The first major work in the history of philosophy to bear the title“Metaphysics” was the treatise by Aristotle that we havecome to know by that name. But Aristotle himself did not use thattitle or even describe his field of study as‘metaphysics’; the name was evidently coined by the firstcentury C.E. editor who assembled the treatise we know asAristotle’sMetaphysics out of various smallerselections of Aristotle’s works. The title‘metaphysics’—literally, ‘after thePhysics’—very likely indicated the place thetopics discussed therein were intended to occupy in the philosophicalcurriculum. They were to be studied after the treatises dealing withnature (ta phusika). In this entry, we discuss the ideas thatare developed in Aristotle’s treatise.

References in the text to the books of Aristotle’sMetaphysics are given by Greek letter. In order (with thecorresponding Roman numeral given in parentheses) these are: Α(I), α (II), Β (III), Γ (IV), Δ (V), Ε(VI), Ζ (VII), Η (VIII), Θ (IX), I (X), Κ (XI),Λ (XII), Μ (XIII), Ν (XIV). Translations are taken fromReeve (2016).

• 1. The Subject Matter of Aristotle’s Metaphysics
• 2. The Categories
• 3. The Role of Substance in the Study of Being Qua Being
• 4. The Fundamental Principles: Axioms
• 5. What is Substance?
• 6. Substance, Matter, and Subject
• 7. Substance and Essence
• 8. Substances as Hylomorphic Compounds
• 9. Substance and Definition
• 10. Substances and Universals
• 11. Substance as Cause of Being
• 12. Actuality and Potentiality
• 13. Unity Reconsidered
• 14. Theology
• 15. Glossary of Aristotelian Terminology
• Bibliography
• Academic Tools
• Other Internet Resources
• Related Entries

1. The Subject Matter of Aristotle’s Metaphysics

Aristotle himself described his subject matter in a variety of ways:as ‘first philosophy’, or ‘the study of being quabeing’, or ‘wisdom’, or ‘theology’. Acomment on these descriptions will help to clarify Aristotle’stopic.

InMetaphysics Α.1, Aristotle says that “everyonetakes what is called ‘wisdom’ (sophia) to beconcerned with the primary causes (aitia) and thestarting-points (or principles,archai)”(981^b28), and it is these causes and principles that heproposes to study in this work. It is his customary practice to beginan inquiry by reviewing the opinions previously held by others, andthat is what he does here, as Book Α continues with a history ofthe thought of his predecessors about causes and principles.

These causes and principles are clearly the subject matter of what hecalls ‘first philosophy’. But this does not mean thebranch of philosophy that should be studied first. Rather, it concernsissues that are in some sense the most fundamental or at the highestlevel of generality. Aristotle distinguished between things that are“better known to us” and things that are “betterknown in themselves,”^[1] and maintained that we should begin our study of a given topic withthings better known to us and arrive ultimately at an understanding ofthings better known in themselves. The principles studied by‘first philosophy’ may seem very general and abstract, butthey are, according to Aristotle, better known in themselves, howeverremote they may seem from the world of ordinary experience. Still,since they are to be studied only by one who has already studiednature (which is the subject matter of thePhysics), they arequite appropriately described as coming “after thePhysics.”

Aristotle’s description ‘the study of being quabeing’ is frequently and easily misunderstood, for it seems tosuggest that there is a single (albeit special) subjectmatter—being qua being—that is under investigation. ButAristotle’s description does not involve two things—(1) astudy and (2) a subject matter (being qua being)—for he did notthink that there is any such subject matter as ‘being quabeing’. Rather, his description involves three things: (1) astudy, (2) a subject matter (being), and (3) a manner in which thesubject matter is studied (qua being).

Aristotle’s Greek word that has been Latinized as‘qua’ means roughly ‘in so far as’ or‘under the aspect’. A study ofx quay,then, is a study ofx that concerns itself solely with they aspect ofx. So Aristotle’s study does notconcern some recondite subject matter known as ‘being quabeing’. Rather it is a study of being, or better, ofbeings—of things that can be said to be—that studies themin a particular way: as beings, in so far as they are beings.

Of course, first philosophy is not the only field of inquiry to studybeings. Natural science and mathematics also study beings, but indifferent ways, under different aspects. The natural scientist studiesthem as things that are subject to the laws of nature, as things thatmove and undergo change. That is, the natural scientist studies thingsqua movable (i.e., in so far as they are subject to change). Themathematician studies things qua countable and measurable. Themetaphysician, on the other hand, studies them in a more general andabstract way—qua beings. So first philosophy studies the causesand principles of beings qua beings. In Γ.2, Aristotle adds thatfor this reason it studies the causes and principles of substances(ousiai). We will explain this connection in Section 3below.

In Book Ε, Aristotle adds another description to the study ofthe causes and principles of beings qua beings. Whereas naturalscience studies objects that are material and subject to change, andmathematics studies objects that although not subject to change arenevertheless not separate from (i.e., independent of) matter, there isstill room for a science that studies things (if indeed there are any)that are eternal, not subject to change, and independent of matter.Such a science, he says, is theology, and this is the“first” and “highest” science.Aristotle’s identification of theology, so conceived, with thestudy of being qua being has proved challenging to his interpreters.We discuss this identification inSection 14 below.

Finally, we may note that in Book Β, Aristotle delineates hissubject matter in a different way, by listing the problems orperplexities (aporiai) he hopes to deal with. Characteristicof these perplexities, he says, is that they tie our thinking up inknots. They include the following, among others: Are sensiblesubstances the only ones that exist, or are there others besides them?Is it kinds or individuals that are the elements and principles ofthings? And if it is kinds, which ones: the most generic or the mostspecific? Is there a cause apart from matter? Is there anything apartfrom material compounds? Are the principles limited, either in numberor in kind? Are the principles of perishable things themselvesperishable? Are the principles universal or particular, and do theyexist potentially or actually? Are mathematical objects (numbers,lines, figures, points) substances? If they are, are they separatefrom or do they always belong to sensible things? And (“thehardest and most perplexing of all,” Aristotle says) are unityand being the substance of things, or are they attributes of someother subject? In the remainder of Book Β, Aristotle presentsarguments on both sides of each of these issues, and in subsequentbooks he takes up many of them again. But it is not always clearprecisely how he resolves them, and it is possible that Aristotle didnot think that theMetaphysics contains definitive solutionsto all of these perplexities.

2. The Categories

To understand the problems and project of Aristotle’sMetaphysics, it is best to begin with one of his earlierworks, theCategories. Although placed by long traditionamong his logical works (see the discussion in the entry onAristotle’s logic), due to its analysis of the terms that make up the propositions out ofwhich deductive inferences are constructed, theCategoriesbegins with a strikingly general and exhaustive account of the thingsthere are (ta onta)—beings. According to this account,beings can be divided into ten distinct categories. (AlthoughAristotle never says so, it is tempting to suppose that thesecategories are mutually exclusive and jointly exhaustive of the thingsthere are.) They include substance, quality, quantity, and relation,among others. Of these categories of beings, it is the first,substance (ousia), to which Aristotle gives a privilegedposition.

Substances are unique in being independent things; the items in theother categories all depend somehow on substances. That is, qualitiesare the qualities of substances; quantities are the amounts and sizesthat substances come in; relations are the way substances stand to oneanother. These various non-substances all owe their existence tosubstances—each of them, as Aristotle puts it, exists only‘in’ a subject. That is, each non-substance “is insomething, not as a part, and cannot exist separately from what it isin” (Cat. 1^a25). Indeed, it becomes clearthat substances are the subjects that these ontologically dependentnon-substances are ‘in’.

Each member of a non-substance category thus stands in this inherencerelation (as it is frequently called) to some substance orother—color is always found in bodies, knowledge in the soul.Neither whiteness nor a piece of grammatical knowledge, for example,is capable of existing on its own. Each requires for its existencethat there be some substance in which it inheres.

In addition to this fundamental inherence relation across categories,Aristotle also points out another fundamental relation that obtainsbetween items within a single category. He describes this as therelation of “being said of a subject,” and his examplesmake clear that it is the relation of a more general to a less generalthing within a single category. Thus, man is ‘said of’ aparticular man, and animal is ‘said of’ man, andtherefore, as Aristotle points out, animal is ‘said of’the particular man also. The ‘said of’ relation, that isto say, is transitive (cf. 1^b10). So the genus (e.g.,animal) is ‘said of’ the species (e.g., man) and bothgenus and species are ‘said of’ the particular. The sameholds in non-substance categories. In the category of quality, forexample, the genus (color) is ‘said of’ the species(white) and both genus and species are ‘said of’ theparticular white. There has been considerable scholarly dispute aboutthese particulars in nonsubstance categories. For more detail, see thesupplementary document:

Nonsubstantial Particulars

The language of this contrast (‘in’ a subject vs.‘said of’ a subject) is peculiar to theCategories, but the idea seems to recur in other works as thedistinction between accidental vs. essential predication. Similarly,in works other than theCategories, Aristotle uses the label‘universals’ (ta katholou) for the things thatare “said of many;” things that are not universal he calls‘particulars’ (ta kath’ hekasta). Althoughhe does not use these labels in theCategories, it is notmisleading to say that the doctrine of theCategories is thateach category contains a hierarchy of universals and particulars, witheach universal being ‘said of’ the lower-level universalsand particulars that fall beneath it. Each category thus has thestructure of an upside-down tree.^[2] At the top (or trunk) of the tree are the most generic items in that category^[3] (e.g., in the case of the category of substance, the genus plant andthe genus animal); branching below them are universals at the nexthighest level, and branching below these are found lower levels ofuniversals, and so on, down to the lowest level universals (e.g., suchinfimae species as man and horse); at the lowestlevel—the leaves of the tree—are found the individualsubstances, e.g., this man, that horse, etc.

