In this Book, Aristotle begins by recapitulating the doctrines and discussions of the preceding. His purpose had been declared to be the investigation of the Causes, Principles, and Elements of Essences. Now Essences are diverse: some universally admitted, as the natural elements and simple bodies, also plants, animals, and the parts of each, lastly, the heaven and the parts thereof; others not universally admitted, but advocated by some philosophers, as the Ideas and Mathematical Entia; others, again, which we arrive at by dialectical discussion, as t? t.?.e., the Substratum (Logical Entia — ?? t?? ?????, p. 1042, a. 12), the Genus more Essence than the Species, the Universal more Essence than Particulars. The (Platonic) Ideas make a near approach to the Genus and the Universal; they are vindicated as Essences upon similar grounds. Next, since t? t.?.e. is Essence, and since the Definition is the rational explanation of t.?.e., we found it necessary to discuss Definition; and, since the Definition is a sentence having parts, we were called upon to examine these parts, and to explain what parts belonged both to Essence and to Definition. We decided farther, after discussion, that the Universal and the Genus were not Essence; the Platonic Ideas and the Mathematical Entia we postponed for the moment, and we confined ourselves to the perceivable Essences, recognized by all (a. 25).

Now all these perceivable EssentiÆ include Matter. The Substratum — Matter in one way — is Essence; while, in another way, the Form and the ????? is Essence; and finally the Compound of the two is Essence. Matter is Hoc Aliquid, not ??e??e?? but only d???e?. Form is an Hoc Aliquid separable by reason (t? ???? ????st??, 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 (?at’ ??s?a?, ?at? p?s??, ?at? p????, ?at? t?p??) 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 (? d???e? ??s?a — ? ?? ?????e?a ??s?a t?? a?s??t?? — 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 ?st? (t? ?st? t?sa?ta??? ???eta? — b. 26). Some differences depend upon the mode of putting together constituent materials (s????se? t?? ???? — 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, ?st?? has reference in each particular case. We say — This is a threshold, because it lies in a particular manner: Is (or To be — t? e??a?) 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 t? e??a? 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 (?? ?? ta?? ??s?a?? t? t?? ???? ?at??????e??? a?t? ? ?????e?a — 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 (?????e?a?); if he includes both of the above in his definition, he then gives the third Essence completed out of the two together (t?? t??t?? ?a? t?? ?? t??t?? ??s?a? — a. 18). To define from the differences, is to define from the side of the Actuality or Form; to define from the included elements (?? t?? ???pa????t??) 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 (??? ?? ??? ???? ?e??e???, ???’ ?? p??? ?? — a. 36). This distinction however, though important in some respects, is unimportant so far as regards the investigation about perceivable Essence; for the t.?.e. 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 (a?t??? t?? e??a? ?a? t?? ??s?a? — 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 (t?? ??? f?s?? ???? ?? t?? ?e?? t?? ?? t??? f?a?t??? ??s?a?) — b. 23. Aristotle seems to say in what precedes, that there is no ???es?? or f???? of ??s?a; see Z. p. 1033, b. 17. But how is this to be reconciled with K. p. 1060, b. 18: ??s?a? ?? ??? p?s?? ???es?? ?st??, st???? d’ ??? ?st??? See Schwegler’s Comm. explaining ?????e??? and f?e???e???, Pt. II. pp. 82, 83).

Hence we see that the difficulty started by Antisthenes and others equally unschooled (?pa?de?t??) 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 t.?.e., 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 (???, ?? ?????s? t??e?, ???? ???? t?? ??sa ? st???, ???’ ??te???e?a ?a? f?s?? t?? ???st? — 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 (pe?? d? t?? ?????? ??s?a? — 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 (??? ?st? t?? ???e?a ???st?? — a. 18; ???e?a ?a? p??se??? — 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 (d???? ??? t?d’ ?? t??de, ? ?t? p?? ?d?? ?sta? ? ?t? ??a?????t?? e?? t?? ????? — 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).

