Now there are three Essences. The Perceivable includes two varieties: one, the Perishable, acknowledged by all, e.g., animals and plants; the other Eternal, of which we must determine the elements, be they many or one. There is also the Immoveable, which some consider to be separable (ἄλλη δὲ ἀκίνητος καὶ ταύτην τινὲς εἶναι φασι χωριστήν — p. 1069, a. 33; οὐσία νοητὴ καὶ ἀκίνητος — Schwegler’s note): either recognizing two varieties thereof, distinct from each other — the Forms and Mathematical Entia; or not recognizing Forms as separable Entia, but only the Mathematical Entia (a. 36). Now the first, or Perceivable Essences, belong to physical science, since they are moveable or endued with motion; the Immoveable Essences, whether there be two varieties of them or only one, belong to a science distinct from physical. The Perceivable and the Immoveable Essences have no common principles (b. 2).
The Perceivable Essence is subject to change (μεταβλητή). Since change takes place either out of Opposites or out of Intermediates, and not out of every variety of Opposites, but only out of Contraries (ἐκ τῆς οἰκείας ἀποφάσεως, ἐκ τῆς οἰκείας στερήσεως — Alexander, pp. 644, 645, Bon.; the voice, e.g., is not white, yet change does not take place from voice to white, these being disparates, or of different genera: τὰ γένει διαφέροντα οὐκ ἔχει ὁδὸν εἰς ἄλληλα — I. iv. p. 1055, a. 6), there must of necessity be a certain Substratum which changes into the contrary condition; for contraries do not change into each other. The substratum remains, but the contraries do not remain: there is therefore a third something besides the contraries; and that is Matter (p. 1069, b. 9). Since then the varieties of change are four: (1) γένεσις and φθορά (κατὰ τὸ τί), (2) αὔξησις καὶ φθίσις (κατὰ τὸ ποσόν), (3) ἀλλοίωσις (κατὰ τὸ πάθος or κατὰ τὸ ποιόν), (4) φορά (κατὰ τόπον or κατὰ τὸ ποῦ), each of these changes will take place into its respective contrary: the Matter will necessarily change, having the potentiality of both contraries (b. 14). Ens being two-fold, all change takes place out of Ens Potentiâ into Ens Actu, e.g., out of potential white into actual white; and the like holds for Increase and Decrease. Thus not only may there be generation from Non-Ens accidentally but all generation takes place also out of Ens; that is, out of Ens Potentiâ, not Ens Actu (b. 20). This Ens Potentiâ is what Anaxagoras really means by his Unum, which is a better phrase than ὁμοῦ πάντα; what Empedokles and Anaxagoras mean by their μῖγμα; what Demokritus means when he says ὁμοῦ πάντα. They mean that all things existed at once potentially, though not actually; and we see that these philosophers got partial hold of the idea of Matter (ὥστε τῆς ὕλης ἂν εἶεν ἡμμένοι — b. 24). All things subject to change possess Matter, but each of them a different Matter; even the eternal things which are not generated but moved in place, possess Matter — not generated, but from whence whither (i.e., the Matter of local movement pure and simple — direction: καὶ τῶν ἀϊδίων ὅσα μὴ γεννητὰ κινητὰ δὲ φορᾷ, ἀλλ’ οὐ γεννητήν (ὕλην), ἀλλὰ πόθεν ποῖ — b. 26).
Since there are three varieties of Non-Ens (p. 1069, b. 27; Alexander and Bonitz explain this τριχῶς differently), it may seem difficult to determine, out of which among the three Generation takes place. But the answer is, that the Potential Ens is not potential of every thing alike and at haphazard, but potential in each case from something towards something (εἰ δὴ τί ἐστι δυνάμει, ἀλλ’ ὅμως οὐ τοῦ τυχόντος, ἀλλ’ ἕτερον ἐξ ἑτέρου — b. 29). Nor is it enough to tell us that all things are huddled together (ὁμοῦ πάντα χρήματα — b. 30); for they differ in respect to Matter or Potentiality. If this were not so, how is it that they are of infinite diversity, and not all One? The Noûs (i.e., according to the theory of Anaxagoras) is One; so that, if the Matter were One also, it would become in actuality that which it was at first in potentiality, and the result would be all One and the Same (b. 32).