The individuals in the category of substance play a special role inthis scheme. Aristotle calls them “primary substances”(prôtai ousiai) for without them, as he says, nothingelse would exist. Indeed, Aristotle offers an argument(2^a35–2^b7) to establish the primarysubstances as the fundamental entities in this ontology. Everythingthat is not a primary substance, he points out, stands in one of thetwo relations (inhering ‘in’, or being ‘saidof’) to primary substances. A genus, such as animal, is‘said of’ the species below it and, since they are‘said of’ primary substances, so is the genus (recall thetransitivity of the ‘said of’ relation). Thus, everythingin the category of substance that is not itself a primary substanceis, ultimately, ‘said of’ primary substances. And if therewere no primary substances, there would be no “secondary”substances (species and genera), either. For these secondarysubstances are just the ways in which the primary substances arefundamentally classified within the category of substance. As for themembers of non-substance categories, they too depend for theirexistence on primary substances. A universal in a non-substancecategory, e.g., color, in the category of quality, is ‘in’body, Aristotle tells us, and therefore in individual bodies. Forcolor could not be ‘in’ body, in general, unless it were‘in’ at least some particular bodies. Similarly,particulars in non-substance categories (although there is not generalagreement among scholars about what such particulars might be) cannotexist on their own. E.g., a determinate shade of color, or aparticular and non-shareable bit of that shade, is not capable ofexisting on its own—if it were not ‘in’ at leastsome primary substance, it would not exist. So primary substances arethe basic entities—the basic “things that thereare”—in the world of theCategories.

3. The Role of Substance in the Study of Being Qua Being

TheCategories leads us to expect that the study of being ingeneral (being qua being) will crucially involve the study ofsubstance, and when we turn to theMetaphysics we are notdisappointed. First, inMetaphysics Γ Aristotle arguesin a new way for the ontological priority of substance; and then, inBooks Ζ, Η, and Θ, he wrestles with the problem of whatit is to be a substance. We will begin with Γ’s account ofthe central place of substance in the study of being qua being.

As we noted above, metaphysics (or, first philosophy) is the sciencewhich studies being qua being. In this respect it is unlike thespecialized or departmental sciences, which study only part of being(only some of the things that exist) or study beings only in aspecialized way (e.g., only in so far as they are changeable, ratherthan in so far as they are beings).

But ‘being’, as Aristotle tells us in Γ.2, is“said in many ways”. That is, the verb ‘to be’(einai) has different senses, as do its cognates‘being’ (on) and ‘entities’(onta). So the universal science of being qua being appearsto founder on an equivocation: how can there be a single science ofbeing when the very term ‘being’ is ambiguous?

Consider an analogy. There are dining tables, and there are tidetables. A dining table is a table in the sense of a smooth flat slabfixed on legs; a tide table is a table in the sense of a systematicarrangement of data in rows and columns. But there is not a singlesense of ‘table’ which applies to both the piece offurniture at which I am writing these words and to the small bookletthat lies upon it. Hence it would be foolish to expect that there is asingle science of tables, in general, that would include among itsobjects both dining tables and tide tables. Tables, that is to say, donot constitute a single kind with a single definition, so no singlescience, or field of knowledge, can encompass precisely those thingsthat are correctly called ‘tables’.

If the term ‘being’ were ambiguous in the way that‘table’ is, Aristotle’s science of being qua beingwould be as impossible as a science of tables qua tables. But,Aristotle argues in Γ.2, ‘being’ is not ambiguous inthis way. ‘Being’, he tells us, is ‘said in manyways’ but it is not merely (what he calls)‘homonymous’, i.e., sheerly ambiguous. Rather, the varioussenses of ‘being’ have what he calls a ‘proshen’ ambiguity—they are all related to a singlecentral sense. (The Greek phrase ‘pros hen’ means“in relation to one.”)

Aristotle explains his point by means of some examples that he takesto be analogous to ‘being’. Consider the terms‘healthy’ and ‘medical’. Neither of these hasa single definition that applies uniformly to all cases: not everyhealthy (or medical) thing is healthy (medical) in the same sense of‘healthy’ (‘medical’). There is a range ofthings that can be called ‘healthy’: people, diets,exercise, complexions, etc. Not all of these are healthy in the samesense. Exercise is healthy in the sense of being productive of health;a clear complexion is healthy in the sense of being symptomatic ofhealth; a person is healthy in the sense of having good health.

But notice that these various senses have something in common: areference to one central thing, health, which is actually possessed byonly some of the things that are spoken of as ‘healthy’,namely, healthy organisms, and these are said to be healthy in theprimary sense of the term. Other things are considered healthy only inso far as they are appropriately related to things that are healthy inthis primary sense.

The situation is the same, Aristotle claims, with the term‘being’. It, too, has a primary sense as well as relatedsenses in which it applies to other things because they areappropriately related to things that are called ‘beings’in the primary sense. The beings in the primary sense are substances;the beings in other senses are the qualities, quantities, etc., thatbelong to substances. An animal, e.g., a horse, is a being, and so isa color, e.g, white, a being. But a horse is a being in the primarysense—it is a substance—whereas the color white (aquality) is a being only because it qualifies some substance. Anaccount of the being of anything that is, therefore, will ultimatelyhave to make some reference to substance. Hence, the science of beingqua being will involve an account of the central case ofbeings—substances.

4. The Fundamental Principles: Axioms

Before embarking on this study of substance, however, Aristotle goeson in Book Γ to argue that first philosophy, the most general ofthe sciences, must also address the most fundamentalprinciples—the common axioms—that are used in allreasoning. Thus, first philosophy must also concern itself with theprinciple of non-contradiction (PNC): the principle that “thesame thing cannot at the same time belong and also not belong to thesame thing and in the same respect” (1005^b19). This,Aristotle says, is the most certain of all principles, and it is notjust a hypothesis. It cannot, however, be proved, since it isemployed, implicitly, in all proofs, no matter what the subjectmatter. It is a first principle, and hence is not derived fromanything more basic.

What, then, can the science of first philosophy say about the PNC? Itcannot offer a proof of the PNC, since the PNC is presupposed by anyproof one might offer—any purported proof of the PNC wouldtherefore be circular. Aristotle thus does not attempt to prove thePNC; in the subsequent chapters of Γ he argues, instead, that itis impossible to disbelieve the PNC. Those who would claim to deny thePNC cannot, if they have any beliefs at all, believe that it is false.For one who has a belief must, if he is to express this belief tohimself or to others, say something—he must make an assertion.He must, as Aristotle says, signify something. But the very act ofsignifying something is possible only if the PNC is accepted. Withoutaccepting the PNC, one would have no reason to think that his wordshave any signification at all—they could not mean one thingrather than another. So anyone who makes any assertion has alreadycommitted himself to the PNC. Aristotle thus does not argue that thePNC is a necessary truth (that is, he does not try to prove the PNC);rather, he argues that the PNC is indubitable. (For more on the PNC,see the discussion in the entry onAristotle’s logic)

5. What is Substance?

In the seventeen chapters that make up Book Ζ of theMetaphysics, Aristotle takes up the promised study ofsubstance. He begins by reiterating and refining some of what he saidin Γ: that ‘being’ is said in many ways, and thatthe primary sense of ‘being’ is the sense in whichsubstances are beings. Here, however, he explicitly links thesecondary senses of ‘being’ to the non-substancecategories. The primacy of substance leads Aristotle to say that theage-old question ‘What is being?’ “is just thequestion ‘What is substance?’”(1028^b4).

One might have thought that this question had already been answered intheCategories. There we were given, as examples of primarysubstances, an individual man or horse, and we learned that a primarysubstance is “what is neither in a subject nor said of asubject” (2^a10). This would seem to provide us withboth examples of, and criteria for being, primary substances. But inMetaphysics Ζ, Aristotle does not seem to take eitherthe examples or the criteria for granted.

In Ζ.2 he recounts the various answers that have been given tothe question of which things are substances—bodies (includingplants, animals, the parts of plants and animals, the elements, theheavenly bodies), things more basic than bodies (surfaces, lines, andpoints), imperceptible things (such as Platonic Forms and mathematicalobjects)—and seems to regard them all as viable candidates atthis point. He does not seem to doubt that the clearest examples ofsubstances are perceptible ones, but leaves open the question whetherthere are others as well.

Before answering this question about examples, however, he says thatwe must first answer the question about criteria: what is it to be asubstance (tên ousian prôton ti estin)? Thenegative criterion (“neither in a subject nor said of asubject”) of theCategories tells us only which thingsare substances. But even if we knowthat something is asubstance, we must still say whatmakes it asubstance—what the cause is of its being a substance. This isthe question to which Aristotle next turns. To answer it is toidentify, as Aristotle puts it, the substanceof thatthing.

6. Substance, Matter, and Subject

Ζ.3 begins with a list of four possible candidates for being thesubstance of something: essence, universal, genus, and subject.Presumably, this means that ifx is a substance, then thesubstance ofx might be either (i) the essence ofx,or (ii) some universal predicated ofx, or (iii) a genus thatx belongs to, or (iv) a subject of whichx ispredicated. The first three candidates are taken up in later chapters,and Ζ.3 is devoted to an examination of the fourth candidate: theidea that the substance of something is a subject of which it ispredicated.

