Now all these perceivable Essentiæ include Matter. The Substratum — Matter in one way — is Essence; while, in another way, the Form and the λόγος is Essence; and finally the Compound of the two is Essence. Matter is Hoc Aliquid, not ἐνεργείᾳ but only δυνάμει. Form is an Hoc Aliquid separable by reason (τῷ λόγῳ χωριστόν, p. 1042, a. 29). The Compound of the two, the complete Hoc Aliquid, is capable of existing separably, in an absolute sense (which is true also of some Forms), and is liable alone to generation and destruction (a. 30).
It is clear that Matter also, not less than Form, is Essence; for in all changes from opposite to opposite, there is a certain substratum to such changes. Thus, in changes of Place, there is a substratum which is now here, presently there; in changes of Quantity, what is now of such and such a size, is presently greater or less; in changes of Quality, what is now healthy is presently sick; in changes of Essence, what is now in course of generation is presently in course of destruction, or what is now the substratum of some given Form (and is thus Hoc Aliquid) is presently the substratum of Privation, and thus no longer Hoc Aliquid. Among these four varieties of change (κατ’ οὐσίαν, κατὰ ποσόν, κατὰ ποιόν, κατὰ τόπον) the three last are consequent upon the first, but the first is not consequent upon all the three last; for we cannot maintain that, because a thing has Matter capable of local movement, it must therefore have generable and destructible Matter (p. 1042, b. 6).
Having discussed the Essence of perceivable things so far forth as potential, we now proceed to the same Essence so far forth as actual (ἡ δυνάμει οὐσία — ἡ ὡς ἐνέργεια οὐσία τῶν αἰσθητῶν — p. 1042, b. 10). What is this last? Demokritus recognizes a primordial body one and the same as to Matter, but having three differences — in figure, in position, in arrangement. But it is plain that this enumeration is not sufficient and that there are many other differences, to each of which corresponds a special acceptation of ἔστι (τὸ ἔστι τοσαυταχῶς λέγεται — b. 26). Some differences depend upon the mode of putting together constituent materials (συνθέσει τῆς ὕλης — b. 16), as mixture, tying, gluing, pegging, &c.; some upon position, as threshold, coping, &c.; some upon time; some upon place; some upon affections of perceivable things, such as hardness, softness, dryness, moisture, density, rarity, &c.; some upon combinations of the foregoing; some again simply upon excess or defect in quantity. To one or other of these, ἔστιν has reference in each particular case. We say — This is a threshold, because it lies in a particular manner: Is (or To be — τὸ εἶναι) signifies in this case that particular manner of lying. To be ice, is to have become solidified in this particular manner (b. 28). We must therefore look for the summa genera of the differences; in some cases τὸ εἶναι will be defined by all these differences: thus more or less dense, more or less rare, belong to the genus excess and defect; differences of figure, smoothness, roughness, &c., belong to the genus straight and curve; in other cases, to be, or not to be, will depend upon mixture, as the genus (p. 1043, a. 1).
If then the Essence is the cause why each thing is what it is, we must seek in these differences the cause why each thing is what it is (p. 1043, a. 3). None of these differences indeed is itself Essence, — not even when it is embodied or combined with Matter; but it is in each the analogue of Essence, and must be employed in defining, just as in real and true Essence we define by predicating of Matter the Actuality or Formality (ὡς ἐν ταῖς οὐσίαις τὸ τῆς ὕλης κατηγορούμενον αὐτὴ ἡ ἐνέργεια — a. 6). Thus, if we define a threshold, we say — a piece of wood or stone lying in this particular way; if we define ice, we say — water frozen or solidified in this particular way, &c. The Form or Actuality of one Matter is different from that of another; so also is the rational explanation or Definition; in some cases it is composition, in others mixture, &c., and so forth. If any one defines a house by saying that it is stone or brick, he indicates only the potential house, for these are the Matter (a. 15); if he defines it — a vessel protecting bodies or property, he then assigns the Actuality (ἐνέργειαν); if he includes both of the above in his definition, he then gives the third Essence completed out of the two together (τὴν τρίτην καὶ τὴν ἐκ τούτων οὐσίαν — a. 18). To define from the differences, is to define from the side of the Actuality or Form; to define from the included elements (ἐκ τῶν ἐνυπαρχόντων) is to define from the side of the Matter (a. 20).
We see herefrom what perceivable Essence is, and how it is: partly, of the nature of Matter; partly, of Form and Actuality or Energy: again, the third or Concrete, out of both combined (p. 1043, a. 28). Sometimes, it is not clear whether the name signifies this third Concrete, or the Form and Energy. Thus, when you say a house, do you mean a protective receptacle built of bricks? or do you mean simply a protective receptacle — the Form simply, without specifying the Matter? When you say a line, do you mean a dyad in length — Form in Matter? or simply a dyad — Form alone? When you talk of an animal, do you mean soul in body? or simply soul, which is the Essence and Actuality of a certain body? The word animal may be applied to both, not indeed univocally, as implying generic resemblance, but (quasi-univocally, or semi-univocally) by analogical relationship to a common term (οὐχ ὡς ἑνὶ λόγῳ λεγόμενον, ἀλλ’ ὡς πρὸς ἓν — a. 36). This distinction however, though important in some respects, is unimportant so far as regards the investigation about perceivable Essence; for the τ.η.ε. belongs to the Form and the Actuality (a. 38). Soul, and the being soul, are identical; but man, and the being man, are not identical; unless the soul be called man. Thus this identity exists in some cases, but not in others (b. 4). A syllable is not composed merely of letters and synthesis, nor is a house simply of bricks and synthesis; for the synthesis or the mixture does not proceed out of the elements which are put together or mixed (b. 8). The like is true in other cases; e.g., if the threshold is a threshold by position, the position does not proceed out of the threshold, but rather the threshold out of the position. Nor again is man simply animal and biped. If these two are the Matter, there must be something apart from and beyond them, something not itself an element nor proceeding out of an element — the Essence; which is indicated by abstracting from the Matter (b. 13). This, as being the Cause of Existence and of Essence (αἴτιον τοῦ εἶναι καὶ τῆς οὐσίας — b. 14) is what is meant when Essence is spoken of.