When a man asks us, What is the Cause? we ought to reply, since the word has many senses, by specifying all the causes which can have a bearing on the case (p. 1044, a. 34). Thus, What is the Cause of man, as Matter? Perhaps the katamenia. What, as Movent? Perhaps the seed. What, as Form? The t.?.e. What, as ?? ??e?a? The End. These two last are perhaps both the same (a. 36). Moreover we ought to make answer by specifying the proximate causes (not the remote and ultimate). Thus, What is the Matter of man? We must answer by specifying the proximate matter; not fire and earth, the ultimate and elemental (b. 2).

This is the only right way of proceeding in regard to Essences natural and generable; since the Causes are many, and are what we seek to know. But the case is different in regard to Essences natural, yet eternal. Some of these last perhaps have no Matter at all; or at least a different Matter, having no attribute except local movability (b. 8. Alexander says in explanation: ???e? d? t?? ??pasa? t?? ??t? sfa???? ???da — ???? ?? ?e???t?? ?a? f?a?t?? ???? ???? ?at? t?p?? ????t?? — p. 527, 20-25, Bon.).

Again, in regard to circumstances which occur by Nature, but not in the way of Essence, there is no Matter at all: the subject itself is the Essence. Thus in regard to an eclipse: What is its Cause? What is its Matter? There is no Matter, except the moon which is affected in a certain way. What is the Cause, as Movent — here light-destroying? The earth. Perhaps there is no ?? ??e?a in the case. But the Cause in the way of Form is the rational explanation or definition; and this must include a specification of the Movent Cause, otherwise it will be obscure. Thus, the eclipse is, privation of light; and, when you add — by the earth intervening, you then specify the Movent, and make your definition satisfactory (b. 15).

In defining sleep we ought to say what part of the system is first affected thereby; but this is not clear. Shall we indicate only the animal (as substratum)? But this is not enough. We shall be asked, What part of the animal? Which part first? The heart, or what other part? Next, by what Cause? Lastly, how is the heart affected, apart from the rest of the system? To say — Sleep is a certain sort of immobility, will not be a sufficient definition. We must specify from what primary affection such immobility arises (p. 1044, b. 20).

Since some things exist, and do not exist, without generation or destruction (as Forms, and Points, if there be such things as Points), it is impossible that all Contraries can be generated out of each other, if every generation be both aliquid and ex aliquo. Albus homo ex nigro homine must be generated in a different way from album ex nigro. Now Matter is only to be found in those cases where there is generation and change into each other; in other cases, where no change takes place, there is no Matter. There is a difficulty in understanding how the Matter of each substance stands in regard to the contrary modifications of that substance (p. 1044, b. 29). If the body is potentially healthy, and if disease is the contrary of health, are we to say that both these states are potential? Is water potentially both wine and vinegar? Or are we to say rather that the body is the Matter of health, and that water is the Matter of wine, in the way of acquisition by nature and by taking on the Form to which it tends; and that the body is the Matter of sickness, and wine the Matter of vinegar in the way of privation and of destruction contrary to nature (b. 34)? However, there is here some difficulty: Since vinegar is generated out of wine, why is not wine the Matter of vinegar, and potentially vinegar? Why is not the living man potentially a corpse? Is it not rather the truth, however, that these are accidental or contra-natural destructions (?at? s?e???? a? f???a? — b. 36, i.e., not in the regular appetency and aspirations, according to which the destruction of one Form gives place to a better); and that through such destruction the same Matter which belonged to the living man becomes afterwards the Matter of the corpse; likewise the Matter of wine becomes, through the like destruction, Matter of vinegar — by a generation like that of night out of day? Changes of this sort must take place by complete resolution into the original Materia Prima (e?? t?? ???? de? ?pa?e??e?? — a. 3); thus, if a living animal comes out of a dead one, the latter is first resolved into its elements, and then out of them comes the living animal. So vinegar is first resolved into water, then out of the water comes wine (a. 5).