A subject, Aristotle tells us, is “that of which the otherthings are said, but which is itself not further said of any otherthing” (1028^b36). This characterization of a subjectis reminiscent of the language of theCategories, which tellsus that a primary substance is not predicated of anything else,whereas other things are predicated of it. Candidate (iv) thus seemsto reiterate theCategories criterion for being a substance.But there are two reasons to be wary of drawing this conclusion.First, whereas the subject criterion of theCategories toldus that substances were the ultimate subjects of predication, thesubject criterion envisaged here is supposed to tell us what thesubstanceof something is. So what it would tell us is thatifx is a substance, then the substance ofx—that which makesx a substance—is asubject thatx is predicated of. Second, as his next commentmakes clear, Aristotle has in mind something other than thisCategories idea. For the subject that he here envisages, hesays, is either matter or form or the compound of matter and form.These are concepts from Aristotle’sPhysics, and noneof them figured in the ontology of theCategories. Toappreciate the issues Aristotle is raising here, we must brieflycompare his treatment of the notion of a subject in thePhysics with that in theCategories.

In theCategories, Aristotle was concerned with subjects ofpredication: what are the things we talk about, and ascribe propertiesto? In thePhysics, his concern is with subjects of change:what is it that bears (at different times) contrary predicates andpersists through a process of change? But there is an obviousconnection between these conceptions of a subject, since a subject ofchange must have one predicate belonging to it at one time that doesnot belong to it at another time. Subjects of change, that is, arealso subjects of predication. (The converse is not true: numbers aresubjects of predication—six is even, seven is prime—butnot of change.)

In theCategories, individual substances (a man, a horse)were treated as fundamental subjects of predication. They were alsounderstood, indirectly, as subjects of change. (“A substance,one and the same in number, can receive contraries. An individual man,for example, being one and the same, becomes now pale and now dark,now hot and now cold, now bad and now good”4^a17–20.) These are changes in which substances move,or alter, or grow. What theCategories did not explore,however, are changes in which substances are generated or destroyed.But the theory of change Aristotle develops in thePhysicsrequires some other subject for changes such as these—a subjectof which substance is predicated—and it identifies matter as thefundamental subject of change (192^a31–32). Change isseen in thePhysics as a process in which matter either takeson or loses form.

The concepts of matter and form, as we noted, are absent from theCategories. Individual substances—this man or thathorse—apart from their accidental characteristics—thequalities, etc., that inhere in them—are viewed in that work asessentially simple, unanalyzable atoms. Although there is metaphysicalstructure to the fact that, e.g.,this horse is white (acertain quality inheres in a certain substance), the fact thatthis is a horse is a kind of brute fact, devoid ofmetaphysical structure. This horse is a primary substance, andhorse, the species to which it belongs, is a secondarysubstance. But there is no predicative complex corresponding to thefact that this is a horse in the way that there is such a complexcorresponding to the fact that this horse is white.

But from the point of view of thePhysics, substantialindividuals are seen as predicative complexes (cf. Matthen 1987b);they are hylomorphic compounds—compounds of matter andform—and the subject criterion looks rather different from thehylomorphic perspective.Metaphysics Ζ.3 examines thesubject criterion from this perspective.

Matter, form, and the compound of matter and form may all beconsidered subjects, Aristotle tells us, (1029^a2–4),but which of them is substance? The subject criterion by itself leadsto the answer that the substance ofx is an entirelyindeterminate matter of whichx is composed(1029^a10). For form is predicated of matter as subject, andone can always analyze a hylomorphic compound into its predicates andthe subject of which they are predicated. And when all predicates havebeen removed (in thought), the subject that remains is nothing at allin its own right—an entity all of whose properties areaccidental to it (1029^a12–27). The resulting subjectis matter from which all form has been expunged. (Traditionalscholarship calls this “prime matter,” but Aristotle doesnot here indicate whether he thinks there actually is such a thing.)So the subject criterion leads to the answer that the substance ofx is the formless matter of which it is ultimatelycomposed.

But Aristotle rejects this answer as impossible (1029^a28),claiming that substance must be “separable”(chôriston) and “this something” (todeti, sometimes translated “some this”), and implyingthat matter fails to meet this requirement. Precisely what therequirement amounts to is a matter of considerable scholarly debate,however. A plausible interpretation runs as follows. Separability hasto do with being able to exist independently (x is separablefromy ifx is capable of existing independently ofy), and being a this something means being a determinateindividual. So a substance must be a determinate individual that iscapable of existing on its own. (One might even hold, although this iscontroversial, that on Aristotle’s account not every “thissomething” is also “separable.” A particular coloror shape might be considered a determinate individual that is notcapable of existing on its own—it is always the color of shapeof some substance or other.) But matter fails to be simultaneouslybothchôriston andtode ti. The matter ofwhich a substance is composed may exist independently of thatsubstance (think of the wood of which a desk is composed, whichexisted before the desk was made and may survive the disassembly ofthe desk), but it is not as such any definite individual—it isjust a quantity of a certain kind of matter. Of course, the matter maybe construed as constituting a definite individual substance (the woodjustis, one might say, the particular desk it composes), butit is in that sense not separable from the form or shape that makes itthat substance (the wood cannot be that particular desk unless it isa desk). So although matter is in a sense separable and in asense a this something, it cannot be both separable and a thissomething. It thus does not qualify as the substance of the thingwhose matter it is.

7. Substance and Essence

Aristotle turns in Ζ.4 to a consideration of the next candidatefor substance: essence. (‘Essence’ is the standard Englishtranslation of Aristotle’s curious phraseto ti êneinai, literally “the what it was to be” for a thing.This phrase so boggled his Roman translators that they coined the wordessentia to render the entire phrase, and it is from thisLatin word that ours derives. Aristotle also sometimes uses theshorter phraseto ti esti, literally “the what itis,” for approximately the same idea.) In hislogical works, Aristotle links the notion of essence to that of definition(horismos)—“a definition is an account(logos) that signifies an essence” (Topics102^a3)—and he links both of these notions to acertain kind ofper se predication (kath’hauto, literally, “in respect of itself,” or“intrinsically”)—“what belongs to a thing inrespect of itself belongs to it in its essence (en tôi tiesti)” for we refer to it “in the account that statesthe essence” (PosteriorAnalytics,73^a34–5). He reiterates these ideas in Ζ.4:“there will be an essence only of those things whoselogos is a definition” (1030^a6), “theessence of each thing is what it is said to be intrinsically”(1029^b14). It is important to remember that for Aristotle,one defines things, not words. The definition of tiger does not tellus the meaning of the word ‘tiger’; it tells us what it isto be a tiger, what a tiger is said to be intrinsically. Thus, thedefinition of tiger states the essence—the “what it is tobe” of a tiger, what is predicated of the tigerperse.

Aristotle’s preliminary answer (Ζ.4) to the question“What is substance?” is that substance is essence, butthere are important qualifications. For, as he points out,“definition (horismos), like ‘what-it-is’(ti esti), is said in many ways too”(1030^a19). That is, items in all the categories aredefinable, so items in all the categories have essences—just asthere is an essence of man, there is also an essence of white and anessence of musical. But, because of thepros hen equivocityof ‘is’, such essences are secondary—“in theprimary (protôs) and unconditional way(haplôs) definition and the essence belong tosubstances” (1030^b4–6). Thus, Ζ.4 tellsus, it is only these primary essences that are substances. Aristotledoes not here work out the details of this “hierarchy ofessences” (Loux, 1991), but it is possible to reconstruct atheory of such a hierarchy on the basis of subsequent developments inBook Ζ.

In Ζ.6, Aristotle goes on to argue that if something is“primary” and “spoken of in respect of itself(kath’ hauto legomenon)” it is one and the sameas its essence. The precise meaning of this claim, as well as thenature and validity of the arguments offered in support of it, arematters of scholarly controversy. But it does seem safe to say thatAristotle thinks that an “accidental unity” such as a paleman is not akath’ hauto legomenon (since pallor is anaccidental characteristic of a man) and so is not the same as itsessence.Pale man, that is to say, does not specify the“what it is” of any primary being, and so cannot be anessence of the primary kind. As Ζ.4 has already told us, essence,in the primary sense, “will belong to things that are species ofa genus and to nothing else” (1030^a11–12).Man is a species, and so there is an essence of man; butpale man is not a species and so, even if there is such athing as the essence of pale man, it is not, at any rate, a primaryessence.

At this point there appears to be a close connection between theessence of a substance and its species (eidos), and thismight tempt one to suppose that Aristotle is identifying the substanceof a thing (since the substance of a thing is its essence) with itsspecies. (A consequence of this idea would be that Aristotle isradically altering his conception of the importance of the species,which in theCategories he called a secondary substance, thatis, a substance only in a secondary sense.) But such an identificationwould be a mistake, for two reasons. First, Aristotle’s point at1030^a11 is not that a species is an essence, but that anessence of the primary kind corresponds to a species (e.g.,man) and not to some more narrowly delineated kind (e.g.,pale man). Second, the word ‘eidos’,which meant ‘species’ in the logical works, has acquired anew meaning in a hylomorphic context, where it means‘form’ (contrasted with ‘matter’) rather than‘species’ (contrasted with ‘genus’). In theconceptual framework ofMetaphysics Ζ, a universal suchasman orhorse—which was called a species anda secondary substance in theCategories—is construed as“not substance but rather a compound of a sort, [consisting] ofthis account and this matter taken universally” (Ζ.10,1035^b29–30). Theeidos that is primarysubstance in Book Ζ is not the species that an individualsubstance belongs to but the form that is predicated of the matter ofwhich it is composed.^[4]

8. Substances as Hylomorphic Compounds

The role of form in this hylomorphic context is the topic ofΖ.7–9. (Although these chapters were almost certainly notoriginally included in Book Ζ—there is no reference tothem, for example, in the summary of Ζ given in Η.1, whichskips directly from Ζ.6 to Ζ.10—they provide a linkbetween substance and form and thus fill what would otherwise be a gapin the argument.) Since individual substances are seen as hylomorphiccompounds, the role of matter and form in their generation must beaccounted for. Whether we are thinking of natural objects, such asplants and animals, or artifacts, such as houses, the requirements forgeneration are the same. We do not produce the matter (to suppose thatwe do leads to an infinite regress) nor do we produce the form (whatcould we make it out of?); rather, we put the form into the matter,and produce the compound (Ζ.8, 1033^a30–b9). Boththe matter and the form must pre-exist (Ζ.9, 1034^b12).But the source of motion in both cases—what Aristotle calls the“moving cause” of the coming to be—is the form.

