The question arises: If one denies that a formula involving an added determinant is a definition, how can there be a definition of terms which are not simple but coupled? Because they can only be explained by adding a determinant. I mean, e.g., there is “nose” and “concavity” and “snubness,” the term compounded of the two, because the one is present in the other. Neither “concavity” nor “snubness” is an accidental, but a per se affection of the nose.¹ Nor are they attributes in the sense that “white” is of Callias or a man, because Callias is white and is by accident a man; but in the sense that “male” is an attribute of animal, and equality of quantity, and all other attributes which we say belong per se. That is, all things which involve the formula or name of the subject of the affection, and cannot be explained apart from it. Thus “white” can be explained apart from “man,” but not “female” apart from “animal.” Thus either these terms have no essence or definition, or else they have it in a different sense, as we have said. But there is also another difficulty about them. If “snub nose” is the same as “concave nose,” “snub” will be the same as “concave.” But if not, since it is impossible to speak of “snub” apart from the thing of which it is a per se affection (because “snub” means a concavity in the nose), either it is impossible to call the nose snub, or it will be a tautology, “concave-nose nose” because “snub nose” will equal “concave-nose nose.” Hence it is absurd that such terms as these should have an essence. Otherwise there will be an infinite regression; for in “snub-nose nose” there will be yet another nose. 1031aClearly, then, there is definition of substance alone. If there were definition of the other categories also, it would have to involve an added determinant, as in the case of the qualitative; and of the odd, for this cannot be defined apart from number; nor can “female” apart from “animal.” By “involving an added determinant” I mean descriptions which involve a tautology, as in the above examples. Now if this is true, there will be no definition of compound expressions either; e.g., “odd number.” We fail to realize this because our terms are not used accurately. If on the other hand there are definitions of these too, either they are defined in a different way, or, as we have said, “definition” and “essence” must be used in more than one sense; thus in one sense there will be no definition of anything, and nothing will have an essence, except substances; and in another those other things will have a definition and essence. It is obvious, then, that the definition is the formula of the essence, and that the essence belongs either only to substances, or especially and primarily and simply.

We must inquire whether the essence is the same as the particular thing, or different. This is useful for our inquiry about substance; because a particular thing is considered to be nothing other than its own substance, and the essence is called the substance of the thing. In accidental predications, indeed, the thing itself would seem to be different from its essence; e.g., “white man” is different from “essence of white man.” If it were the same, “essence of man” and “essence of white man” would be the same. For “man” and “white man” are the same, they say, and therefore “essence of white man” is the same as “essence of man.” But perhaps it is not necessarily true that the essence of accidental combinations is the same as that of the simple terms; because the extremes of the syllogism are not identical with the middle term in the same way.² Perhaps it might be thought to follow that the accidental extremes are identical; e.g. “essence of white” and “essence of cultured”; but this is not admitted.³ But in per se expressions, is the thing necessarily the same as its essence, e.g., if there are substances which have no other substances or entities prior to them, such as some hold the Ideas to be? For if the Ideal Good is to be different from the essence of good, and the Ideal Animal and Being from the essence of animal and being, 1031bthere will be other substances and entities and Ideas besides the ones which they describe; and prior to them, if essence is substance. And if they are separate from each other, there will be no knowledge of the Ideas, and the essences will not exist (by “being separate” I mean if neither the essence of good is present in the Ideal Good, nor “being good” in the essence of good); for it is when we know the essence of it that we have knowledge of a thing. And it is the same with other essences as with the essence of good; so that if the essence of good is not good, neither will the essence of being “be,” nor the essence of one be one. Either all essences exist alike, or none of them; and so if not even the essence of being “is,” neither will any other essence exist. Again that to which “essentially good” does not apply cannot be good. Hence “the good” must be one with the essence of good, “the beautiful” with the essence of beauty, and so with all terms which are not dependent upon something else, but self-subsistent and primary.⁴ For it is enough if this is so, even if they are not Forms; or perhaps rather even if they are. (At the same time it is clear also that if the Ideas are such as some hold, the substrate will not be substance; for the Ideas must be substances, but not involving a substrate, because if they did involve one they would exist in virtue of its participation in them.)⁵ That each individual thing is one and the same with its essence, and not merely accidentally so, is apparent, not only from the foregoing considerations, but because to have knowledge of the individual is to have knowledge of its essence; so that by setting out examples it is evident that both must be identical. But as for the accidental term, e.g. “cultured” or “white,” since it has two meanings, it is not true to say that the term itself is the same as its essence; for both the accidental term and that of which it is an accident are “white,” so that in one sense the essence and the term itself are the same, and in another they are not, because the essence is not the same as “the man” or “the white man,” but it is the same as the affection. The absurdity 〈of separating a thing from its essence〉 will be apparent also if one supplies a name for each essence; for then there will be another essence besides the original one, e.g. the essence of “horse” will have a further essence. Yet why should not some things be identified with their essence from the outset,⁶ if essence is substance? Indeed not only are the thing and its essence one, but their formula is the same, 1032aas is clear from what we have just stated; for it is not by accident that the essence of “one,” and “the one,” are one. Moreover, if they are different, there will be an infinite series; for the essence of “one” and “the one” will both exist; so that in that case too the same principle will apply.⁷ Clearly, then, in the case of primary and self-subsistent terms, the individual thing and its essence are one and the same. It is obvious that the sophistical objections to this thesis are met in the same way as the question whether Socrates is the same as the essence of Socrates; for there is no difference either in the grounds for asking the question or in the means of meeting it successfully. We have now explained in what sense the essence is, and in what sense it is not, the same as the individual thing.

