwin 1988; those infavour of universal forms include Albritton 1957, Lewis 1991, Loux1991 and Peramatzis 2011). If Aristotle believed in universal forms,he could have constructed particular forms out of some kind of indexedversion of the universal (e.g., an ordered pair of the universal formand the thing which had it); but that would make the identity of theparticular form dependent on that of the substance that had it. Sinceit is the substance’s form which is acting as principle ofindividuation, if the common form premise is rejected, particularforms cannot be individuated by the substances that have them, on painof circularity: what makes Socrates different from Callias is thatthey have different forms; and what makes their forms different isthat one belongs to Socrates, the other to Callias. To play this role,particular forms would have to be defined independently of the thingsthat have them. It would be a particular form which combines with athing’s matter to make it the thing that it is. Some scholarsfind this conception of particular forms problematic (see Fine 1994,19, for this attitude; on the other hand, Koslicki 2018, ch. 3, and2021, 108, endorses particular forms in her neo-Aristotelianhylomorphism to address the puzzle outlined in this section).

A final reaction to the argument would be to reject the third premise,the idea that anything enmattered is a compound of its matter and format a given time. Certainly the most straightforward way ofunderstanding hylomorphism is that the compound is compounded of thething’s matter and form at a particular time, and the relationbetween the compound and the thing is identity. This way ofunderstanding composition is not only problematic because it leads tothe problem currently under discussion: assuming that things canchange their matter, we might well also wonder (a) how just one of thematters, which it has at a particular time, can yield the whole thing,and (b) how different matters at different times can yield the samething. An alternative way to understand compounding would be to saythat a thing is the compound of its form and all the various mattersthat it has at different times: \(X = F(m_1, m_2, \ldots m_n)\), where\(m_1\ldots m_n\) are \(X\)’s proximate matters in order oftemporal occurrence. This would solve worries (a) and (b) above, sincenow all the different matter-slices are incorporated into the oneobject. It does not obviously help with the problem at hand, however,since, if it is possible for Socrates and Callias to have the samematter at a time, there seems to be no barrier to them having exactlythe same sequence of matter-slices throughout their lives (providedthat they are not born at the same time, and live to exactly the sameage).

Finally, one could relativize the concept of a compound to a time:enmattered objects are absolutely identical to compounds, but acompound is not absolutely a compound of matter and form, but onlyrelative to a particular time. \(X = F_t(m)\), wherem is theproximate matter ofX att; or, combining this ideawith the previous one, \(X = F_t(m_1\ldots m_n)\), where t is theperiod of time for whichX exists, and \(m_1\ldots m_n\) areits matters in order of occurrence. This solution does deal with theproblem directly, since Socrates and Callias can have the same formand matter, and yet be different compounds because the times aredifferent. There may also be a modal version of the puzzle: Socratesis such that his matter and form could be identical with those ofCallias at a certain time. This puzzle might be solved by alsorelativizing compounds to worlds.

There is an exegetical problem with ascribing this final way ofunderstanding composition to Aristotle, and that is that it apparentlyconflicts with the view that he expresses inMetaphysics viii6, 1045a7–10, and vii 17, 1041a26, that a form is what unifies acompound. The problem is how to understand the role of the time in theunification of the compound by the form: it cannot be just anotherelement to be unified, for the time at which the matter exists doesnot figure as a part of the resulting unity. If we try to make theform unify a given portion of matter into many different things,depending on what time the unifying takes place at, we also run intothe difficulty that such a process no longer seems worthy of the title“unification”, since the result is many objects, not justone. Indeed we can reformulate the problem without mentioningcomposition at all: if a common form must unify common matter into oneand the same thing, and Socrates and Callias have the same form andthe same matter, they are one and the same. Since Aristotle (and manyneo-Aristotelians) would surely be unwilling to give up the unifyingrole of form, this does not look like a viable solution.

We have seen that there are some textual reasons to think Aristotlemakes matter his principle of individuation; but in fact particularforms are better suited to play this role. We need to distinguishbetween two different questions, one about unification, the otherabout individuation: (i) what makes this giraffe (or thisgiraffe-matter) one and the same giraffe (over time)? (ii) what makesthis giraffe distinct from that one? The first question seems to bethe one which Aristotle addresses inMetaphysics vii 17, anddoes not obviously require an answer that is unique to the giraffe inquestion. Giraffeness in general may well suffice. The answer to thesecond question, however, cannot be the universal species, since it iscommon to both giraffes, nor can it be their matter, since they could(albeit improbably) be composed of the numerically same stuff atdifferent times. It is not so obvious that Aristotle sees the need toaddress the second question, but, if his forms are particular, notuniversal, he is in a good position to do so.