In production that results from craft (or art,technê),“the form is in the soul” (1032^b23) of thecraftsman. For example, “the craft [of building] is the form [ofthe house]” (1034^a24) and the craft, i.e., the form,is in the understanding, and hence in the soul, of the builder. Thebuilder has in mind the plan or design for a house and he knows how tobuild; he then “enmatters” that plan or design by puttingit into the materials out of which he builds the house. In naturalproduction, the form is found in the parent, where “the begetteris of this same sort as the begotten (not that they are the samething, certainly, nor one in number, but one in form)—forexample, in the case of natural things. For human begets human”(1033^b29–31). But in either case, the form pre-existsand is not produced (1033^b18).

As for what is produced in such hylomorphic productions, it iscorrectly described by the name of its form, not by that of itsmatter. What is produced is a house or a man, not bricks or flesh. Ofcourse, what is made of gold may still be described in terms of itsmaterial components, but we should call it not “gold” but“golden” (1033^a7). For if gold is the matterout of which a statue is made, there was gold present at the start,and so it was not gold that came into being. It was a statue that cameinto being, and although the statue is golden—i.e., made ofgold—it cannot be identified with the gold of which it wasmade.

The essence of such a hylomorphic compound is evidently its form, notits matter. As Aristotle says “by form I mean the essence ofeach thing and the primary substance” (1032^b1), and“by the substance without matter I mean the essence”(1032^b14). It is the form of a substance that makes it thekind of thing that it is, and hence it is form that satisfies thecondition initially required for being thesubstance ofsomething. The substance of a thing is its form.

9. Substance and Definition

In Ζ.10 and 11, Aristotle returns to the consideration of essenceand definition left off in Ζ.6, but now within the hylomorphiccontext developed in Ζ.7–9. The main question thesechapters consider is whether the definition ofx everincludes a reference to the matter ofx. If some definitionsinclude a reference to matter, then the link between essence and formwould seem to be weakened.

Aristotle begins Ζ.10 by endorsing the following principle aboutdefinitions and their parts: “a definition is an account, andevery account has parts, and as the account is to the thing, so thepart of the account is to the part of the thing”(1034^b20–22). That is, ify is a part of adefinable thingx, then the definition ofx willinclude as a part somethingz that corresponds toy.Indeed,z must stand toy in the same relation thatthe definition ofx stands in tox; that is,z is the definition ofy. So, according to thisprinciple, the definition of a thing will include the definitions ofits parts.

In a way, this consequence of the principle seems very plausible,given Aristotle’s idea that it is universals that are definable(Ζ.11, 1036^a29). Consider as a definiendum auniversal, such asman, and its definiens,rationalanimal. The parts of this definiens are the universalsrational andanimal. If these parts are, in turn,definable, then each should be replaced, in the definition ofman, with its own definition, and so on. In this way thecomplete and adequate definition of a universal such asmanwill contain no parts that are further definable. All proper, orcompletely analyzed, definitions are ultimately composed of simpleterms that are not further definable.

But the implication of this idea for the definitions of hylomorphiccompounds is obvious: since matter appears to be a part of such acompound, the definition of the compound will include, as a part, thedefinitions of its material components. And this consequence seemsimplausible to Aristotle. A circle, for example, seems to be composedof two semicircles (for it obviously may be divided into twosemicircles), but the definition ofcircle cannot be composedof the definitions of its two semicircular parts. For, as Aristotlepoints out (1035^b9),semicircle is defined interms ofcircle, and not the other way around. His point iswell taken, for if circles were defined in terms of semicircles, thenpresumably semicircles would be defined in terms of thequarter-circles of which they are composed, and so on,adinfinitum. The resulting infinite regress would make itimpossible to definecircle at all, for one would never reachthe ultimate “simple” parts of which such a definitionwould be composed.

Aristotle flirts with the idea of distinguishing between differentsenses in which one thing can be a part of another(1034^b33), but instead proposes a different solution: tospecify carefully the whole of which the matter is allegedly a part.“And of the compound statue the bronze is a part, but of what issaid to be a statue as form it is not a part”(1035^a6). Similarly, “even if the line, when divided,passes away into the halves, or the human into the bones, sinews, andflesh, it is not the case that because of this they are composed ofthese as being parts of the substance”(1035^a17–20). Rather, “what is divided intothese as into matter is not the substance but the compound”(1035^b20–1).

In restating his point “yet more perspicuously”(1035^b4), Aristotle notes parenthetically another importantaspect of his theory of substance. He reiterates the priority of form,and its parts, to the matter into which a compound is divided, andnotes that “the soul of animals (for this is substance of theanimate) is the substance that is in accord with the account and isthe form and the essence” (1035^b14–5). The idearecurs in Ζ.11, where he announces that “it is clear toothat the soul is primary substance, whereas the body is matter”(1037^a5). It is further developed, in theMetaphysics, in Ζ.17, as we will see below, andespecially inDe Anima. For more detail on this topic, seeSection 3 of the entry onAristotle’s psychology.

Returning now to the problem raised by the apparent need to refer tomatter in the definition of a substance, we may note that the solutionAristotle offered in Ζ.10 is only partially successful. His pointseems to be that whereas bronze may be a part of a particular statue,neither that particular batch of bronze nor even bronze in generalenters into the essence of statue, since being made of bronze is nopart of what it is to be a statue. But that is only because statues,although they must be made of some kind of matter, do not require anyparticular kind of matter. But what about kinds of substances that dorequire particular kinds of matter? Aristotle’s distinctionbetween form and compound cannot be used in such cases to isolateessence from matter. Thus there may after all be reasons for thinkingthat reference to matter will have to intrude into at least somedefinitions.

In Ζ.11, Aristotle addresses just such a case (although thepassage is difficult and there is disagreement over itsinterpretation). “The form of the human is always found in fleshand bones and parts of this sort,” Aristotle writes(1036^b4). The point is not just that each particular manmust be made of matter, but that each one must be made of matter of aparticular kind—flesh and bones, etc. “Some things,”he continues, “presumably are this in this”(1036^b23), i.e., a particular form in a particular kind ofmatter, so that it is not possible to define them without reference totheir material parts (1036^b28). Nevertheless, Aristotleends Ζ.11 as if he has defended the claim that definition is ofthe form alone. Perhaps his point is that whenever it is essential toa substance that it be made of a certain kind of matter (e.g., thatman be made of flesh and bones, and that one “could not make asaw of wool or wood,” Η.4, 1044^a28) this is insome sense a formal or structural requirement. A kind of matter, afterall, can itself be analyzed hylomorphically—bronze, for example,is a mixture of copper and tin according to a certain ratio or formula(logos), which is in turn predicated of some more genericunderlying subject. The reference to matter in a definition will thusalways be to a certain kind of matter, and hence to a predicate,rather than a subject. At any rate, if by ‘matter’ one hasin mind the ultimate subject alluded to in Ζ.3 (so-called‘prime matter’), there will be no reference to it in anydefinition, “for it is indefinite”(1037^a27).

Ζ.12 introduces a new problem about definitions—theso-called “unity of definition.” The problem is this:definitions are complex (a definiens is always some combination ofterms), so what accounts for the definiendum beingone thing,rather than many (1037^b10)? Suppose that man is defined astwo-footed animal; “why, then, is this one and notmany—animaland two-footed?”(1037^b13–14). Presumably, Aristotle has in mind hisdiscussion in Ζ.4 of such “accidental unities” as apale man. The difference cannot be that our language contains a singleword (‘man’) for a two-footed animal, but no single wordfor a pale man, for Aristotle has already conceded(1029^b28) that we might very well have had a single term(he suggestshimation, literally ‘cloak’) for apale man, but that would still not make the formula ‘paleman’ a definition norpale man an essence(1030^a2).

Aristotle proposes a solution that applies to definitions reached bythe “method of division.” According to this method (seeAristotle’s logic), one begins with the broadest genus containing the species to bedefined, and divides the genus into two sub-genera by means of somedifferentia. One then locates the definiendum in one of thesub-genera, and proceeds to divide this by another differentia, and soon, until one arrives at the definiendum species. This is a classicdefinition by genus and differentia. Aristotle’s proposal isthat “the division should take the differentia of thedifferentia” (1038^a9). For example, if one uses thedifferentiafooted to divide the genusanimal, onethen uses a differentia such ascloven-footed for the nextdivision. If one divides in this way, Aristotle claims, “it isevident that the ultimate (or completing,teleutaia)differentia will be the substance of the thing and itsdefinition” (1038^a19). For each “differentia ofa differentia” entails its predecessor (being cloven-footedentails being footed), and so the long chain of differentiae can bereplaced simply by the ultimate differentia, since it entails all ofits predecessors. As Aristotle points out, it would be redundant toinclude any of the differentiae in the chain other than the ultimateone: “when we say footed two-footed animal … we shall besaying the same thing several times over”(1038^a22–24).