We shall now revert to the difficulty recently noticed, about Definitions and Numbers. What is the cause that each number and each definition is One? In all cases where there are several parts not put together as a mere heap, but where there is a Whole besides the parts, there must be some cause of this kind. With some bodies, contact is such cause; with others, viscosity (???s???t?? — p. 1045, a. 12), or some other affection. But the definition is one complex phrase, not by conjunction like the Iliad, but One by being the definition of one subject (a. 14). Now what is it which makes the subject man, One? Why is he One and not Many, say animal and a biped — more especially if there exist, as the Platonists say, a Self-animal and a Self-biped? Why are not these two a?t? the man (d?? t? ??? ??? ??e??a a?t? ? ?????p?? ?st?; — a. 17), so that individuals are men by participation not of one Self-man, but of the two — Self-animal, Self-biped? On this theory altogether, it would seem that a man cannot be One, but must be Many — animal and biped. It is plain that in this way of investigation the problem is insoluble.

But if, as we say (p. 1045, a. 23), there be on one side Matter, on the other side Form — on one side that which is in Potency, on the other side that which is in Act (a. 24) — the problem ceases to be difficult. The difficulty is the same as it would be if the definition of himation were, round brass: the word himation would be the sign of that definition, and the problem would be, What is the Cause why round and brass are One? But the difficulty vanishes, when we reply that one is Matter, the other Form. And, in cases where generation intervenes, what is the Cause why the potential Ens is actual Ens, except the Efficient (pa?? t? p???sa? — a. 31)? There is no other Cause why the sphere in potency is a sphere in actuality: such was the t.?.e. of each (t??t’ ?? t? t.?.e. ??at??? — a. 33). Of Matter there are two varieties, the Cogitable and the Perceivable; and, in the Definition, a part is always Matter, a part is Form or Energy; as when we define the circle — a plane figure. (Aristotle argues:— On the Platonic theory that Ideas or Forms are Entia, separate from particulars, self-existent, and independent of each other, no cause can be assigned for the coalescence of any two or more of them into one; e.g. animal and biped, into man. But upon my theory, Form and Matter, Power and Act, are in their own nature relative to each other. It is their own inherent nature to coalesce into one, or for Power to pass into Act. This is the cause of their unity: no other cause can be found or is necessary. See Alexander, p. 531.)

In those cases where there is no Matter, either cogitable or perceivable, as in the Categories, Hoc Aliquid, Quale, Quantum, &c., each of them is, in itself and at once, both Ens and Unum (p. 1045, b. 2). Hence neither Ens nor Unum is included in the Definitions, and the t.?.e. is, in itself and at once, both Ens and Unum. No other cause can be assigned why each of these is Ens and Unum; each of them is so, at once and immediately; yet not as if they were all included in Ens or Unum as common genera; nor as if they were apart and separable from particulars (b. 7).

Philosophers, who do not adopt this opinion, resort to various phrases, all unsatisfactory, to explain the coalescence or unity of the elements included in the Definition. Some call it ??e???, but they give no cause of the ??e???; others s????s?a, or s??des??, or s???es?? — of soul with body, as definition of life. But we might just as well use these phrases on other occasions, and say that to be well was a synthesis of the soul with health; that the brazen triangle was a s??des?? of brass with triangle; that white was a synthesis of superficies with whiteness (p. 1045, b. 15). These phrases carry no explanation; and these philosophers get into the difficulty by taking a wrong point of departure. They first lay down Power as different from Entelechy, and then look for an explanation which makes them one (a?t??? d’ ?t? d???e?? ?a? ??te?e?e?a? ??t??s? ????? ???p???? ?a? d?af???? — p. 1045, b. 16, Schwegler observes that the two last words are loosely put, and that the clear words to express what Aristotle means would be: ??t??s? ????? ???p???? ?p?t????te? d?af???? — Comm. II. p. 154.). But the truth is that Power and Entelechy are not essentially two, but only different aspects of one and the same. The Last Matter and the Form are the same; but the first is in potency, the second in perfect actuality (“Stoff und Form, Potenzielles und Actuelles, sind eins und dasselbe auf verschiedenen Entwicklungsstufen” — Schwegler II. p. 151). To enquire in any particular case what is the cause of this One, is the same as to enquire generally the cause of Unity. Each thing is a certain One; the Potential and the Actual are One, in a certain way (b. 20). So that no other Cause can be found except the Movent or Efficient — that which moved the matter out of Potency into Actuality. As to those things which have no Matter, each of them is One immediately and per se (b. 23).