The Causes are thus three and the Principles are three: the pair of Contraries, one of them Form (λόγος καὶ εἶδος), the other Privation, and the third Matter (p. 1069, b. 35). But we must keep in mind that neither Materia Prima nor Forma Prima is generated. For in all Change, there is something (the Matter) which undergoes change; something by which the change is effected (the Prime Movent, ὑφ’ οὗ μέν, τοῦ πρώτου κινοῦντος — p. 1070, a. 1); and something into which the change takes place (the Form). The brass becomes round; but, if both the brass becomes and the round becomes, you will be condemned to an infinite regression: you must stop somewhere (ἀνάγκη δὴ στῆναι — a. 4). Moreover, every Essentia is generated out of another Essentia of the same name and form (ἐκ συνωνύμου — a. 5). All generated things proceed either from Nature, Art, Fortune, or Spontaneity. It is Nature, where the principle or beginning is in the subject itself; it is Art, where the principle or beginning is in something apart from the subject; Fortune is the privation of Art; Spontaneity is the privation of Nature (αἱ δὲ λοιπαὶ αἴτιαι στερήσεις τούτων — a. 9). Essentiæ are threefold: (1) Matter, which appears to be Hoc Aliquid but is not so, for detached members or fragments, simply touching each other without coalescing, are matter and substratum (i.e., prepared for something ulterior); (2) Nature, which is really Hoc Aliquid — a certain definite condition, into which generation takes place (ἡ δὲ φύσις καὶ τόδε τι, εἰς ἥν, καὶ ἕξις τις — a. 12); (3) The Concrete of the two preceding — the individual object called Sokrates or Kallias. In some cases there is no Hoc Aliquid except in this Concrete or Compound; thus in artificial objects or productions, such as a house or health, there is no Form except the Art itself: the ideal house, pre-existing in the mind of the builder, is generated and destroyed in a different sense from the real house. It is in the case of natural objects, if in any case, that there exists a Hoc Aliquid independent of the concrete individual (a. 17).
Hence Plato was not wrong in saying that Forms were coextensive with natural objects (ὁπόσα φύσει — p. 1070, a. 18), if there are Forms distinct from these objects: such as fire, flesh, head, which are all properly Matter. The Last Matter (or that which has come most under the influence of Form) belongs to that which is in the fullest sense Essentia (or the individual concrete named Sokrates or Kallias — a. 20). The Moving Causes pre-exist, as real individual beings or objects: the Formal Causes come into existence simultaneously with the individual real compound. When the patient becomes well, then health comes at the same time into existence: when the brazen sphere comes, the sphericity of it comes at the same time (a. 24). Whether any thing of the Form continues after the dissolution of the individual compound, is a problem to be investigated (a. 25). In some cases nothing hinders but what it may continue; for example, the soul may be of such a nature: I do not mean every soul — for every soul perhaps cannot continue — but the Νοῦς or rational soul (a. 27). Still it is plain that this affords no support to the theory of self-existent separate Ideas; for every individual man is begotten by another individual man. In like manner also with respect to the arts; for the medical art affords the Form or rational explanation of health (a. 30; i.e., health is generated, not by the Idea of Health, but by the medical art, or by the artist in whom that art is embodied).
Causes and principles, in one point of view, are different: different subjects; but in another point of view, they are the same for all; that is, if we speak generally and according to analogy (if we confine ourselves to the most general terms, Form, Privation, Matter, &c.). In respect to Essentia, Relatio, and the remainder of the Categories, a difficulty arises to say whether the causes, elements, and principles of all the Categories are the same. It would be strange if they were all the same; because then Essentiæ, as well as Relata, would proceed out of the same causes and elements. For, what can these latter be? They cannot be extra-categorical; since there exists no general class apart from or besides Essentia and the other Categories (p. 1070, b. 1). Nor can any one Category be the element of the others: for the element is prius to that of which it is the element. Nor again can Essentia be the element of Relata; nor is any one of the nine Categories the element of Essentia. Again, how is it possible that the elements of all the Categories can be the same? No element can be the same as that compound of which it is an element: neither B nor A can be the same as B A. If, therefore, there were such elements, they must be extra-categorical; which is impossible. Nor can the element in question (the supposed one and the same) be any cogitable, such as Ens or Unum; for every individual Concrete is both Ens and Unum and the element cannot be identical with the compound put together out of it. Neither Essentia nor Relatio could be said to exist, if Ens were the element out of which they are composed; but these Categories exist necessarily: therefore there is no one and the same element common to all the Categories (b. 9).