This proposal shows how a long string of differentiae in a definitioncan be reduced to one, but it does not solve the problem of the unityof definition. For we are still faced with the apparent fact thatgenus + differentia constitutes a plurality even if the differentia isthe ultimate, or “completing,” one. It is not surprising,then, that Aristotlereturns to the problem of unity later (Η.6) and offers a different solution.

10. Substances and Universals

At this point, we seem to have a clear idea about the nature ofsubstantial form as Aristotle conceives of it. A substantial form isthe essence of a substance, and it corresponds to a species. Since itis an essence, a substantial form is what is denoted by the definiensof a definition. Since only universals are definable, substantialforms are universals. That substantial forms are universals isconfirmed by Aristotle’s comment, at the end of Ζ.8, that“Socrates and Callias … are distinct because of theirmatter … but the same in form”(1034^a6–8). For them to be the same in form is forthem to have the same form, i.e., for one and the same substantialform to be predicated of two different clumps of matter. And being“predicated of many” is what makes something a universal(De Interpretatione 17^a37).

But Ζ.13 throws our entire understanding into disarray. Aristotlebegins by returning to the candidates for the title ofousiaintroduced in Ζ.3, and points out that having now discussed theclaims of the subject and the essence, it is time to consider thethird candidate, the universal. But the remainder of the chapterconsists of a barrage of arguments to the conclusion that universalsare not substances.

Ζ.13 therefore produces a fundamental tension inAristotle’s metaphysics that has fragmented his interpreters.Some maintain that Aristotle’s theory is ultimatelyinconsistent, on the grounds that it is committed to all three of thefollowing propositions:

(i)	Substance is form.
(ii)	Form is universal.
(iii)	No universal is a substance.

Others have provided interpretations according to which Aristotle doesnot maintain all of (i)–(iii), and there is a considerablevariety of such interpretations, too many to be canvassed here. Butthere are two main, and opposed, lines of interpretation. According toone, Aristotle’s substantial forms are not universals after all,but each belongs exclusively to the particular whose form it is, andthere are therefore as many substantial forms of a given kind as thereare particulars of that kind. According to the other,Aristotle’s arguments in Ζ.13 are not intended to show thatno universal is a substance,tout court, but some weakerthesis that is compatible with there being only one substantial formfor all of the particulars belonging to the same species. Proponentsof particular forms (or essences) include Sellars 1957, Harter 1975,Hartman 1977, Irwin 1988, and Witt 1989b. Opponents include Woods1967, Owen 1978, Code 1986, Loux 1991, and Lewis 1991.

It would be foolish to attempt to resolve this issue within theconfines of the present entry, as it is perhaps the largest, and mostdisputed, single interpretative issue concerning Aristotle’sMetaphysics. We will, instead, mention some of the mainconsiderations brought up on each side of this dispute, and give ourreasons for thinking that substantial forms are universals.

The idea that substantial forms are particulars is supported byAristotle’s claims that a substance is “separable and thissomething” (chôriston kai tode ti, Ζ.3),that there are no universals apart from their particulars (Ζ.13),and that universals are not substances (Ζ.13). On the other side,the idea that substantial forms are universals is supported byAristotle’s claims that substances are,par excellence,the definable entities (Ζ.4), that definition is of the universal(Ζ.11), and that it is impossible to define particulars(Ζ.15).

In our opinion, the indefinability of particulars makes it impossiblefor substantial forms to be particulars. If there were a substantialform that is unique to some sensible particular, say Callias, then thedefinition corresponding to that form, or essence, would applyuniquely to Callias—it would define him, which is precisely whatAristotle says cannot be done. The question, then, is whether theevidence against substantial forms being universals can be countered.This is less clear, but the following considerations are relevant. (1)Aristotle’s claim that a substantial form is an individual(tode ti) does not exclude its being a universal(katholou). Universals are contrasted with particulars(kath’ hekasta), not individuals (although Aristotledoes sometimes ignore the distinction betweentode ti andkath’ hekaston). What makes something atodeti is its being a fully determinate thing, not furtherdifferentiable; what makes something akath’ hekastonis its being a particular thing, unrepeatable, and not predicated ofanything else. There is thus the possibility of a universaltodeti—a fully determinate universal not further divisible intolower-level universals, but predicated of numerous particulars. (2)The claim that there are no universals apart from particulars needs tobe understood in context. When Aristotle asserts (1038^b33)that “there is not some animal … beyond the particularones (ta tina)” he is just as likely to be referring tothe particularkinds of animals as he is to particularspecimens. If so, his point may be that a generic kind, such asanimal, is ontologically dependent on its species, and hence on thesubstantial forms that are the essences of those species. (3) Thearguments of Ζ.13 against the substantiality of universals arepresented as part of a give-and-take investigation of the perplexitiesinvolved in the notion of substantial form. It is not clear,therefore, whether the blanket claim “No universal is asubstance” is intended to be accepted without qualification.Indeed, a closer examination of the arguments may show thatqualifications are required if the arguments are to be cogent. Forexample, the argument at 1038^b11–15 is based on thepremise that the substance ofx is peculiar (idion)tox. It then draws the conclusion that a universal cannot bethe substance of all of its instances (for it could not beidion to all of them), and concludes that it must be thesubstance “of none.” But note that this conclusion doesnot say that no universal can be a substance, but only that nouniversal can be the substance of any of its instances (cf. Code1978). Aristotle’s point may be that since form is predicated ofmatter, a substantial form is predicated of various clumps of matter.But it is not the substance of those clumps of matter, for it ispredicated accidentally of them. The thing with which it is uniquelycorrelated, and of which it is the substance, is not one of itsinstances, but is the substantial formitself. Thisconclusion should not be surprising in light of Aristotle’sclaim in Ζ.6 that “each substance is one and the same asits essence.” A universal substantial form just is thatessence.

11. Substance as Cause of Being

In Ζ.17 Aristotle proposes a new point of departure in his effortto say what sort of a thing substance is. The new idea is that asubstance is a “starting-point and cause” (archêkai aitia, 1041^a9) of being. Before looking at thedetails of his account, we will need to make a brief detour intoAristotle’s theory of causes. The relevant texts arePhysics II.3,PosteriorAnalytics II.11,andMetaphysics Α.3 and Δ.2. See also the entryonAristotle’s natural philosophy and Section 2 of the entry onAristotle’s psychology.

The wordaitia (“cause” or, perhaps better,“explanation”), Aristotle tells us, is “said in manyways.” In one sense, a cause is “that out of which a thingcomes to be, and which persists; e.g., bronze, silver, and the genusof these are causes of a statue or a bowl” (Physics194^b24). A cause in this sense has been traditionallycalled amaterial cause, although Aristotle himself did notuse this label. In a second sense, a cause is “the form …the account of the essence” (194^b27), traditionallycalled theformal cause. A third sense, traditionally calledtheefficient cause, is “the primary source of changeor rest” (194^b30). In this sense, Aristotle says, anadviser is the cause of an action, a father is the cause of his child,and in general the producer is the cause of the product. Fourth iswhat is traditionally called thefinal cause, which Aristotlecharacterizes as “the end (telos), that for which athing is done” (194^b33). In this sense, he says,health is the cause of walking, since we might explain aperson’s walking by saying that he walks in order to behealthy—health is what the walking isfor. Note that,as in this case, “things may be causes of one another—hardwork of fitness, and fitness of hard work—although not in thesame sense: fitness is what hard work is for, whereas hard work isprinciple of motion” (195^a10). So hard work is theefficient cause of fitness, since one becomes fit by means of hardwork, while fitness is the final cause of hard work, since one workshard in order to become fit.

Although Aristotle is careful to distinguish four different kinds ofcause (or four different senses of ‘cause’), it isimportant to note that he claims that one and the same thing can be acause in more than one sense. As he puts it, “form, mover, andtelos often coincide” (198^a25). And inDe Anima he is perfectly explicit that the soul, which is theform or essence of a living thing, “is a cause in three of theways we have distinguished” (415^b10)—efficient,formal, and final.

Let us return to Aristotle’s discussion in Ζ.17. The job ofa cause or principle of being, he notes, is to explain why one thingbelongs to another (1041^a11); that is, it is to explainsome predicational fact. What needs to be explained, for example, iswhythis is a man, orthat is a house. But what kindof a question is this? The only thing that can be a man is a man; theonly thing that can be a house is a house. So we would appear to beasking why a man is a man, or why a house is a house, and these seemto be foolish questions that all have the same answer: because eachthing is itself (1041^a17–20). The questions musttherefore be rephrased by taking advantage of the possibility of ahylomorphic analysis. We must ask, e.g., “why arethese—for example, brick and stones—a house?”(1041^a26). The answer Aristotle proposes is that the causeof being of a substance (e.g., of a house) is the form or essence thatis predicated of the matter (e.g., of the bricks and stones) thatconstitute that substance. The essence is not always just a formalcause; in some cases, Aristotle says, it is also a final cause (hegives the examples of a house and a bed), and in some cases anefficient cause (1041^a29–30). But in any case“what is being looked for is the cause in virtue of which thematter is something—and this is the substance”(1041^b6–9) and “the primary cause of itsbeing” (1041^b27).

