Aristotle · a new plain-English translation from the original language
1| Physics, Book 1 Since knowing and understanding, in all branches of inquiry that have principles, causes, or elements, comes from grasping these (for we think we know each thing only when we have grasped its primary causes, its primary principles, and traced it down to its elements), clearly, in the science concerned with nature as well, we must try first to determine the questions concerning principles. The natural path is from what is more knowable and clearer to us toward what is clearer and more knowable by nature; for the things knowable to us and the things knowable without qualification are not the same. That is why we must proceed in this way: from what is less clear by nature but clearer to us, toward what is clearer and more knowable by nature. Now the things that are plain and clear to us at first are rather confused masses; it is only later, by analyzing these, that their elements and principles become known. That is why we must proceed from the universal to the particular; for the whole is more knowable to perception, and the universal is a kind of whole, since the universal embraces many things as parts. Names, too, stand to their definition in much the same way: a name signifies some whole, undifferentiated—'circle,' say—while its definition divides that whole into its particulars. And children, too, at first call all men 'father' and all women 'mother,' and only later distinguish each of them.
2| The principle must be either one or many. And if one, it must be either unmoved, as Parmenides and Melissus say, or in motion, as the natural philosophers hold—some declaring air to be the first principle, others water. If there are many, they are either limited or unlimited in number; and if limited but more than one, either two or three or four or some other number; and if unlimited, either in Democritus' way—one in genus but differing in shape—or differing in species, or even opposite in kind. In the same way, those who inquire how many the things that are amount to are asking the same question; for they inquire whether the primary constituents from which existing things are made are one or many, and if many, whether limited or unlimited—so that in effect they are asking whether the principle and the element are one or many.
3| Now, to inquire whether what is is one and unmoved is not to inquire about nature. For just as the geometer has no further argument against someone who does away with his principles—that belongs to a different science, or to one common to all sciences—so it is with the one who studies principles as such. For there is no longer a principle at all, if there is only one thing, and one in this way; for a principle is a principle of something, or of several things. So examining whether being is one in this way is much like arguing against any other position stated merely for argument's sake—Heraclitus' thesis, say, or the claim that being is one man—or like refuting an eristic argument, which is exactly what both Melissus' argument and Parmenides' amount to. For both take false premises and are invalid as syllogisms—Melissus' argument more so, being crude and posing no real difficulty: grant one absurdity and the rest follow, and that is no hard thing to do. Let it be assumed by us that the things that exist by nature are, either all or some of them, in motion; this is clear from induction. At the same time, it is not fitting to refute every argument, but only those that draw their false conclusion from the principles of the science in question, and not those that do not; for instance, it belongs to the geometer to refute the squaring of the circle by means of segments, but not to refute Antiphon's version. All the same, since although Parmenides and Melissus are not talking about nature, they do happen to raise difficulties that are natural ones, it is perhaps well to discuss them briefly; for the inquiry has a philosophical interest.
4| The most fitting starting point of all, since being is said in many ways, is to ask in what sense those who say that all things are one mean this: whether they mean that all things are substance, or quantities, or qualities; and again, whether they mean that all things are one substance—one man, say, or one horse, or one soul—or one quality, such as white or hot or some other thing of that kind. For all these positions differ greatly from one another, and are impossible to maintain. For if there is to be substance and quality and quantity all together, whether these are separate from one another or not, then the things that are are many. But if all things are quality or quantity, whether substance exists as well or not, that is absurd—if we should call the impossible absurd. For none of the other categories is separable apart from substance; all of them are said of substance as their subject. Now Melissus says that what is is unlimited. Being is therefore some quantity; for the unlimited belongs among quantities, whereas it is not possible for a substance, a quality, or an affection to be unlimited except accidentally—that is, if these should also happen to be quantities at the same time; for the account of the unlimited makes use of quantity, but not of substance or of quality. If, then, being is both substance and quantity, it is two things and not one; but if it is substance only, it is not unlimited, and will have no magnitude at all—for that would make it a quantity of some sort.
