by Aristotle
   attribute-plainly, I say, everything comes to be from both subject and
   form. For 'musical man' is composed (in a way) of 'man' and 'musical':
   you can analyse it into the definitions of its elements. It is clear
   then that what comes to be will come to be from these elements.
   Now the subject is one numerically, though it is two in form. (For
   it is the man, the gold-the 'matter' generally-that is counted, for it
   is more of the nature of a 'this', and what comes to be does not
   come from it in virtue of a concomitant attribute; the privation, on
   the other hand, and the contrary are incidental in the process.) And
   the positive form is one-the order, the acquired art of music, or
   any similar predicate.
   There is a sense, therefore, in which we must declare the principles
   to be two, and a sense in which they are three; a sense in which the
   contraries are the principles-say for example the musical and the
   unmusical, the hot and the cold, the tuned and the untuned-and a sense
   in which they are not, since it is impossible for the contraries to be
   acted on by each other. But this difficulty also is solved by the fact
   that the substratum is different from the contraries, for it is itself
   not a contrary. The principles therefore are, in a way, not more in
   number than the contraries, but as it were two, nor yet precisely two,
   since there is a difference of essential nature, but three. For 'to be
   man' is different from 'to be unmusical', and 'to be unformed' from
   'to be bronze'.
   We have now stated the number of the principles of natural objects
   which are subject to generation, and how the number is reached: and it
   is clear that there must be a substratum for the contraries, and
   that the contraries must be two. (Yet in another way of putting it
   this is not necessary, as one of the contraries will serve to effect
   the change by its successive absence and presence.)
   The underlying nature is an object of scientific knowledge, by an
   analogy. For as the bronze is to the statue, the wood to the bed, or
   the matter and the formless before receiving form to any thing which
   has form, so is the underlying nature to substance, i.e. the 'this' or
   existent.
   This then is one principle (though not one or existent in the same
   sense as the 'this'), and the definition was one as we agreed; then
   further there is its contrary, the privation. In what sense these
   are two, and in what sense more, has been stated above. Briefly, we
   explained first that only the contraries were principles, and later
   that a substratum was indispensable, and that the principles were
   three; our last statement has elucidated the difference between the
   contraries, the mutual relation of the principles, and the nature of
   the substratum. Whether the form or the substratum is the essential
   nature of a physical object is not yet clear. But that the
   principles are three, and in what sense, and the way in which each
   is a principle, is clear.
   So much then for the question of the number and the nature of the
   principles.
   8
   We will now proceed to show that the difficulty of the early
   thinkers, as well as our own, is solved in this way alone.
   The first of those who studied science were misled in their search
   for truth and the nature of things by their inexperience, which as
   it were thrust them into another path. So they say that none of the
   things that are either comes to be or passes out of existence, because
   what comes to be must do so either from what is or from what is not,
   both of which are impossible. For what is cannot come to be (because
   it is already), and from what is not nothing could have come to be
   (because something must be present as a substratum). So too they
   exaggerated the consequence of this, and went so far as to deny even
   the existence of a plurality of things, maintaining that only Being
   itself is. Such then was their opinion, and such the reason for its
   adoption.
   Our explanation on the other hand is that the phrases 'something
   comes to be from what is or from what is not', 'what is not or what is
   does something or has something done to it or becomes some
   particular thing', are to be taken (in the first way of putting our
   explanation) in the same sense as 'a doctor does something or has
   something done to him', 'is or becomes something from being a doctor.'
   These expressions may be taken in two senses, and so too, clearly, may
   'from being', and 'being acts or is acted on'. A doctor builds a
   house, not qua doctor, but qua housebuilder, and turns gray, not qua
   doctor, but qua dark-haired. On the other hand he doctors or fails
   to doctor qua doctor. But we are using words most appropriately when
   we say that a doctor does something or undergoes something, or becomes
   something from being a doctor, if he does, undergoes, or becomes qua
   doctor. Clearly then also 'to come to be so-and-so from not-being'
   means 'qua not-being'.
   It was through failure to make this distinction that those
   thinkers gave the matter up, and through this error that they went
   so much farther astray as to suppose that nothing else comes to be
   or exists apart from Being itself, thus doing away with all becoming.