Notice that the explanandum in these cases (“why is this aman?” or “why is that a house?”) involves a speciespredication (“Callias is a man,” “Fallingwater is ahouse”). But the answer Aristotle proposes invokes a hylomorphicanalysis of these questions, in which form is predicated of matter. SoCallias is a man because the form or essence of man is present in theflesh and bones that constitute the body of Callias; Fallingwater is ahouse because the form of house is present in the materials of whichFallingwater is made. In general, a species predication is explainedin terms of an underlying form predication, whose subject is not theparticular compound but its matter. Form predications are thus morebasic than their corresponding species predications. A substantialform, as a primary definable, is its own substance, for it isessentially predicated of itself alone. But the substantial form of amaterial compound, because it is predicated (accidentally) of thematter of the compound, is the cause of the compound’s being thekind of thing that it is. The form is therefore, in a derivative way,the substance of the compound, as well.

12. Actuality and Potentiality

InMetaphysics Ζ, Aristotle introduces the distinctionbetween matter and form synchronically, applying it to an individualsubstance at a particular time. The matter of a substance is the stuffit is composed of; the form is the way that stuff is put together sothat the whole it constitutes can perform its characteristicfunctions. But soon he begins to apply the distinction diachronically,across time. This connects the matter/form distinction to another keyAristotelian distinction, that between potentiality (dunamis)and actuality (entelecheia) or activity (energeia).This distinction is the main topic of Book Θ.

Aristotle distinguishes between two different senses of the termdunamis. In the strictest sense, adunamis is thepower that a thing has to produce a change. A thing has adunamis in this sense when it has within it “astarting-point of change in another thing or in itself insofar as itis other” (Θ.1, 1046^a12; cf. Δ.12). Theexercise of such a power is akinêsis—a movementor process. So, for example, the housebuilder’s craft is a powerwhose exercise is the process of housebuilding. But there is a secondsense ofdunamis—and it is the one in which Aristotleis mainly interested—that might be better translated as‘potentiality’. For, as Aristotle tells us, in this sensedunamis is related not to movement (kinêsis)but to activity (energeia)(Θ.6, 1048^a25). Adunamis in this sense is not a thing’s power to producea change but rather its capacity to be in a different and morecompleted state. Aristotle thinks that potentiality so understood isindefinable (1048^a37), claiming that the general idea canbe grasped from a consideration of cases. Activity is to potentiality,Aristotle tells us, as “what is awake is in relation to what isasleep, and what is seeing is in relation to what has its eyes closedbut has sight, and what has been shaped out of the matter is inrelation to the matter” (1048^b1–3).

This last illustration is particularly illuminating. Consider, forexample, a piece of wood, which can be carved or shaped into a tableor into a bowl. In Aristotle’s terminology, the wood has (atleast) two different potentialities, since it is potentially a tableand also potentially a bowl. The matter (in this case, wood) is linkedwith potentialty; the substance (in this case, the table or the bowl)is linked with actuality. The as yet uncarved wood is only potentiallya table, and so it might seem that once it is carved the wood isactually a table. Perhaps this is what Aristotle means, but it ispossible that he does not wish to consider the wood to be a table. Hisidea might be that not only can a piece of raw wood in thecarpenter’s workshop be considered a potential table (since itcan be transformed into one), but the wood composing the completedtable is also, in a sense, a potential table. The idea here is that itis not the wood qua wood that is actually a table, but the wood quatable. Considered as matter, it remains only potentially the thingthat it is the matter of. (A contemporary philosopher might make thispoint by refusing to identify the wood with the table, saying insteadthat the wood only constitutes the table and is not identical to thetable it constitutes.)

Since Aristotle gives form priority over matter, we would expect himsimilarly to give actuality priority over potentiality. And that isexactly what we find (Θ.8, 1049^b4–5). Aristotledistinguishes between priority inlogos (account ordefinition), in time, and in substance. (1) Actuality is prior inlogos since we must cite the actuality when we give anaccount of its corresponding potentiality. Thus, ‘visible’means ‘capable ofbeing seen’;‘buildable’ means ‘capable ofbeingbuilt’(1049^b14–16). (2) As regardstemporal priority, by contrast, potentiality may well seem to be priorto actuality, since the wood precedes the table that is built from it,and the acorn precedes the oak that it grows into. Nevertheless,Aristotle finds that even temporally there is a sense in whichactuality is prior to potentiality: “the active that is the samein form, though not in number [with a potentially existing thing], isprior [to it]” (1049^b18–19). A particular acornis, of course, temporally prior to the particular oak tree that itgrows into, but it is preceded in time by the actual oak tree thatproduced it, with which it is identical in species. The seed(potential substance) must have been preceded by an adult (actualsubstance). So in this sense actuality is prior even in time.

(3) Aristotle argues for the priority in substance of actuality overpotentiality in two ways. (a) The first argument makes use of hisnotion of final causality. Things that come to be move toward an end(telos)—the boy becomes a man, the acorn becomes anoak—and “the activity is the end, and it is for the sakeof this that the capacity [or potentiality] is acquired. For animalsdo not see in order that they may have sight, rather they have sightin order that they may see … matter is potentially somethingbecause it may come in the form of it—at any rate, when it isactively something, then itis in the form of it”(1050^a9–17). Form or actuality is the end towardwhich natural processes are directed. Actuality is therefore a causein more than one sense of a thing’s realizing its potential. Aswe noted in Section 11, one and the same thing may be the final,formal, and efficient cause of another. Suppose an acorn realizes itspotential to become an oak tree. The efficient cause here is theactual oak tree that produced the acorn; the formal cause is thelogos defining that actuality; the final cause is thetelos toward which the acorn develops—an actual(mature) oak tree.

(b) Aristotle also offers (1050^b6–1051^a2)an “even stricter” argument for his claim that actualityis prior in substance to potentiality. A potentiality is for either ofa pair of opposites; so anything that is capable of being is alsocapable of not being. What is capable of not being might possibly notbe, and what might possibly not be is perishable. Hence anything withthe mere potentiality to be is perishable. What is eternal isimperishable, and so nothing that is eternal can exist onlypotentially—what is eternal must be fully actual. But theeternal is prior in substance to the perishable. For the eternal canexist without the perishable, but not conversely, and that is whatpriority in substance amounts to (cf. Δ.11, 1019^a2).So what is actual is prior in substance to what is potential.

13. Unity Reconsidered

In Η.6, Aristotle returns to the problem of the unity ofdefinition (discussed above in Section 9) and offers a new solution based on the concepts of potentiality andactuality. He begins by pointing out (recalling the language ofΖ.17) that the things whose unity he is trying to explain arethose “that have several parts and where the totality of them isnot like a heap, but the whole is something beyond the parts”(1045^a8–10). His task is to explain the unity of suchcomplexes.

The problem is insoluble, he says, unless one realizes that“there is on the one hand matter and on the other shape (orform,morphê), and the one is potentially and the otheractively.” Once one realizes this, “then what we areinquiring into will no longer seem to be a puzzle”(1045^a20–25). He offers the following example(1045^a26–35). Supposeround bronze were thedefinition of ‘cloak’. If someone were to ask “whatmakes a cloak one thing, a unity?” the answer would be obvious.For bronze is the matter, and roundness is the form. The bronze ispotentially round, and round is what the bronze actually is when ithas received this form. The cause of the unity of the cloak (in thissense of ‘cloak’) is just the cause of bronze being maderound. Since the cloak is something that was produced, or brought intobeing, there is no cause of its unity other than the agent who put theform into the matter. Bronze (the matter) is a potential sphere, andthe cloak is an actual sphere. Butround bronze is equallythe essence of both the actual sphere and the potential one. Thebronze and the roundness are not two separate things. The bronze ispotentially a sphere, and when it is made round it constitutes anactual one—a single sphere of bronze.

It is easy to see how this hylomorphic analysis explains the unity ofa substantial material particular, since neither the matter nor theform of such a particular is by itself a single material individual,and it is only when they are taken together that they constitute suchan individual. But the question Aristotle is trying to answer is this:“why on earth is something one when the account of it is what wecall a defnition?” (Ζ.12, 1037^b11). Since properdefinables are universals, it remains to be seen how the proposedsolution applies to them. After all, universals are not materialobjects, and so it is not clear how they can be viewed as hylomorphiccompounds. But Aristotle has at his disposal a concept that can fillthis bill perfectly, viz., the concept of intelligible matter(hulê noêtê). (The main purpose ofintelligible matter is to provide something quasi-material for puregeometrical objects that are not realized in bronze or stone, forexample, to be made of.) So we surmise that it is for this reason thatAristotle goes on (1045^a33) to introduce matter into thecurrent context. If this is so, we may conclude that the materialcomponent in the definition of a species is intelligible matter.Elsewhere, he explicitly describes genus as matter: “the genusis the matter of what it is said to be the genus of” (Ι.8,1058a23). So a species too, although it is not itself a materialobject, can be considered a hylomorphic compound. Its matter is itsgenus, which is only potentially the species defined; its differentiais the form that actualizes the matter. The genus does not actuallyexist independently of its species any more than bronze exists apartfrom all form. The genusanimal, for example, is just thatwhich is potentially some specific kind of animal or other. Aristotleconcludes (1045^b17–21) that “the ultimatematter and the form (morphê) are one and the same, theone potentially, the other actively … and what potentially isand what actively is are in a way one.”

This solution, of course, applies only to hylomorphic compounds. Butthat is all it needs to do, according to Aristotle. For he ends thechapter by claiming that the problem of unity does not arise for otherkinds of compounds that are not material: “Things that have nomatter … are all unconditionally just what is a one”(1045^b23).