5| Further, since the one itself, like being, is said in many ways, we must examine in what sense they mean that the universe is one. A thing is called one either because it is continuous, or because it is indivisible, or because the things in question have one and the same account of their essence—as, for instance, 'liquor' and 'wine.' If, then, it is one in the sense of continuous, the one is many; for what is continuous is divisible without limit. (There is a puzzle here about the part and the whole—though perhaps it does not bear on the present argument but is worth raising in its own right—namely, whether the part and the whole are one or many, and in what way one or many, and if many, in what way many; and a puzzle too about parts that are not continuous; and whether each part is one with the whole as something indivisible, on the ground that each is one with itself.) But then again, if the one is one in the sense of indivisible, nothing will be a quantity or a quality, and being will be neither unlimited, as Melissus says, nor limited, as Parmenides says; for it is the limit that is indivisible, not the limited thing. But then again, if all existing things are one in account, as 'cloak' and 'coat' are, it turns out that they are saying Heraclitus' thesis. For then to be good and to be bad will be the same, and to be good and not to be good will be the same—so that the same thing will be good and not good, and man and horse; and the argument will no longer be about the things that are being one, but about their being nothing—and being of such-and-such a quality will be the same as being of such-and-such a quantity.
6| The later thinkers among the ancients, too, were troubled that the same thing should turn out for them to be at once one and many. That is why some, like Lycophron, did away with the word 'is,' while others reshaped their phrasing, saying not 'the man is white' but 'the man has been whitened,' and not 'is walking' but 'walks'—so that by attaching the word 'is' they might never make the one turn out to be many, on the assumption that the one, or being, is said in only one way. But things that are, are many, either in account (for being white is different from being musical, though the same subject is both—so the one is many) or by division, as the whole and its parts are many. At this point they were genuinely at a loss, and had to concede that the one is many—as though it were not possible for the same thing to be both one and many, so long as they are not opposites; for a thing is one both potentially and in realization.
7| To anyone who examines it in this way, it appears impossible for the things that are to be one, and it is not hard to refute the arguments by which they try to show it. For both reason eristically — both Melissus and Parmenides. That Melissus commits a fallacy is clear: he thinks he has established that if everything that has come to be has a starting point, then what has not come to be has none. Then this too is strange: that there should be a starting point for the thing in every case but not for time, and one not only for generation in the unqualified sense but for alteration as well — as though change did not happen all at once. Next, why should it be unmoved, if it is one? For just as a part of it that is one — this water here — moves within itself, why should not the whole do so too? Next, why should there not be alteration? But moreover it cannot be one in form either, except in the sense of that out of which it comes (and some of the natural philosophers do call it one in this sense, but not in that other sense); for man differs from horse in form, and contraries differ from one another. And the same kind of arguments apply against Parmenides too,
8| as well as any that are peculiar to him. And the resolution lies partly in the fact that his premise is false, partly in the fact that his conclusion does not follow: false, in that he takes 'being' to be said without qualification, when it is said in many ways; and invalid, because, even if only white things were taken, with 'white' signifying one thing, the white things would nonetheless be many and not one. For the white will not be one either by continuity or by definition. For the being of white will be different from the being of what has received it. And there will be nothing separate over and above the white; for it is not different in the sense of being separable, but in the sense that the white differs in being from that in which it is present. But this Parmenides did not yet see. We must therefore grasp that 'being' does not signify one thing only, of whatever it is predicated, but also signifies a being in the strict sense and a one in the strict sense. For an accident is said of some underlying subject, so that that of which being is an accident will not itself be — for it is other than being; there will therefore be something that is not-being. Being in the strict sense, then, will not exist as belonging to something else. For it will not be possible for it itself to be some being, unless 'being' signifies many things in such a way that each thing is something. But it is assumed that 'being' signifies one thing. If, then, being in the strict sense is an accident of nothing, but the other things are accidents of it, why should being in the strict sense signify being any more than not-being?