Of things which are generated, some are generated naturally, others artificially, and others spontaneously; but everything which is generated is generated by something and from something and becomes something. When I say “becomes something” I mean in any of the categories; it may come to be either a particular thing or of some quantity or quality or in some place. Natural generation is the generation of things whose generation is by nature. That from which they are generated is what we call matter; that by which, is something which exists naturally; and that which they become is a man or a plant or something else of this kind, which we call substance in the highest degree. All things which are generated naturally or artificially have matter; for it is possible for each one of them both to be and not to be, and this possibility is the matter in each individual thing. And in general both that from which and that in accordance with which they are generated, is nature; for the thing generated, e.g. plant or animal, has a nature. And that by which they are generated is the so-called “formal” nature, which has the same form as the thing generated (although it is in something else); for man begets man. Such is the generation of things which are naturally generated; the other kinds of generation are called productions. All productions proceed from either art or potency or thought. Some of them are also generated spontaneously and by chance in much the same way as things which are naturally generated; for sometimes even in the sphere of nature the same things are generated both from seed and without it.⁸ We shall consider cases of this kind later.⁹ 1032bThings are generated artificially whose form is contained in the soul (by “form” I mean the essence of each thing, and its primary substance); for even contraries have in a sense the same form.¹⁰ For the substance of the privation is the opposite substance; e.g., health is the substance of disease; for disease is the absence of health, and health is the formula and knowledge in the soul. Now the healthy subject is produced as the result of this reasoning: since health is so-and-so, if the subject is to be healthy, it must have such-and-such a quality, e.g. homogeneity; and if so, it must have heat. And the physician continues reasoning until he arrives at what he himself finally can do; then the process from this point onwards, i.e. the process towards health, is called “production.” Therefore it follows in a sense that health comes from health and a house from a house; that which has matter from that which has not (for the art of medicine or of building is the form of health or the house). By substance without matter I mean the essence. In generations and motions part of the process is called cogitation, and part production—that which proceeds from the starting-point and the form is cogitation, and that which proceeds from the conclusion of the cogitation is production. Each of the other intermediate measures is carried out in the same way. I mean, e.g., that if A is to be healthy, his physical condition will have to be made uniform. What, then, does being made uniform entail? So-and-so; and this will be achieved if he is made hot. What does this entail? So-and-so; now this is potentially present, and the thing is now in his power. The thing which produces, and from which the process of recovering health begins, is the form in the soul, if the process is artificial; if spontaneous, it is whatever is the starting-point of the production for the artificial producer; as in medical treatment the starting-point is, perhaps, the heating of the patient; and this the doctor produces by friction. Heat in the body, then, is either a part of health, or is followed (directly or through several intermediaries) by something similar which is a part of health. This is the ultimate thing, namely that produces, and in this sense is a part of, health—or of the house (in the form of stones)¹¹ or of other things. Therefore, as we say, generation would be impossible if nothing were already existent. It is clear, then, that some part must necessarily pre-exist; because the matter is a part, since it is matter which pre-exists in the product and becomes something. 1033aBut then is matter part of the formula? Well, we define bronze circles in both ways; we describe the matter as bronze, and the form as such-and-such a shape; and this shape is the proximate genus in which the circle is placed. The bronze circle, then, has its matter in its formula. Now as for that from which, as matter, things are generated, some things when they are generated are called not “so-and-so,” but “made of so-and-so”; e.g., a statue is not called stone, but made of stone. But the man who becomes healthy is not called after that from which he becomes healthy. This is because the generation proceeds from the privation and the substrate, which we call matter (e.g., both “the man” and “the invalid” become healthy), but it is more properly said to proceed from the privation; e.g., a man becomes healthy from being an invalid rather than from being a man. Hence a healthy person is not called an invalid, but a man, and a healthy man. But where the privation is obscure and has no name—e.g. in bronze the privation of any given shape, or in bricks and wood the privation of the shape of a house—the generation is considered to proceed from these materials, as in the former case from the invalid. Hence just as in the former case the subject is not called that from which it is generated, so in this case the statue is not called wood, but is called by a verbal change not wood, but wooden; not bronze, but made of bronze; not stone, but made of stone; and the house is called not bricks, but made of bricks. For if we consider the matter carefully, we should not even say without qualification that a statue is generated from wood, or a house from bricks; because that from which a thing is generated should not persist, but be changed. This, then, is why we speak in this way.