14. Theology

The science of being qua being is a science of form. But it is alsotheology, the science of god. The question now is, how can it be both?And to it Aristotle gives a succinct answer:

If there is some immovable substance, this [that is, theologicalphilosophy] will be prior and will be primary philosophy, and it willbe universal in this way, namely, because it is primary. And it willbelong to it to get a theoretical grasp on being qua being, both whatit is and the things that belong to it insofar as it is being. (E.1,1026^a29–32)

So the primacy of theology, which is based on the fact that it dealswith substance that is eternal, immovable, and separable, issupposedly what justifies us in treating it as the universal scienceof being qua being.

A reminder, first, of what this primacy is. As we saw in Sections2–3 above, only beings in the category of substance areseparable, so that they alone enjoy a sort of ontological prioritythat is both existential and explanatory. Thus walking and beinghealthy are characterized as “incapable of beingseparated,” on the grounds that there is some particularsubstantial underlying subject of which they are predicated (Z.1,1028^a20–31). Often, indeed, separability isassociated with being such a subject: “The underlying subject isprior, which is why the substance is prior” (Δ.11,1019^a5–6); “If we do not posit substances to beseparated, and in the way in which particular things are said to beseparated, we will do away with the sort of substance we wish tomaintain” (M.10, 1086^b16–19). Similarly, notbeing separable is associated with being predicated of such a subject:“All other things are either said of primary substances assubjects or in them as subjects. Therefore, if there were no primarysubstances, there could not be anything else” (Cat.2^b3–6). The starting-points and causes of all beings,then, must be substances. But for all that has been shown so far, theuniverse could still be made up of lots of separate substances havinglittle ontologically to do with each other.

Here it may serve to return to Z.3, which opens by calling attentionto something said (legomenon) about substance, namelythat:

Something is said to be (legetai) substance, if not in moreways, at any rate most of all in four. For the essence, the universal,and the genus seem to be the substance of each thing, and fourth ofthese, the underlying subject. (1028^b33–36)

Since “the primary underlying subject seems most of all to besubstance” (1029^a1–2), because what is said orpredicated of it depends on it, the investigation begins with thissubject, quickly isolating three candidates: the matter, the compoundof matter and form, and the form itself (1029^a2–3),which is identical to essence (1032^b1–2). Almost asquickly (1029^a7–32), the first two candidates are atleast provisionally excluded. A—perhapsthe—majorground for their exclusion is theprimacy dilemma, which weshall now briefly investigate.

The philosophical background to the dilemma is this. If you are arealist about scientific knowledge and truth, as Aristotle is, thestructure of your scientific theories must mirror the structure ofreality, so that scientific starting-points or first principles, mustalso be the basic building blocks of reality. Suppose that this is notso. Suppose that your physics tells you that atoms are the basicbuilding blocks of reality and that your psychology tells you thatsense-perceptions are the starting-points of scientific knowledge.Then you will face a very severe problem, that of skepticism. For awedge can be driven between the starting-points of scientificknowledge and reality’s basic building blocks. RenéDescartes’ famous dreaming argument is one familiar form such awedge might take. Your sense-perceptions are consistent with yourbeing always asleep and having a very detailed dream.

In B.6, Aristotle introduces a similar problem about the relationbetween our scientific representation of the world and how the worldin itself is structured:

We must … ask whether [the starting-points] are universal orexist in the way we say particulars do. For if they are universal,they will not be substances. For no common thing signifies a thissomething but a such-and-such sort of thing, whereas substance is athis something.… If then the starting-points are universals,these things follow. But if they are not universals, but [exist] asparticulars, they will not be scientifically knowable. For scientificknowledge of all things is universal. Thus there will be otherstarting-points prior to the starting-points, namely, those that arepredicated universally, if indeed there is going to be scientificknowledge of these. (1003^a7–17)

The basic building blocks of reality, (Aristotelian) science tells us,are particular matter-form compounds. Yet science’s ownstarting-points are the forms—the universal essences—ofsuch things. There is no science of you, or of me, though there is oneof human beings. How, then, can science possibly be reflectingaccurately the structure of reality, when its starting-points andthose of reality fail so radically to map onto each other? For thereis no greater difference, it seems, than that between particulars anduniversals. The thing to do, then, given that science provides ourbest access to the nature of reality, is to investigate the universalforms or essences that are basic to it.

Aristotle begins the investigation with the most familiar and widelyrecognized case, which is the form or essence present in sublunarymatter-form compounds. It is announced in Z.3(1029^b3–12), but not begun until some chapters laterand not really completed until the end of Θ.5. And by then it iswith actuality (entelecheia) or activity (energeia)that form is identified, and matter with potentiality. The science ofbeing qua being can legitimately focus on form, or actuality, then, asthe factor common to all substances, and so to all the beings. Butunless it can be shown that there is some explanatory connectionbetween the forms of all these substances, the non-fragmentary natureof being itself will still not have been established, and the picturesgiven to us by the various sciences will, so to speak, be separatepictures, and the being they collectively portray, divided.

The next stage in the unification of being, and the legitimation ofthe science dealing with it qua being, is effected by an argument inΛ.6 that trades on the identification of form with actualityand matter with potentiality:

If there is something that is capable of moving things or acting onthem, but that is not actively doing so, there will not [necessarily]be movement, since it is possible for what has a capacity not toactivate it. There is no benefit, therefore, in positing eternalsubstances, as those who accept the Forms do, unless there is to bepresent in them some starting-point that is capable of causing change.Moreover, even this is not enough, and neither is another substancebeyond the Forms. For if it will not be active, there will not bemovement. Further, even if it will be active, it is not enough, if thesubstance of it is a capacity. For then there will not beeternal movement, since what is potentially may possibly notbe. There must, therefore, be such a starting-point, the verysubstance of which is activity. Further, accordingly, these substancesmust be without matter. For they must be eternal, if indeedanything else is eternal. Therefore they must be activity.(1071^b12–22)

Matter-form compounds are, as such, capable of movement and change.The canonical examples of them—perhaps the only genuine or fullyfledged ones—are living metabolizing beings (Z.17,1041^b29–30). But if these beings are to be actual,there must be substances whose very essence isactivity—substances that do not need to be activated bysomething else.

With matter-form compounds shown to be dependent on substantialactivities for their actual being, a further element of verticalunification is introduced into beings, since layer-wise the two sortsof substances belong together. Laterally, though, disunity continuesto threaten. For as yet nothing has been done to exclude thepossibility of each compound substance having a distinct substantialactivity as its own unique activator. Being, in that case, would be aset of ordered pairs, the first member of which would be a substantialactivity, the second a matter-form compound, with all its dependentattributes.

InMetaphysics Λ.8 Aristotle initially takes a step inthe direction of such a bipartite picture. He asks how manysubstantial activities are required to explain astronomical phenomena,such as the movements of the stars and planets, and answers that theremust be forty-nine of them (1074^a16). But these forty-nineare coordinated with each other so as to form a system. And whatenables them to do so, and to constitute a single heaven, is thatthere is a single prime mover of all of them:

It is evident that there is but one heaven. For if there are many, asthere are many human beings, the starting-point for each will be onein form but in number many. But all things that are many in numberhave matter, for one and the same account applies to many, forexample, human beings, whereas Socrates is one. But the primaryessence does not have matter, since it is an actuality. The primaryimmovable mover, therefore, is one both in account and in number. Andso, therefore, is what is moved always and continuously. Therefore,there is only one heaven. (1074^a31–38)

What accounts for the unity of the heaven, then, is that the movementsin it are traceable back to a single cause: the prime or primarymover.

Leaving aside the question of just how this primary mover moves whatit moves directly, the next phase in the unification of beings is theone in which the sublunary world is integrated with the alreadyunified superlunary one studied by astronomy. This takes place inΛ.10. One obvious indication of this unification is thedependence of the reproductive cycles of plants and animals on theseasons, and their dependence, in turn, on the movements of the sunand moon (Λ.5, 1071^a13–16). And beyond eventhis there is the unity of the natural world itself, which ismanifested in the ways in which its inhabitants are adapted to eachother:

All things are jointly organized in a way, although not in the sameway—even swimming creatures, flying creatures, and plants. Andthe organization is not such that one thing has no relation to anotherbut rather there is a relation. For all things are jointly organizedin relation to one thing—but it is as in a household, where thefree men least of all do things at random, but all or most of thethings they do are organized, while the slaves and beasts can do alittle for the common thing, but mostly do things at random. For thisis the sort of starting-point that the nature is of each of them. Imean, for example, that all must at least come to be disaggregated[into their elements]; and similarly there are other things which theyall share for the whole. (1075^a16–25)

Thus the sublunary realm is sufficiently integrated with thesuperlunary one that we can speak of them as jointly having a natureand a ruler, and as being analogous to an army (1075^a13)and a household (1075^a22).

We may agree, then, that the divine substances in the superlunaryrealm and the compound substances in the sublunary one have primafacie been vertically integrated into a single explanatory system. Asa result, when we look at the form of a sublunary matter-formcompound, we will find in it the mark of a superlunary activator, justas we do in the case of the various heavenly bodies, and, as in theline of its efficient causes, we find “the sun and its movementin an inclined circle” (1071^a15–16). Stillawaiting integration, though, are mathematical objects, such asnumbers. But in Books M and N these are shown to be not substantialstarting-points and causes but abstractions from perceptible sublunarybeings—they are dependent entities, in other words, rather thanself-subsistent ones. Similarly, inPhysics II.2 we read:

The mathematician too busies himself about these things [planes,solids, lines, and points], although not insofar as each of them isthe limit of a natural body, nor does he get a theoretical grasp onthe coincidents of natural bodies insofar as they are such. That iswhy he separates them. For they are separable in the understandingfrom movement, and so their being separated makes no difference, nordoes any falsehood result from it. (193^b31–35)

This completes the vertical and horizontal unification of being:attributes depend on substances, substantial matter-form compoundsdepend on substantial forms, or activities, numbers depend onmatter-form compounds.