9| For if being in the strict sense is also to be white, while being-white is not being in the strict sense (for being cannot be an accident of it either — since nothing that is fails to be being in the strict sense), then the white will not be — not in the sense of being some particular not-being, but of being not-being altogether. Being in the strict sense, then, is not-being; for it is true to say that something is white, and this signified not-being. So white too signifies being in the strict sense; therefore 'being' signifies more than one thing. Being, then, will not have magnitude either, if being is being in the strict sense; for the being of each of its two parts will be different.
10| And that being in the strict sense divides into some other being in the strict sense is clear from its definition too: for example, if man is a being in the strict sense, then animal too must be a being in the strict sense, and two-footed as well. For if it is not a being in the strict sense, it will be accidental — either to man or to some other underlying subject. But that is impossible. For a thing is called accidental either as that which can both belong and not belong, or as that whose definition includes the definition of that to which it belongs (for instance, sitting is an accident in the sense of being separable, whereas in snub the definition of nose is present, in respect of which we say snubness is an accident). Further, whatever is present in the defining account of a thing, or whatever it is composed of, the definition of the whole is not present in the definition of these — for instance, the definition of man is not present in two-footed, nor the definition of white man in white. If, then, this is how things stand, and two-footed is an accident of man, it must be separable, so that it would be possible for man not to be two-footed; or else the definition of man will be present in the definition of two-footed. But that is impossible: for the one is present in the definition of the other. And if two-footed and animal are accidents of something else, and neither of them is a being in the strict sense, then man too would be one of the things that are accidents of something else.
11| But let being in the strict sense be an accident of nothing, and let both be said of that of which it is the subject, and let what is composed of these be said of it too — is the whole, then, made up of indivisibles? Some, indeed, gave way to both these arguments: to the first, that all things are one if 'being' signifies one thing, by conceding that what is not exists; and to the second, the argument from dichotomy, by making magnitudes indivisible. But it is clear also that it is not true that, if 'being' signifies one thing and the contradictory cannot hold at once, there will be nothing that is not-being; for nothing prevents 'what is not' from not existing without qualification, while still being a particular not-being. But indeed to assert that, if there is to be nothing else besides being itself, all things will be one, is absurd. For who understands 'being itself' as anything other than being some being in the strict sense? But if this is so, nothing nonetheless prevents the things that are from being many, as has been said. That it is impossible, then, for being to be one in this way, is clear.
12| As for what the natural philosophers say, there are two ways. Some make the underlying body one — either one of the three elements, or something else that is denser than fire but finer than air — (and these — density and rarity — are contraries, and, in general, excess and deficiency, as Plato speaks of the great and the small, except that he makes these the matter and the one the form, while they make the one the underlying matter, and the contraries differentiae and forms). Others hold that the contraries, being present within the one, are separated out of it, as Anaximander says, and so do all who say that there are both one and many, as Empedocles and Anaxagoras do; for these too separate out everything else from the mixture, but they differ from one another in that the one makes a cycle of this, while the other does it only once, and the one holds there are infinite things — both the homoiomeries and the contraries — while the other holds there are only the so-called elements. Anaxagoras seems to have come to think there are infinite things of this kind because he supposed the common opinion of the natural philosophers to be true — that nothing comes to be from what is not (for this is why they say, 'all things were together,' and coming to be of a given kind has been taken to be alteration, while others take it to be combination and separation);
13| further, from the fact that contraries come to be out of one another — they were present within all along. For if everything that comes to be must come to be either from things that are or from things that are not, and coming to be from things that are not is impossible among these (for on this opinion all who study nature agree), they thought that what remained followed of necessity: that things come to be from things that are and are already present within, but are imperceptible to us because of the smallness of their masses. This is why they say that everything is mixed in everything, because they saw everything coming to be out of everything; but things appear different from one another, and are called by different names, based on whichever ingredient, in the mixture of the infinitely many things, most predominates in quantity; for nothing is purely and entirely white, or black, or sweet, or flesh, or bone, but whatever each thing has the most of — this is thought to be the nature of the thing.