   We ourselves are in agreement with them in holding that nothing
   can be said without qualification to come from what is not. But
   nevertheless we maintain that a thing may 'come to be from what is
   not'-that is, in a qualified sense. For a thing comes to be from the
   privation, which in its own nature is not-being,-this not surviving as
   a constituent of the result. Yet this causes surprise, and it is
   thought impossible that something should come to be in the way
   described from what is not.
   In the same way we maintain that nothing comes to be from being, and
   that being does not come to be except in a qualified sense. In that
   way, however, it does, just as animal might come to be from animal,
   and an animal of a certain kind from an animal of a certain kind.
   Thus, suppose a dog to come to be from a horse. The dog would then, it
   is true, come to be from animal (as well as from an animal of a
   certain kind) but not as animal, for that is already there. But if
   anything is to become an animal, not in a qualified sense, it will not
   be from animal: and if being, not from being-nor from not-being
   either, for it has been explained that by 'from not being' we mean
   from not-being qua not-being.
   Note further that we do not subvert the principle that everything
   either is or is not.
   This then is one way of solving the difficulty. Another consists
   in pointing out that the same things can be explained in terms of
   potentiality and actuality. But this has been done with greater
   precision elsewhere. So, as we said, the difficulties which
   constrain people to deny the existence of some of the things we
   mentioned are now solved. For it was this reason which also caused
   some of the earlier thinkers to turn so far aside from the road
   which leads to coming to be and passing aw
ay and change generally.
   If they had come in sight of this nature, all their ignorance would
   have been dispelled.
   9
   Others, indeed, have apprehended the nature in question, but not
   adequately.
   In the first place they allow that a thing may come to be without
   qualification from not being, accepting on this point the statement of
   Parmenides. Secondly, they think that if the substratum is one
   numerically, it must have also only a single potentiality-which is a
   very different thing.
   Now we distinguish matter and privation, and hold that one of these,
   namely the matter, is not-being only in virtue of an attribute which
   it has, while the privation in its own nature is not-being; and that
   the matter is nearly, in a sense is, substance, while the privation in
   no sense is. They, on the other hand, identify their Great and Small
   alike with not being, and that whether they are taken together as
   one or separately. Their triad is therefore of quite a different
   kind from ours. For they got so far as to see that there must be
   some underlying nature, but they make it one-for even if one
   philosopher makes a dyad of it, which he calls Great and Small, the
   effect is the same, for he overlooked the other nature. For the one
   which persists is a joint cause, with the form, of what comes to
   be-a mother, as it were. But the negative part of the contrariety
   may often seem, if you concentrate your attention on it as an evil
   agent, not to exist at all.
   For admitting with them that there is something divine, good, and
   desirable, we hold that there are two other principles, the one
   contrary to it, the other such as of its own nature to desire and
   yearn for it. But the consequence of their view is that the contrary
   desires its wtextinction. Yet the form cannot desire itself, for it is
   not defective; nor can the contrary desire it, for contraries are
   mutually destructive. The truth is that what desires the form is
   matter, as the female desires the male and the ugly the beautiful-only
   the ugly or the female not per se but per accidens.
   The matter comes to be and ceases to be in one sense, while in
   another it does not. As that which contains the privation, it ceases
   to be in its own nature, for what ceases to be-the privation-is
   contained within it. But as potentiality it does not cease to be in
   its own nature, but is necessarily outside the sphere of becoming
   and ceasing to be. For if it came to be, something must have existed
   as a primary substratum from which it should come and which should
   persist in it; but this is its own special nature, so that it will
   be before coming to be. (For my definition of matter is just
   this-the primary substratum of each thing, from which it comes to be
   without qualification, and which persists in the result.) And if it
   ceases to be it will pass into that at the last, so it will have
   ceased to be before ceasing to be.
   The accurate determination of the first principle in respect of
   form, whether it is one or many and what it is or what they are, is
   the province of the primary type of science; so these questions may
   stand over till then. But of the natural, i.e. perishable, forms we
   shall speak in the expositions which follow.
   The above, then, may be taken as sufficient to establish that
   there are principles and what they are and how many there are. Now let
   us make a fresh start and proceed.
   Book II
   1
   Of things that exist, some exist by nature, some from other causes.
