Of beings, some subsist from nature, but others through other causes. From nature, indeed, animals subsist in their parts, together with plants and simple bodies such as earth and fire, air and water. For we say that these and things of this kind subsist from nature. But all the things we have enumerated appear to differ from those which do not consist from nature. For all such things as subsist from nature appear to contain in themselves a principle of motion and permanency; some according to place, others according to increase and diminution; and others according to changing quality. But a bed, a garment, and anything else of this kind, so far as they obtain these appellations, and so far as they are produced by art, have no innate impulse of mutation. So far, however, as it happens to them to be stony, or earthy, or mingled from these so far they possess this impulse; nature being as it were, a certain principle and cause of motion and rest, to that in which it is primarily inherent, essentially, and not according to accident. I say, “not according to accident”, because a man made the cause of health to himself in consequence of being a physician; at the same time, however, he possesses medicine, not so far as he is made well; but it happens that the same person is a physician, and acquires health. Hence, these are sometimes separated from each other. In a similar manner, everything else which is made subsists; for none of them contains in itself the principle of making; but some of them have this principle in other things, and external to themselves as a house, and everything else which is made by the hand; and others have it in themselves, indeed, yet not essentially, viz., such things as are causes to themselves from accident. Such, therefore, is nature. But those things possess nature which contain a principle of this kind. And all these are essences (or substances); for nature is always a certain subject, and is in a subject. These things, too, are said to subsist according to nature, and such as are essentially inherent in these. Thus, for instance, fire tends upwards, according to nature; for this property is not nature, nor does it possess nature, but is by nature, and according to nature. What nature, therefore is, has been said, and also what a subsistence is, by and according to nature.
But to attempt to demonstrate that nature is, would be ridiculous: for it is evident that there are many beings of this kind: and to demonstrate things apparent through such as are unapparent, is the province of one who is incapable of judging what is essentially, and what is not essentially known. That some, however, may be less affected is not immanifest: for one who has blind from his birth may reason about colors. So that men of this kind must necessarily discourse about names, but understand nothing of the subject of their discourse. But to some, nature, and the essence of things which subsist from nature, appears to be that which is first inherent in every thing, and which is essentially destitute of order and ornament. Thus, for instance, wood is the nature of a bed, and brass of a statue; of which, according to Antiphon, this is a token that if someone should bury a bed, and the rottenness should receive a germinating power, a bed would not be generated, but wood; as if the disposition, which is according to rhythm and art, were inherent from accident, but the essence that which remains, and which to these things is continually passive. If also each of these is affected after the very same manner towards something else—as, for instance, brass and gold towards water, but bones and wood towards earth, and in like manner anything else, these things, he says, are their nature and essence. Hence, by some, earth—by others, fire—by others, air and by others, water—is said to be the nature of things. And by others this is asserted of some, and by others again of all of these. For that which some one of these apprehends to be a thing of a certain quality, whether it be one or many, this, and so many, they say is every essence: for all other things are the passions, habits, and dispositions of these. They also asserted that any one of these, whatever, is perpetual, because no change is produced in them from themselves; but that other things are infinitely generated and corrupted. According to one mode, therefore, nature is thus denominated, viz., the first subject matter to everything which contains in itself the principle of motion and mutation. But after another mode it is denominated form, which subsists according to definition: for as art is called that which subsists according to art, and that which is artificial; so likewise nature is both called that which is according to nature and that which is natural. Nor must we say that anything, for instance, a bed, posseses a subsistence, according to art; if it is a bed only in capacity, and has not yet the form of a bed; nor must we say that it is art. Neither in things which consist from nature must this be asserted; for that which is flesh or bone in capacity does not yet possess its proper nature until it receives form according to definition; by defining which, we say what flesh is, or bone. Nor does it subsist by nature: so that the nature of things which contain in themselves a principle of motion, will be after another manner, morphe and form, which are not separate except according to definition. But that which is composed from these is not nature, but consists from nature; as, for instance, man. And this is nature in a greater degree than matter: for everything is then said to be, when it is formed in energy (entelecheia), rather than when it is in capacity.
Farther still: man is generated from man, but a bed is not generated from a bed. Hence, they say that not the figure but the wood is nature; because if it should germinate, it would not become a bed, but wood. If, therefore, this is art, form also is nature; for man is generated from man. Again, nature considered as generation, is a path to nature: for it does not subsist in the same manner as healing, which is said to be a path not to medicine but to health; since it is necessary that healing should be procured from medicine, and not lead to medicine. Nature, however, does not thus subsist with respect to nature; but that which is born proceeds or takes its beginning from something to something. To what, then, does it proceed? Not to that from which, but to that to which. Form, therefore, is nature. But form in nature are predicated in a twofold respect; for privation also is in a certain respect form. Whether, however, privation and something contrary, do or do not subsist about simple generation, will be considered hereafter.