14| If, then, the infinite, qua infinite, is unknowable, then what is infinite in multitude or in magnitude is unknowable as to how much it is, and what is infinite in form is unknowable as to what sort it is. Now if the principles are infinite both in multitude and in form, it is impossible to know the things composed of them; for we suppose we know a composite thing in just this way, when we know from what elements, and how many, it is composed. Further, if it is necessary that, whenever a part can be of any size whatever, large or small, the whole to which it belongs can be so too (I mean one of those parts which, being present in the whole, the whole is divided into), then if it is impossible for an animal or a plant to be of just any size, large or small, it is clear that none of its parts can be either; for the whole will be affected in the same way. Flesh and bone and parts of that sort are parts of an animal, and fruits are parts of plants. It is clear, then, that it is impossible for flesh or bone or anything else to be of just any size whatever, either larger or smaller. Further, if all such things are present in one another, and do not come to be but are separated out while already present, and each is named after whichever ingredient predominates, and anything comes to be out of anything whatever (for example water separated out of flesh, and flesh out of water), while every finite body is eliminated by the subtraction of a finite body, it is clear that it is not possible for each thing to be present in each.
15| For when flesh has been taken away from water, and again more flesh comes to be from what remains by a further separating-out, then even if what is separated out is always smaller, it will nonetheless not go below some minimum magnitude. So that if the separating-out comes to a stop, not everything will be present in everything — for flesh will no longer be present in what remains of the water; but if it does not stop, and there is always a further subtraction to be made, then within a finite magnitude there will be equal finite magnitudes infinite in number; and this is impossible. Besides this, if every body must become smaller once something has been taken from it, and the quantity of flesh is bounded both in largeness and in smallness, then it is clear that no body at all can be separated out from the smallest flesh; for it would have to be smaller than the smallest. Further, among the infinite bodies there would already be present an infinite quantity of flesh, and of blood, and of brain — not separated from one another, yet none the less existing, and each one infinite; and this is absurd. The claim that they will never be separated is made without full understanding, yet it is made correctly; for affections are inseparable. If, then, colors and states have been mixed together, then were they to be separated out, there would be something white, and something healthy, that is nothing else besides that quality, and is not predicated of any underlying subject.
16| So the intellect is absurd in seeking impossibilities, if it wants to separate things out completely, when this is impossible to do both as to quantity and as to quality — as to quantity, because there is no smallest magnitude; as to quality, because affections are inseparable. Nor does he get the coming-to-be of things alike in form right either. For in one sense clay is divided into portions of clay, and in another sense it is not; and it is not in the same way that bricks come from a house and a house from bricks as it is that water and air both are and come to be from each other. It is better to posit fewer principles, and finite ones, as Empedocles does. All thinkers, then, make contraries their principles: both those who say that the universe is one and unmoved (for Parmenides too makes hot and cold his principles, though he calls them fire and earth), and those who posit the rare and the dense, and Democritus, who posits the full and the void, of which he says the one is what is and the other is what is not — further, by position, shape, and arrangement. And these are genera of contraries: of position, up and down, front and back; of shape, angular and unangular, straight and curved. It is clear, then, that everyone in some way makes contraries the principles. And this is reasonable; for the principles must be neither from one another nor from other things, while everything must come from them; and this holds of the primary contraries, because, being primary, they are not from other things, and because, being contraries, they are not from one another.
17| But we must also examine how this turns out in terms of argument. First we must grasp that, of all the things there are, none is by nature such as to act on, or be acted on by, just anything whatever, nor does anything whatever come to be from anything whatever, unless one takes the case accidentally. For how could white come to be from musical, except accidentally, if musical happened to belong to what is not white, or to what is black? No — white comes to be from not-white, and not from just any not-white thing, but from black or from the intermediates; and musical comes to be from not-musical, but again not from just anything, but from unmusical, or from whatever lies between them, if anything does. Nor, again, does a thing perish, in the first instance, into just anything: white does not perish into musical, except perhaps accidentally, but into not-white, and not into just anything, but into black or the intermediate; and likewise musical perishes into not-musical, and this too not into just anything, but into unmusical, or into whatever lies between them, if anything does. And this holds in the same way for the other cases too, since even things that are not simple but composite have the same account —
18| but because the opposed states have not been given names, this fact goes unnoticed. For everything attuned must necessarily come to be from something unattuned, and the unattuned from the attuned, and the attuned perishes into unattunement — and not into just any unattunement, but into the opposite one. And it makes no difference whether we speak of attunement, or of arrangement, or of composition; for clearly the account is the same. And indeed a house, and a statue, and anything else whatever, come to be in the same way: the house comes to be from materials that were not put together but lying apart in such-and-such a way, and the statue, and anything else shaped, comes to be from shapelessness; and each of these is, in one respect, an arrangement, and in another, a kind of composition. If, then, this is true, everything that comes to be would come to be, and everything that perishes would perish, either from contraries or into contraries, or from and into the intermediates between these. And the intermediates are composed of the contraries — for example, intermediate colors are composed of white and black — so that everything that comes to be by nature would be either a contrary or composed of contraries.