   'By nature' the animals and their parts exist, and the plants and
   the simple bodies (earth, fire, air, water)-for we say that these
   and the like exist 'by nature'.
   All the things mentioned present a feature in which they differ from
   things which are not constituted by nature. Each of them has within
   itself a principle of motion and of stationariness (in respect of
   place, or of growth and decrease, or by way of alteration). On the
   other hand, a bed and a coat and anything else of that sort, qua
   receiving these designations i.e. in so far as they are products of
   art-have no innate impulse to change. But in so far as they happen
   to be composed of stone or of earth or of a mixture of the two, they
   do have such an impulse, and just to that extent which seems to
   indicate that nature is a source or cause of being moved and of
   being at rest in that to which it belongs primarily, in virtue of
   itself and not in virtue of a concomitant attribute.
   I say 'not in virtue of a concomitant attribute', because (for
   instance) a man who is a doctor might cure himself. Nevertheless it is
   not in so far as he is a patient that he possesses the art of
   medicine: it merely has happened that the same man is doctor and
   patient-and that is why these attributes are not always found
   together. So it is with all other artificial products. None of them
   has in itself the source of its own production. But while in some
   cases (for instance houses and the other products of manual labour)
   that principle is in something else external to the thing, in others
   those which may cause a change in themselves in virtue of a
   concomitant attribute-it lies in the things themselves (but not in
   virtue of what they are).
   'Nature' then is what has been stated. Things 'have a nature'which
   have a principle of this kind. Each of them is a substance; for it
   is a subject, and nature always implies a subject in which it inheres.
   The term 'according to nature' is applied to all these things and
   also to the attributes which belong to them in virtue of what they
   are, for instance the property of fire to be carried upwards-which
   is not a 'nature' nor 'has a nature' but is 'by nature' or
   'according to nature'.
   What nature is, then, and the meaning of the terms 'by nature' and
   'according to nature', has been stated. That nature exists, it would
   be absurd to try to prove; for it is obvious that there are many
   things of this kind, and to prove what is obvious by what is not is
   the mark of a man who is unable to distinguish what is self-evident
   from what is not. (This state of mind is clearly possible. A man blind
   from birth might reason about colours. Presumably therefore such
   persons must be talking about words without any thought to
   correspond.)
   Some identify the nature or substance of a natural object with
   that immediate constituent of it which taken by itself is without
   arrangement, e.g. the wood is the 'nature' of the bed, and the
   bronze the 'nature' of the statue.
   As an indication of this Antiphon points out that if you planted a
   bed and the rotting wood acquired the power of sending up a shoot,
   it would not be a bed that would come up, but wood-which shows that
   the arrangement in accordance with the rules of the art is merely an
   incidental attribute, whereas the real nature is the other, which,
   further, persists continuously through the process of making.
   But if the material of each of these objects has itself the same
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   relation to something else, say bronze (or gold) to water, bones (or
   wood) to earth and so on, that (they say) would be their nature and
   essence. Consequently some assert earth, others fire or air or water
   or some or all of these, to be the nature of the things that are.
   For whatever any one of them supposed to have this character-whether
   one thing or more than one thing-this or these he declared to be the
   whole of substance, all else being its affections, states, or
   dispositions. Every such thing they held to be eternal (for it could
   not pass into anything else), but other things to come into being
   and cease to be times without number.
   This then is one account of 'nature', namely that it is the
   immediate material substratum of things which have in themselves a
   principle of motion or change.
   Another account is that 'nature' is the shape or form which is
   specified in the definition of the thing.
   For the word 'nature' is applied to what is according to nature
   and the natural in the same way as 'art' is applied to what is
   artistic or a work of art. We should not say in the latter case that
   there is anything artistic about a thing, if it is a bed only
   potentially, not yet having the form of a bed; nor should we call it a
   work of art. The same is true of natural compounds. What is
   potentially flesh or bone has not yet its own 'nature', and does not
   exist until it receives the form specified in the definition, which we
   name in defining what flesh or bone is. Thus in the second sense of
   'nature' it would be the shape or form (not separable except in
   statement) of things which have in themselves a source of motion. (The
   combination of the two, e.g. man, is not 'nature' but 'by nature' or
   'natural'.)
   The form indeed is 'nature' rather than the matter; for a thing is
   more properly said to be what it is when it has attained to fulfilment