4. Matter-involving forms

As we have seen, Aristotle introduces matter and form as contrastingnotions, distinct causes, which together make up every ordinaryobject. It may come as a surprise, then, to find that he makescomments which suggest that matter and form are more intimatelyintertwined than is obviously required by the manner of theirintroduction. It is worth noting in this regard that he is eager todistance himself from Plato’s theory of Forms, which exist quiteapart from the material world. He does so in part by insisting thathis own forms are somehow enmeshed in matter (Metaphysics vi1 and vii 11, andDe Anima i 1). He also maintains that allnatural forms are like something which is snub, where something issnub only if it is concavity-realized-in-a-nose (Physics ii2; cf.Sophistical Refutations 13 and 31). The purport seemsto be that all natural forms are such that they are themselves somehowmaterial beings, or at least that one must mention matter in theirspecification. Consequently, some scholars have been inclined tosuppose that a thing’s form itself contains a specification ofthe matter which anything with that form has to have (see Balme 1984,Charles 2008, Peramatzis 2011). If so, rather than being contrastedwith matter, forms will be themselves somehow intrinsically material.Other scholars have been disinclined to draw this inference, not leastbecause it seems to result in an unhappy conflation of the separateroles that matter and form are meant to play in Aristotle’smetaphysics (see Frede 1990, Corkum 2013, and Meister 2020).

The passage in theMetaphysics where Aristotle most obviouslyaddresses this question is vii 11. He begins the chapter by asking“what sorts of thing are parts of the form, and which are not,but are parts of the compound” (1036a26–7). He firstdiscusses the case of things which are realized in multiple differentsorts of matter: a circle may be realized in bronze or stone; so it isclear that its matter, bronze or stone, is not part of the form of thecircle, since it is separate from them (1036a33–4). We are thentold that, in the case of things which are not seen to be separate,nothing prevents the same considerations from applying to them,“even if all the circles that had been seen were bronze”(1036b1).

Having considered the case of circles, Aristotle moves on to considerthe form of a man, and to ask of flesh and bones, “Are these tooparts of the form and definition?” (1036b5). Some interpretersunderstand the next sentence to contain Aristotle’s answer:

In truth no, they are the matter; but, because ‹theform› is not also in other ‹sorts of matter›, weare unable to separate them. (1036b5–7)

Rendered thus, the text suggests that, as in the circle case, fleshand bones are not part of the form of man. However, other editors,especially those friendly to matter-involving forms, print thissentence as a question, so that it reads

Or are they rather matter; but because ‹the form› is notalso in other ‹sorts of matter›, we are unable toseparate them?

This second way of understanding the sentence, though it does notrequire it, leaves open the possibility that Aristotle’s answerwill be that, unlike in the circle case, flesh and bones are indeedpart of the form of a man. Since punctuation marks are a laterinvention, it is impossible to be certain which reading Aristotleintended. The sentence, as it stands, is inconclusive.

We might hope that Aristotle’s view about whether flesh andbones are part of the form of man will become clearer later in thechapter. Unfortunately, the relevant passage is also open to multipleinterpretations. The chapter goes on to describe how

some people are in doubt even in the case of the circle and thetriangle, on the grounds that it is not right to define them in termsof lines and continuity, but that these too should all be spoken of inthe same way as flesh and bones of man and bronze and stone of statue.(1036b8–12)

Presumably these thinkers object to lines and continuity being partsof the definitions of circle and triangle on the grounds that they arematter, comparing them to other sorts of matter that are obviouslyinadmissible in definitions. Aristotle criticizes this line ofthought, which suggests that maybe he does think that certain sorts ofmatter or at least matter-like concepts are admissible in definitions.However, the fact that he groups flesh and bones with bronze and stoneas the sort of matter that is obviously inadmissible suggests that hedoes not think that they are parts of the form of man.

The impression so far is seemingly contradicted a bit later, when weare told:

And therefore to reduce everything in this way and to take away thematter is futile: for surely some things are this ‹form›in this ‹matter› or these things is this state; and thecomparison in the case of animal, which Socrates the Younger used tomake, is not a good one; for it leads away from the truth, and makesone think that it is possible for man to exist without his parts, asthe circle can without bronze. (1036b22–8)

Here Aristotle would seem to be referring back to the earliercomparison between the flesh and bones of a man and the bronze orstone of a statue at 1036b11, and claiming that the comparisonmisleadingly suggests that flesh and bones are not part of the form ofa man, when in fact they are.

