1028aThe term “being” has several senses, which we have classified in our discussion¹ of the number of senses in which terms are used. It denotes first the “ what” of a thing, i.e. the individuality; and then the quality or quantity or any other such category. Now of all these senses which “being” has, the primary sense is clearly the “what,” which denotes the substance (because when we describe the quality of a particular thing we say that it is “good or bad,” and not “five feet high” or “a man”; but when we describe what it is, we say not that it is “white” or “hot” or “five feet high,” but that it is “a man” or “a god”), and all other things are said to “be” because they are either quantities or qualities or affections or some other such thing. Hence one might raise the question whether the terms “to walk” and “to be well” and “to sit” signify each of these things as “being,” or not; and similarly in the case of any other such terms; for not one of them by nature has an independent existence or can be separated from its substance. Rather, if anything it is the thing which walks or sits or is well that is existent. The reason why these things are more truly existent is because their subject is something definite; i.e. the substance and the individual, which is clearly implied in a designation of this kind, since apart from it we cannot speak of “the good” or “sitting.” Clearly then it is by reason of the substance that each of the things referred to exists. Hence that which is primarily, not in a qualified sense but absolutely, will be substance. Now “primary” has several meanings; but nevertheless substance is primary in all senses, both in definition and in knowledge and in time. For none of the other categories can exist separately, but substance alone; and it is primary also in definition, because in the formula of each thing the formula of substance must be inherent; and we assume that we know each particular thing most truly when we know what “man” or “fire” is— 1028brather than its quality or quantity or position; because we know each of these points too when we know what the quantity or quality is. Indeed, the question which was raised long ago, is still and always will be, and which always baffles us—“What is Being?”—is in other words “What is substance?” Some say that it is one²; others, more than one; some, finite³; others, infinite.⁴ And so for us too our chief and primary and practically our only concern is to investigate the nature of “being” in the sense of substance.

Substance is thought to be present most obviously in bodies. Hence we call animals and plants and their parts substances, and also natural bodies, such as fire, water, earth, etc., and all things which are parts of these or composed of these, either of parts or them or of their totality; e.g. the visible universe and its parts, the stars and moon and sun. We must consider whether (a) these are the only substances, or (b) these and some others, or (c) some of these, or (d) some of these and some others, or (e) none of these, but certain others. Some⁵ hold that the bounds of body—i.e. the surface, line, point and unit—are substances, and in a truer sense than body or the solid. Again, some⁶ believe that there is nothing of this kind besides sensible things, while others believe in eternal entities more numerous and more real than sensible things. Thus Plato posited the Forms and the objects of mathematics as two kinds of substance, and as a third the substance of sensible bodies; and Speusippus⁷ assumed still more kinds of substances, starting with “the One,” and positing principles for each kind: one for numbers, another for magnitudes, and then another for the soul. In this way he multiplies the kinds of substance. Some⁸ again hold that the Forms and numbers have the same nature, and that other things—lines and planes—are dependent upon them; and soon back to the substance of the visible universe and sensible things. We must consider, then, with regard to these matters, which of the views expressed is right and which wrong; and what things are substances; and whether there are any substances besides the sensible substances, or not; and how sensible substances exist; and whether there is any separable substance (and if so, why and how) or no substance besides the sensible ones. We must first give a rough sketch of what substance is.

The term “substance” is used, if not in more, at least in four principal cases; for both the essence and the universal and the genus are held to be the substance of the particular, and fourthly the substrate. The substrate is that of which the rest are predicated, while it is not itself predicated of anything else. Hence we must first determine its nature, 1029afor the primary substrate is considered to be in the truest sense substance. Now in one sense we call the matter the substrate; in another, the shape ; and in a third, the combination of the two. By matter I mean, for instance, bronze; by shape, the arrangement of the form; and by the combination of the two, the concrete thing: the statue. Thus if the form is prior to the matter and more truly existent, by the same argument it will also be prior to the combination. We have now stated in outline the nature of substance—that it is not that which is predicated of a subject, but that of which the other things are predicated. But we must not merely define it so, for it is not enough. Not only is the statement itself obscure, but also it makes matter substance; for if matter is not substance, it is beyond our power to say what else is. For when everything else is removed, clearly nothing but matter remains; because all the other things are affections, products and potencies of bodies, and length, breadth and depth are kinds of quantity, and not substances. For quantity is not a substance; rather the substance is that to which these affections primarily belong. But when we take away length and breadth and depth we can see no thing remaining, unless it be the something bounded by them; so that on this view matter must appear to be the only substance. By matter I mean that which in itself is neither a particular thing nor a quantity nor designated by any of the categories which define Being. For there is something of which each of these is predicated, whose being is different from that of each one of the categories; because all other things are predicated of substance, but this is predicated of matter. Thus the ultimate substrate is in itself neither a particular thing nor a quantity nor anything else. Nor indeed is it the negations of these; for the negations too will only apply to it accidentally. If we hold this view, it follows that matter is substance. But this is impossible; for it is accepted that separability and individuality belong especially to substance. Hence it would seem that the form and the combination of form and matter are more truly substance than matter is. The substance, then, which consists of both—I mean of matter and form—may be dismissed, since it is posterior and obvious. Matter too is in a sense evident. We must consider the third type, for this is the most perplexing. Now it is agreed that some sensible things are substances, and so we should begin our inquiry in connection with these.