Beings are not said to be “in accord with one thing,”therefore, as they would be if they formed a single first-order genus,but “with reference to one thing,” namely, a divinesubstance that is in essence an activity. And it is this more complexunity, compatible with generic diversity, and a genuine multiplicityof distinct first-order sciences, but just as robust and wellgrounded, that grounds and legitimates the science of being qua beingas a single science dealing with a genuine object of study (Γ.2,1003^b11–16). The long argument that leads to thisconclusion is thus a sort of proof of the existence, and so of thepossibility, of the science on which theMetaphysics focuses.It is also the justification for the claim, which we looked at before,that the science of being qua being is in fact theology(1026^a27–32).

There, then, in the starry heavens above us, are the forty-ninecelestial spheres, all moving eternally in fixed circular orbits. Theoutermost one, which contains all the others, is the primary heaven.Questions immediately arise: (i) how is the primary heaven moved bythe primary mover, the primary god? Aristotle gives his response inΛ.7:

There is something [namely, the primary heaven,] that is always movedwith an unceasing movement, which is in a circle (and this is clearnot from argument alone but also from the facts). So the primaryheaven would be eternal. There is, therefore, also something thatmoves it [namely, the primary god]. But since what is moved and movessomething is something medial, there is something that moves withoutbeing moved, being eternal, substance, and activity. This, though, isthe way the object of desire and the intelligible object move things:they move them without being moved. Of these objects, the primary onesare the same. (1072^a21–27)

Thus the primary heaven is moved by the primary god, in the way thatwe are moved by a good that we desire. (That this heaven, as well asthe other heavenly bodies, are therefore alive is argued for inDeCaelo II.12.) But (ii) how can the primary god be such a good?Moreover, (iii) why is he not moved by something else again?

The answer to question (ii) is also found in Λ.7:

Active understanding, though, is intrinsically of what isintrinsically best, and the sort that is to the highest degree best isof what is to the highest degree best. The understanding activelyunderstands itself by partaking of the intelligible object. (For itbecomes an intelligible object by touching and understanding one, sothat understanding and intelligible object are the same.) For what isreceptive of the intelligible object and of the substance is theunderstanding, and it is active when it possesses it, so that thisrather than that seems to be the divine thing that understandingpossesses, and contemplation seems to be most pleasant and best. If,then, that good state [of activity], which we are sometimes in, the[primary] god is always in, that is a wonderful thing, and if to ahigher degree, that is yet more wonderful. But that is his state. Andlife, too, certainly belongs to him. For the activity of understandingis life, and he is that activity; and his intrinsic activity is lifethat is best and eternal. (1072^b18–28)

What the primary heaven is moved by, then, is the wish to be in thegood state of active contemplation that we, when we are happiest, arein, and that the primary god is always in because he justisthat activity. Just as we seek the good that the primary god is, sotoo does the primary heaven and its forty-eight celestialcompanions.

This brings us to question (iii). When the understanding is activelycontemplating something, that something—that intelligibleobject—is what activates it. So why isn’t that object yetmore primary than the primary god? Aristotle gives his answer inΛ.9; the reasoning, though compressed, should now be fairlyreadily intelligible:

What does it [the primary god] understand? For it is either itself orsomething else. And if something else, then either always the samething or sometimes this and sometimes that. Does it, then, make adifference or none at all whether it actively understands the good orsome random object? Or are there not certain things that it would beabsurd for it to think of? It is clear, therefore, that it activelyunderstands what is most divine and most estimable and does not change[its object], since change would be for the worse, and would alreadybe a sort of movement. First, then, if its substance is not activeunderstanding but rather a capacity [to understand], … it isclear that something else would be more estimable than theunderstanding, namely, what is understood. And indeed [the capacity]to understand and active understanding will belong even to someone whoactively understands the worst thing, so that if this is to be avoided(for there are in fact some things that it is better not to see thanto see), the active understanding would not be the best thing. It isitself, therefore, that it understands, if indeed it is the mostexcellent thing, and the active understanding is active understandingof active understanding (hênoêsisnoêseôs noêsis). (1074^b22–35)

God is the understanding that understands himself, because hisunderstanding is like ours would be if we imagine it as being theintelligible equivalent of seeing light without seeing any othervisible object. From the inside, then, from the point of view of thesubject experiencing it, it is a state of consciousness of a sortfamiliar from the writings of the great religious mystics, in whichboth subject and object disappear from an awareness that yet remainsfully and truly attentive, fully alive and joyous. Insofar as we haveany experience-based evidence of what a beatific state is like, thisone surely approximates to it. Were we to experience it or somethinglike it, then, there is some reason to think that we would agree thatit is bliss indeed, blessed happiness unalloyed. This is theconclusion Aristotle himself comes to and defends inNicomacheanEthics X.6–8. Practical wisdom and theoretical wisdom, itfollows, have the same ultimate starting-point, the same firstprinciple, so that wisdom, too, is something unified.

Go back now to the primacy dilemma and notice that its resolution iswithin our grasp, though one might be forgiven for not readilyunderstanding Aristotle’s statement of it in M.10:

The fact that all scientific knowledge is universal, so that thestarting-points of beings must also be universal and not separatesubstances, involves the greatest puzzle of those mentioned. Butthough there is surely a way in which what is said is true, there isanother way in which it is not true. For scientific knowledge, likeknowing scientifically, is twofold, one potential, the other active:the capacity [or potential], being as matter, universal andindefinite, is of what is universal and indefinite, whereas theactivity, being definite, is of what is definite—being a thissomething of a this something. But it is only coincidentally thatsight sees universal color, because this [particular instance of]color that it sees is a color, and so what the grammariantheoretically grasps, namely, this [particular instance of] A, is anA. For if the starting-points must be universal, what comes from themmust also be universal, as in the case of demonstrations. And if thisis so, there will be nothing separable and no substance either.However, in one way scientific knowledge is universal, but in anotherit is not. (1087^a10–25)

The idea is this. Since forms or essences are universals, you and Imay both know the same form, as we may both know the letter A. Butwhen I actively know or contemplate that universal form, what is nowbefore my mind is a particular: this actualization of that universal.Now consider the primary god. He is eternally and essentially theobject of the active understanding that he is. So he is a substantialparticular. But since he is essentially an activity, he is also auniversal essence of a special sort—one that can only be actual,never merely potential. In a way, then, the primary god overcomes thedifference between particulars and universals that seemedunbridgeable. For he is at once a concrete particular and thestarting-point of all scientific knowledge. He thereby unifies notjust being, but the scientific knowledge of it as well, insuring thatthe latter fits the former in the way that realism requires.

15. Glossary of Aristotelian Terminology

• accident:sumbebêkos
• accidental:kata sumbebêkos
• account:logos
• activity:energeia
• actuality:entelecheia
• alteration:alloiôsis
• affirmative:kataphatikos
• assertion:apophansis (sentence with a truth value,declarative sentence)
• assumption:hupothesis
• attribute:pathos
• axiom:axioma
• be:einai
• being(s):on,onta
• belong:huparchein
• category:katêgoria
• cause:aition,aitia
• change:kinêsis,metabolê
• come to be:gignesthai
• coming to be:genesis
• contradict:antiphanai
• contradiction:antiphasis (in the sense“contradictory pair of propositions” and also in the sense“denial of a proposition”)
• contrary:enantion
• definition:horos,horismos
• demonstration:apodeixis
• denial (of a proposition):apophasis
• dialectic:dialektikê
• differentia:diaphora; specific difference,eidopoiosdiaphora
• distinctive:idios,idion
• end:telos
• essence:to ti ên einai,to ti esti
• essential:en tôi ti esti,en tôi tiên einai (of predications);kath’ hauto (ofattributes)
• exist:einai
• explanation:aition,aitia
• final cause:hou heneka (literally, “what somethingis for”)
• form:eidos,morphê
• formula:logos
• function:ergon
• genus:genos
• homonymous:homônumon
• immediate:amesos
• impossible:adunaton
• in respect of itself:kath’ hauto
• individual:atomon,tode ti
• induction:epagôgê
• infinite:apeiron
• kind:genos,eidos
• knowledge:epistêmê
• matter:hulê
• movement:kinêsis
• nature:phusis
• negation (of a term):apophasis
• particular:en merei,epi meros (of aproposition);kath’hekaston (of individuals)
• peculiar:idios,idion
• per se:kath’ hauto
• perception:aisthêsis
• perplexity:aporia
• possible:dunaton,endechomenon;endechesthai (verb: “be possible”)
• potentially:dunamei
• potentiality:dunamis
• predicate:katêgorein (verb);katêegoroumenon(“what is predicated”)
• predication:katêgoria (act or instance ofpredicating, type of predication)
• principle:archê (starting point of ademonstration)
• qua:hêi
• quality:poion
• quantity:poson
• refute:elenchein; refutation,elenchos
• separate:chôriston
• said in many ways:pollachôs legetai
• science:epistêmê
• soul:psuchê
• species:eidos
• specific:eidopoios (of a differentia that “makes aspecies”,eidopoios diaphora)
• subject:hupokeimenon
• substance:ousia
• term:horos
• this:tode ti
• universal:katholou (both of propositions and ofindividuals)
• wisdom:sophia

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Acknowledgments

We are grateful to István Bodnar for his help in clarifying andimproving our presentation, in the supplement on NonsubstantialParticulars, of Frede’s reading of Aristotle’s definitionof ‘in a subject’ (Cat. 1^a25), and forstressing the underlying similarity between the Frede and Owenreadings.