That anyway is how those in favour of matter-involving forms take thispassage, but there is another possible reading. Instead of failing torealize that human beings, unlike circles, are essentially realized inflesh and bones, and as such these must be included in their form,Socrates the Younger’s mistake might have been his payinginsufficient attention to the fact that circles, being mathematicalobjects, need not be instantiated in any specific kind of matter atall, whereas human beings always are. If this is the mistake thatAristotle is identifying, this passage would not support any sort ofmatter-involving forms, but only the view that natural forms, like theform of a man, are always instantiated in matter of certain sorts.Even if the forms were necessarily so instantiated, this would notrequire that the matter be included in the specification of thething’s form.

There are other texts, which have been used to argue directly for theview that Aristotle embraces matter-involving forms:De Animai 1, where Aristotle describes anger as desire for retaliationmanifested in boiling of the blood around the heart; orPhysics ii 2, where he says that natural forms are analogousto snubness, i.e., concavity realized in a nose. Defenders of pureforms can attempt to deal with these passages by distinguishingbetween a pure form, and a broader “definition”(logos,horos,horismos) which brings inother causes (see Corkum 2013, and Meister 2020, who distinguishesbetween a pure, metaphysical definition and a looser physicalone).

As well as purely textual arguments, several more philosophicalmotivations have been proffered in favour of matter-involving forms.One such argument relies on the fact that natural things, unlikemathematical ones, are subject to change. Only things with matter arecapable of change, and, if natural forms are to account for thecharacteristic changes undergone by natural compounds, the claim isthat they must themselves be matter-involving. For example, theproperty of falling downwards when unsupported is one had by all humanbeings. Aristotle would explain this propensity as being due to theirbeing made of a preponderance of the heavier elements, earth andwater. If the form of a human being is to account for this fact,plausibly it will have to make mention of the material constitution ofhuman beings that results in this sort of characteristicbehaviour.

In assessing this argument, a lot seems to depend on how extensive anexplanatory role can be assigned to hypothetical necessity (cf.Physics ii 9). All human beings have a tendency to fall,necessarily, at least in a world with laws of physics like ours.However, it is not so clear whether this characteristic sort of changeis one which must be explained by the form or essence of a humanbeing, as opposed to his matter. After all, there are lots of othersorts of thing, both living and inanimate, which share this particularcharacteristic. Supposing there was a characteristic sort of changepeculiar to all and only human beings, even then it is not obvious (a)that this fact has to be explained by the essence of a human being,and (b) that its explanation will require the essence to bematter-involving. To be sure, we would like some explanation of whythis sort of change is peculiar to this sort of creature, but it mightsimply be a fact about the world that anything with an essence of thissort has to change in this sort of way, without that change beingsomething that is specified within the essence itself.

In this connection it is important to notice that Aristotle recognizesthe existence ofidia, that is of properties that apply toall and only instances of a given species, which an instance of thatspecies has necessarily, but which are not part of its essence: e.g.,all and only human beings are capable of laughter (cf.Categories 5, 3a21, 4a10;Topics i 5,102a18–30, and v 5, 134a5–135b6). The essence of a humanbeing is rationality, and the fact that we all (apparently) have asense of humour follows from the essence together with how the worldis. Many characteristic changes of organisms may be best explained ina similar way: all ducks waddle, but waddling is not part of theirfunction. Rather anything that fulfils the functional requirements ofa duck must (in a world like ours) walk inelegantly.

The question of whether or not Aristotelian forms are“essentially matter-involving” is further complicated bysome unclarity about what this description precisely amounts to. Inparticular, it is unclear whether it is supposed to be a thing’sform, which is also its essence, which is matter-involving, or theessence of the form (or both). Aristotle identifies a thing’sform with its essence atMetaphysics vii 7, 1032b1–2:“by form I mean the essence of each thing and‹its› primary substance”. (He makes the sameidentity claim at vii 10, 1035b32, cf. also viii 4, 1044a36.) Withthis in mind, we can divide the possible views about matter-involvingforms into the following four positions, with ascending degrees ofmatter-involvement:

1. Pure forms: natural compounds (and their forms) have forms oressences that are not matter-involving.
2. Compounds have forms or essences that involve matter, i.e., matteris part of the compound’s essence or form. The form that is partof the compound’s form, however, itself has afurtherform or essence that is not matter-involving.
3. As in (2), compounds have forms or essences that involve matter;but forms themselves have no essences or forms.
4. As in (2) and (3), compounds have forms or essences that involvematter; and so do forms, i.e., not only are the forms or essences ofcompounds themselves in some sense compounds of matter and form, as in(2) and (3), but they themselves havefurther essences orforms that are compounds of matter and form.