Yet we ought perhaps rather to repeat, what was observed before, that in one sense, the elements of all are the same; in another sense, different. Take for example the perceivable bodies. We find here hot as the Form, cold as the Privation; as Matter, there is that which is, primarily and per se, both hot and cold potentially: the hot and the cold are both Essentiæ; likewise other things of which these are the principles, e.g., flesh and bone, which of necessity are different from the principles out of which they proceed (b. 15). Flesh and bone have these elements and principles; other things have other elements and principles. The same specific principles cannot be assigned to all, but only principles analogous to these in each case, as saying, in general terms, that there are three principles — Form, Privation, Matter. Each of these is different in every different genus; thus in colour, the principles are white, black, surface, light, darkness, air, and out of these are generated day and night (b. 21).
The three preceding causes are all intrinsic or immanent (ἐνυπάρχοντα). But there are other causes also extrinsic, such as the Movent. So that Principle and Element are not exactly identical; for Principle as well as Cause includes all the four: τὸ κινοῦν ἢ ἱστάν is a Principle, and is itself an Essentia (p. 1070, b. 25). Thus the analogous Elements are three, while the Principles or Causes are four; but the four are specifically different in each different case. Thus, health is Form; sickness is Privation; body is Matter; the medical art is Movent. House is Form; disorder of a certain sort is Privation; bricks are Matter; the building art is Movent. We thus make out four Causes; yet, in a certain sense, there will be only three (b. 32). For, in natural products, a man is the Movent Cause of a man; in artificial products (ἐν τοῖς ἀπὸ διανοίας) the Movent is Form or Privation. In a certain sense, the medical art is health, and the building art is the Form of a house, and a man begets a man. And farther, over and above these special movent causes, there is the Primum Movens of all (b. 35).
We distinguish what is separable from what is not separable. Now Essentiæ, and they only, are separable; accordingly they are the causes of every thing else, since without Essentiæ there cannot be either affections or movements (p. 1071, a. 2). Such causes would be soul and body, or reason, appetite, and body. Again, in another sense, the principles of all things are generically the same, though specifically different; such are Potentia and Actus. In some cases, the same thing exists now potentially, at another time actually; thus wine, though actually wine, is potentially vinegar; flesh is actually flesh, potentially a man, Potentia and Actus will merge in the above-mentioned causes — Form, Privation, Matter, Movent (a. 7). For the Form (if it be separable), the Concrete (of Form and Matter), and Privation (like darkness or sickness) — all these exist actually; while Matter exists potentially, capable either of Form or Privation. Things differ potentially and actually sometimes through difference in the Matter, sometime through difference in the Form. Thus, the cause of a man is, in the way of Matter, the elements fire and earth; in the way of Form his own Form, and the same Form in another individual — his father and besides these, the Sun with its oblique motion; which last neither Matter, nor Form, nor Privation, nor the like Form in another individual, but a Movent Cause (ἀλλὰ κινοῦντα — a. 17).
We must remember, besides, that some things may be described in general terms, others cannot be so described. The first principles of all things are, speaking in general terms, Hoc Primum Actu and Aliud Primum Potentiâ. These universals do not really exist (p. 1071, a. 19), for the principium of all individuals is some other individual. Man indeed is the principium of the Universal Man but no Universal Man exists (a. 21). Peleus is the principium of Achilles; your father, of you; this B, of that B A; B, the universal, of B A the universal. Next (after the Movent) come the Forms of Essences; but the different genera thereof (as has been already stated), colours, sounds, essences, quantities, &c., have different causes and elements, though the same when described in general terms and by analogy; also different individuals in the same species have different causes and elements, not indeed different in species, but different individually; that is, your Matter, your Movent, your Form, are different from mine, though in general terms and definition they are the same (τῷ καθόλου δὲ λόγῳ ταὐτά â€” a. 29).