1029bIt is convenient to advance to the more intelligible⁹; for learning is always acquired in this way, by advancing through what is less intelligible by nature to what is more so. And just as in actions it is our task to start from the good of the individual and make absolute good good for the individual,¹⁰ so it is our task to start from what is more intelligible to oneself and make what is by nature intelligible intelligible to oneself. Now that which is intelligible and primary to individuals is often but slightly intelligible, and contains but little reality; but nevertheless, starting from that which is imperfectly intelligible but intelligible to oneself, we must try to understand the absolutely intelligible; advancing, as we have said, by means of these very things which are intelligible to us. Since we distinguished at the beginning¹¹ the number of ways in which substance is defined, and since one of these appeared to be essence, we must investigate this. First, let us make certain linguistic statements about it. The essence of each thing is that which it is said to be per se. “To be you” is not “to be cultured,” because you are not of your own nature cultured. Your essence, then, is that which you are said to be of your own nature. But not even all of this is the essence; for the essence is not that which is said to be per se in the sense that whiteness is said to belong to a surface,¹² because “being a surface” is not “being white.” Nor is the essence the combination of both, “being a white surface.” Why? Because the word itself is repeated. Hence the formula of the essence of each thing is that which defines the term but does not contain it. Thus if “being a white surface” is the same as “being a smooth surface,” “white” and “smooth” are one and the same.¹³ But since in the other categories too there are compounds with substance (because there is a substrate for each category, e.g. quality, quantity, time, place and motion), we must inquire whether there is a formula of the essence of each one of them; whether these compounds, e.g. “white man,” also have an essence. Let the compound be denoted by X.¹⁴ What is the essence of X? “But this is not even a per se expression.” We reply that there are two ways in which a definition can be not per se true of its subject: (a) by an addition, and (b) by an omission. In one case the definition is not per se true because the term which is being defined is combined with something else; as if, e.g., in defining whiteness one were to state the definition of a white man. In the other, because something else (which is not in the definition) is combined with the subject; as if, e.g., X were to denote “white man,” and X were defined as “white.” “White man” is white, 1030abut its essence is not “to be white.” But is “to be X” an essence at all? Surely not. The essence is an individual type; but when a subject has something distinct from it predicated of it, it is not an individual type. E.g., “white man” is not an individual type; that is, assuming that individuality belongs only to substances. Hence essence belongs to all things the account of which is a definition. We have a definition, not if the name and the account signify the same (for then all accounts would be definitions; because any account can have a name, so that even “the Iliad” will be a definition), but if the account is of something primary. Such are all statements which do not involve the predication of one thing of another. Hence essence will belong to nothing except species of a genus, but to these only; for in these the predicate is not considered to be related to the subject by participation or affection, nor as an accident. But of everything else as well, if it has a name, there will be a formula of what it means—that X belongs to Y; or instead of a simple formula one more exact—but no definition, nor essence. Or perhaps “definition,” like the “what,” has more than one sense. For the “what” in one sense means the substance and the individual, and in another each one of the categories: quantity, quality, etc. Just as “is” applies to everything, although not in the same way, but primarily to one thing and secondarily to others; so “what it is” applies in an unqualified sense to substance, and to other things in a qualified sense. For we might ask also what quality “is,” so that quality also is a “what it is”; not however without qualification, but just as in the case of not-being some say by a verbal quibble that not-being “is”—not in an unqualified sense, but “is” not-being—so too with quality. Now although we must also consider how we should express ourselves in each particular case, it is still more important to consider what the facts are. Hence now, since the language which we are using is clear, similarly essence also will belong primarily and simply to substance, and secondarily to other things as well; just as the “what it is” is not essence simply, but the essence of a quality or quantity. For it must be either by equivocation that we say that these things are , or by adding and subtracting qualifications, as we say that the unknowable is known¹⁵; since the truth is that we use the terms neither equivocally nor in the same sense, but just as we use the term “medical” in relation to one and the same thing; 1030bbut not of one and the same thing, nor yet equivocally. The term “medical” is applied to a body and a function and an instrument, neither equivocally nor in one sense, but in relation to one thing.¹⁶ However, in whichever way one chooses to speak of these things, it matters nothing; but this point is clear: that the primary and unqualified definition, and the essence, belong to substances. It is true that they belong equally to other things too, but not primarily . For if we assume this, it does not necessarily follow that there is a definition of anything which means the same as any formula; it must mean the same as a particular kind of formula, i.e. the formula of one thing— one not by continuity like the Iliad, or things which are arbitrarily combined, but in one of the proper senses of “one.” And “one” has the same variety of senses as “being.” “Being” means sometimes the individual thing, sometimes the quantity, sometimes the quality. Hence even “white man” will have a formula and definition; but in a different sense from the definition of “whiteness” and “substance.”