A serious objection to position (4) is that it apparently leads to avicious infinite regress: if a compound’s essence or form isitself a compound of matter and form, and this second form has anessence or form which is also a hylomorphic compound, etc., everycompound will have an infinite series of essences or forms associatedwith it. Socrates is (essentially) a compound of matter and form, sois his form, so is its form, etc. Note that this regress only appliesif all forms are held to be matter-involving. It does not afflict themore moderate matter-involving position, (2), since it holds that theform of the compound is matter-involving, and hence has both materialand formal parts, but that this second form, the form of the form, ispure, and has itself as a form, e.g., the form of a computer may becomputing functions in certain suitable matter, but the formal part ofthat form (computing functions) would be pure. The regress is notmerely unattractively bloated and otiose. If a full explanation ofwhat something is requires one to list an infinite series of forms,such explanations will not be viable for finite beings like us.

A different way to avoid the regress which plagues (4) would be todeny the assumption that anything that is matter-involving must be acompound of matter and form. Form is matter-involving, but that is notto say that it has its own form or essence and its own matter. Formand matter are introduced to explain certain facts about ordinaryobjects of perception, such as this man or this horse. Once thosefacts have been accounted for, there is no need to look for the sameexplanations of the theoretical entities which have been introduced toprovide the original explanation. This way out of the regress involvesdenying that forms have essences, i.e., it reverts to position (3).This position faces a number of textual obstacles. For instance, atthe beginning ofDe Anima i 1, Aristotle announces that“our aim is to grasp and understand [the soul’s] natureand essence, and secondly its properties” (402a7–8). InMetaphysics vii 11, he refers to the account (logos)of the essence (1037a22–3), and claims that “the accountof the soul is [the account] of the man” (1037a28–9) (cf.alsoPhysics ii 2, 194a13). For these textual reasons itwould be preferable for a proponent of (3) to be able to say thatforms do have essences or definitions in a sense, but they areidentical with these (as snubness = concavity in a nose). Theiressences are not some further thing, distinct from them.

The difficulty with this is that it is not clear that the defender of(3) can claim that forms have definitions of any sort and stillmaintain a doctrine that is distinct from both (2), on the one hand,and (4) on the other. Given that forms are definitions, they must havea structure that approximates to that of a linguistic entity. Whateverelse one says about them then, it seems clear that they must bedivisible (in thought) into component parts, as complex predicates aredivisible into words. We may ask of these component parts whether ornot they are matter-involving, i.e., the question which the proponentof (3) answers in the affirmative with respect to the form or essenceof the compound—does it have parts which correspond to materialterms like “flesh” or “hand” or“matter”? If some parts of the form’s definition arematter-involving, and others are not, this seems to make thedefinition in some sense a compound of material and formal parts. Wecan then identify the formal parts, and ask if there is a definitionof them, and, if the answer is “yes, a matter-involvingone”, we are stuck once again with the regress which afflicted(4). On the other hand, if no part of the form’s definition ismatter-involving, the proponent of (3) must hold that, while compoundshave essences which are matter-involving, these essences havedefinitions which are not, and this seems to make his view intolerablysimilar to (2).

It might seem as though it does not make much difference whetherAristotle subscribes to position (1) or (2). According to (2), everyphysical object has two forms associated with it: a matter-involvingone, which combines with the proximate matter to make up the compound,and a second form or essence of this matter-involving form, which isnot matter-involving. On position (1), a thing has only one form,which is “pure” in the sense that it contains no matter.However, the defender of pure forms must admit that there is also abroader definition of a thing, which does include its matter, as wellas its other causes. Superficially, the only difference seems to bewhether or not this “definition” gets to be classified asa form, and this might appear to be a merely verbal disagreement. Infact, more is at stake here: although, “definition”,“form” and “essence” are often treated asthough they were interchangeable, a definition is strictly-speakingsomething linguistic, whereas an essence or form may have a structurethat corresponds to something linguistic, but it is still a thing inthe world. For example, the essence or form of a human being is asoul. A commitment to two essences or forms per compound substance isan additional metaphysical commitment in a way that a broaderlinguistic definition of a thing that mentions both its form and itsmatter need not be. If important theoretical work cannot be found formatter-involving forms, then, pure forms are the more ontologicallyparsimonious choice.