This Essence or Form must be eternal; or at least, if destructible, it has never been destroyed; if generable, it has never been generated. For we have shown already that no one either constructs or generates Form: the Hoc Aliquid is constructed; the product of Form and Matter is generated (p. 1043, b. 18). As yet it has not been made clear whether the Essences of destructible things are separable or not: in some cases at least, they certainly are not — in those cases, namely, where there can exist nothing beyond the particular things, as a house or an implement (b. 21). Perhaps, indeed, these are not truly Essences — neither these particular things nor any other things which have come together not by natural process; for we might indicate Nature alone as the Essence in destructible things (τὴν γὰρ φύσιν μόνην ἄν τις θείη τὴν ἐν τοῖς φθαρτοῖς οὐσίαν) — b. 23. Aristotle seems to say in what precedes, that there is no γένεσις or φθορά of οὐσία; see Z. p. 1033, b. 17. But how is this to be reconciled with K. p. 1060, b. 18: οὐσίας μὲν γὰρ πάσης γένεσίς ἐστιν, στιγμῆς δ’ οὐκ ἔστιν? See Schwegler’s Comm. explaining γιγνόμενον and φθειρόμενον, Pt. II. pp. 82, 83).
Hence we see that the difficulty started by Antisthenes and others equally unschooled (ἀπαίδευτοι) is not without pertinence. They say that, as a definition is a sentence of many words, predicating something of something, so you cannot define Quid est: you can only define and inform persons Quale Quid est: you can only tell people what the definiend is like, not what it is in itself: you can tell them that silver is like tin, but you cannot tell what silver is. Upon this theory, definition may be given of Compound Essence, whether perceivable or cogitable; but not of the primordia of which the compound consists. The definition must predicate a something, which is of the nature of Form, of another something, which is of the nature of Matter (p. 1043, b. 31).
If Essences are (as the Platonists say) in a certain sense Numbers, they are so in this sense; not (as these philosophers affirm) in the character of assemblages of Monads. For the definition is a sort of number, divisible into indivisible units; and the number is so likewise. If you add any thing to, or deduct any thing from, a number (let the thing added or deducted be never so small), it will be no longer the same number; in like manner, neither the definition nor the τ.η.ε., will be the same, if any thing be added or subtracted (p. 1044, a. 1). Each number must have something which makes its component units coalesce into one number, though the Platonic philosophers cannot tell what that something is; either the units are a mere (uncemented) heap, or else you must say what is that something which makes them one out of many (a. 5). The definition also is one; yet these philosophers cannot explain what makes it one. The units of the number and that of the definition, is to be explained in the same way, and that of the Essence also; not as a monad or a point, but in each case like an Entelechy and a peculiar nature (οὐχ, ὡς λέγουσί τινες, οἷον μονάς τις οὖσα ἢ στιγμή, ἀλλ’ ἐντελέχεια καὶ φύσις τις ἑκάστη — a. 9). A given number admits of no degrees, more or less: neither does a given Essence, unless it be taken embodied in Matter (a. 10).
Respecting the Material Essence (περὶ δὲ τῆς ὑλικῆς οὐσίας — p. 1044, a. 15), we must not forget that, if there be one and the same First Matter common as a principle to all Generata or Fientia, there is nevertheless a certain Matter special or peculiar (proximate) to each (ὅμως ἔστι τις οἰκεία ἑκάστου — a. 18; οἰκεία καὶ προσεχής — Alexander). Thus the Materia Prima of phlegm is, sweet or fat things; that of bile is, bitter things and such like. Perhaps these two come both from the same Matter; and there are several different Matters of the same product, in cases where one Matter proceeds from another. Thus phlegm proceeds from fat and sweet, if fat proceeds from sweet; and even from bile, if bile be analysed into its First Matter from whence phlegm may proceed by a different road (a. 23). One thing may proceed from another in two different ways: either D may proceed from C, because C is its immediate Matter, already preformed up to a certain point, and thus on the way to a perfectly formed state; or D may proceed from C, after the destruction of C and the resolution of C into its Materia Prima (διχῶς γὰρ τόδ’ ἐκ τοῦδε, ἢ ὅτι πρὸ ὁδοῦ ἔσται ἢ ὅτι ἀναλυθέντος εἰς τὴν ἀρχήν — a. 24). From one and the same Matter different products may proceed, if the moving cause be different: from the same wood there may proceed a box or a bed. What product shall emerge does not, however, depend only upon the Moving Cause, but often upon the Matter also; thus a saw cannot be made out of wool or wood. If the same product can proceed out of different Matter, this is evidently because the Art or Moving Cause is the same: if this last be different, and the Matter different also, the product will of course be different (p. 1044, a. 32).