In any event, one can see that Aristotle’s initial contrastbetween matter and form grows quickly complex once hylomorphism leavesthe domain of change. Although introduced as contrastive notionssuited to explicate change and substantial generation in the absenceof generationex nihilo, any easy contrast between form andmatter turns out to be difficult to sustain once it finds employmentin its further applications. Even so, as Aristotle implies, and asmany of his followers have affirmed, hylomorphism proves no lesselastic than explanatorily powerful across a wide range of explanatoryroles.

Bibliography

Primary Sources

• Apostle, H., 1979,Aristotle’s Metaphysics,Grinell, Iowa: Peripatetic Press.
• Barnes, J., 1984,The Complete Works of Aristotle: the revisedOxford translation, Princeton: Princeton University Press.
• Bostock, D., 1994,Aristotle: Metaphysics Books Ζ andΗ, Oxford: Clarendon Press.
• Charlton, W., 1970,Aristotle Physics Books I and II,translated with introduction, commentary, note on recent work, andrevised bibliography by William Charlton, Oxford: ClarendonPress.
• Hamlyn, D., [1968] 1993,Aristotle De Anima, Books II and III(with passages from Book I), translated with Introduction andNotes by D.W. Hamlyn, with a Report on Recent Work and a RevisedBibliography by Christopher Shields, Oxford: Clarendon Press. (Firstedition, 1968.).
• Joachim, H., 1926,Aristotle on Coming-To-Be and Passing-Away:De generatione et corruptione, Oxford: Clarendon Press.
• Ross, W.D., 1924,Aristotle’s Metaphysics, Oxford:Clarendon Press.

Secondary Sources

• Ackrill, J., 1972/3, “Aristotle’s Definitions ofpsuchê”,Proceedings of the AristotelianSociety, 73: 1991–33. Reprinted in Barnes, Schofield, andSorabji 1979: 65–75.
• –––, 1981,Aristotle the Philosopher,Oxford: Oxford University Press (Chapters 3–4).
• Albritton, R., 1957, “Forms of particular substances inAristotle’sMetaphysics”,Journal ofPhilosophy, 54: 699–708. doi:10.2307/2021934
• Anscombe, G.E.M., J. Lukasiewicz, and K. Popper, 1953,“Symposium: The Principle of Individuation”,Proceedings of the Aristotelian Society (SupplementaryVolume), 27: 69–120.
• Balme, D., 1984, “The Snub”,AncientPhilosophy, 4: 1–8.
• Barnes, L., M. Schofield, and R. Sorabji (eds.), 1979,Articles on Aristotle, 4 vols. Vol. 4: Psychology andAesthetics, London: Duckworth.
• Brower, J. E., 2014,Aquinas’s Ontology of the MaterialWorld: Change, Hylomorphism, and Material Objects, Oxford: OxfordUniversity Press.
• Burnyeat, M., 1992, “Is an Aristotelian theory of mind stillcredible?” in Nussbaum and Rorty 1992: 15–26.
• Caston, V., 2008, “How Hylomorphic Can You Get? Comment onD. Charles, ‘Aristotle’s PsychologicalTheory’”,Proceedings of the Boston Area Colloquium inAncient Philosophy, 24: 30–49.
• Charles, D., 2008, “Aristotle’s PsychologicalTheory”,Proceedings of the Boston Area Colloquium inAncient Philosophy, 24: 1–29.
• –––, 2011, “Some remarks on substance andessence in Aristotle’sMetaphysics Ζ.6”, inMorison and Ierodiakonou 2011: 151–71.
• Charlton, W., 1972, “Aristotle and the Principle ofIndividuation”,Phronesis, 17: 239–49.
• –––, 1983, “Prime Matter: aRejoinder”,Phronesis, 28: 197–211.
• Cohen, S.M., 1984, “Aristotle and Individuation”,Canadian Journal of Philosophy (Supplementary Volume), 10:41–65.
• –––, 1992, “Hylomorphism andFunctionalism”, in Nussbaum and Rorty 1992: 57–73.
• Corkum, P., 2013, “Critical notice for MichailPeramatzis’sPriority in Aristotle’sMetaphysics”,Canadian Journal of Philosophy,43(1): 136–156.
• Devereux, D., and P. Pellegrin (eds.), 1990,Biologie, Logiqueet Metaphysique chez Aristote: Actes du seminaire C.N.R.S.-N.S.F.,Oleron 28 juin-3 juillet 1987.
• Fine, K., 1994, “A Puzzle Concerning Matter and Form”,in Scaltas, Charles, and Gill 1994: 13–40.
• Frede, M., 1978, “Individuals in Aristotle”, in Frede1987: 49–71.
• –––, 1987,Essays in AncientPhilosophy, Minneapolis: University of Minnesota Press.
• –––, 1990, “The Definition of SensibleSubstances inMetaphysics Ζ”, in Devereux andPellegrin 1990: 113–129.
• Gill, M.L., 1989,Aristotle on Substance: the Paradox ofUnity, Princeton: Princeton University Press.
• Graham, D., 1987, “The Paradox of Prime Matter”,Journal of the History of Philosophy, 25: 475–490.
• Irwin, T., 1988,Aristotle’s First Principles,Oxford: Clarendon Press.
• Koslicki, K., 2018,Form, Matter, Substance, Oxford:Oxford University Press.
• –––, 2021, “Form, Matter,Substance”,Chroniques Universitaires 2020–2021,99–119. [Koslicki 2021 available online]
• Lewis, F., 1991,Substance and Predication in Aristotle,Cambridge: Cambridge University Press.
• –––, 2005, “A Nose by Any Other Name:Sameness, Substitution and Essence in Aristotle,MetaphysicsΖ 5”,Oxford Studies in Ancient Philosophy, 28:161–99.
• Loux, M., 1991,Primary Ousia: An Essay on Aristotle’sMetaphysics Ζ and Η, Ithaca: Cornell UniversityPress.
• Malink, M., 2013, “Essence and Being. A Discussion ofMichail Peramatzis,Priority in Aristotle’sMetaphysics”,Oxford Studies in AncientPhilosophy, 45: 341–362.
• Markosian, N., 2008, “Restricted Composition”, inSider, Hawthorne, and Zimmerman 2008: 341–363.
• Meister, S., 2020, “Aristotle on the Purity of Forms inMetaphysics Z.10–11”,Ergo, 7:1–33.
• Morison, B., and K. Ierodiakonou (eds.), 2011,Episteme, etc.:Essays in Honour of Jonathan Barnes, Oxford: Oxford UniversityPress.
• Novotný, D. D. and Novák, L. (eds.), 2014,Neo-Aristotelian Perspectives in Metaphysics, New York:Routledge.
• Oderberg, D. S., 2007,Real Essentialism, New York:Routledge.
• –––, 2014, “Is Form Structure?”, inNovotný and Novák 2014: 164–180.
• –––, 2023, “Is Prime MatterEnergy?”,Australasian Journal of Philosophy, 101(3):534–50.
• Nussbaum, M., and R. Rorty (eds.), 1992,Essays inAristotle’s De Anima, Oxford: Clarendon Press.
• Robinson, H., 1974, “Prime Matter in Aristotle”,Phronesis, 19: 168–88.
• Peramatzis, M., 2011,Priority in Aristotle’sMetaphysics, Oxford: Oxford University Press.
• Scaltas, T., D. Charles, and M.L. Gill (eds.), 1994,Unity,Identity and Explanation in Aristotle’s Metaphysics,Oxford: Clarendon Press.
• Sellars, W.S., 1957, “Substance and form inAristotle”,Journal of Philosophy, 54:688–99.
• Shields, C., 1988, “Soul and Body in Aristotle”,Oxford Studies in Ancient Philosophy, 6: 103–137.
• –––, 1993, “The Homonymy of the Body inAristotle”,Archive für Geschichte derPhilosophie, 75: 1–30.
• –––, 2007,Aristotle, New York:Routledge (Chapter 2).
• Sider, T., 1993, “Van Inwagen and the Possibility ofGunk”,Analysis, 53: 285–9.
• –––, 2006, “Bare Particulars”,Philosophical Perspectives, 20: 387–97.
• Sider, T., J. Hawthorne and D.W. Zimmerman (eds.), 2008,Contemporary Debates in Metaphysics, Oxford: Blackwell.
• Sorabji, R., 1974, “Body and Soul in Aristotle”,Philosophy, 49: 63–89.
• White, N., 1986, “Identity, Modal Individuation, and Matterin Aristotle”,Midwest Studies in Philosophy, 11:475–494.
• Whiting, J., 1986, “Form and Individuation inAristotle”,History of Philosophy Quarterly, 3:359–377.

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