19| Up to this point, then, pretty much all the rest of the thinkers have followed the same line, as we said before; for all of them, in positing the elements and what they call the principles, even though they do so without giving any rational account, nonetheless speak of contraries, as though compelled by the truth itself. They differ from one another in that some take principles that are prior, others ones that are posterior; and some take what is more knowable in respect of the account, others what is more knowable in respect of perception (for some posit hot and cold, others wet and dry, still others odd and even, or strife and love, as the causes of coming-to-be; and these differ from one another in the way just stated), so that they say, in a way, both the same things and things different from one another — different, as most people think, but the same, or at least analogous; for they take their principles from the same column of opposites: some of the contraries include others, while some are included by others. In this respect, then, they speak both alike and differently, and both worse and better; and some take what is more knowable in respect of the account, as has been said before, others what is more knowable in respect of perception (for the universal is knowable in respect of the account, the particular in respect of perception; for the account concerns the universal, and perception the particular) — for example, large and small are known in respect of the account, but rare and dense in respect of perception. That the principles, then, must be contraries, is clear.
20| The next thing would be to say whether they are two, three, or more. They cannot be one, because the contraries are not one; nor can they be infinite, because then being would not be knowable, since there is one contrariety in any single genus, and substance is a single genus; and because it is possible to give an account from a finite number of principles, and it is better to do so from a finite number, as Empedocles does, than from an infinite number, as Anaxagoras does — for Empedocles thinks he accounts for everything that Anaxagoras accounts for from the infinite, and does so from a finite number. Further, some contraries are prior to others, and some come to be out of one another, such as sweet and bitter, white and black; but the principles must always remain. That they are, then, neither one nor infinite, is clear from this.
21| Since they are finite in number, there is some reason for not making them only two. For one might raise the difficulty how density is by nature able to do anything to rarity, or rarity to density; and similarly with any other contrariety whatever. For it is not love that draws strife together and makes something out of it, nor strife out of love, but both act on some third thing other than themselves. And some take even more principles than this from which they construct the nature of the things that are. Besides this, one might further raise this difficulty too, unless one posits some other nature underlying the contraries: for we see that the contraries are the substance of nothing among the things that are, yet a principle ought not to be predicated of any underlying subject; for otherwise there will be a principle of the principle, since the underlying subject is itself a principle, and seems to be prior to what is predicated of it. Further, we say that no substance is contrary to a substance; how then could substance come to be from things that are not substances? Or how could a non-substance be prior to a substance? Hence if one judges both the earlier argument and this one to be true, it is necessary, if one means to preserve them both, to posit some third thing, as those do who say that the universe is some single nature, such as water or fire or what is intermediate between these.
22| The intermediate seems the better choice; for fire, earth, air, and water are already bound up with contrarieties. Hence it is not unreasonable that some make the underlying subject something other than these, while others among the rest choose air; for air has the least perceptible differentiae of the others, and water comes next. But all of them, at any rate, give shape to this one thing by means of the contraries, by density and rarity and by the more and the less. And these are, in general, clearly excess and deficiency, as has been said before. And this opinion too, that the one, together with excess and deficiency, are principles of the things that are, seems to be an old one — except not in the same way: the ancients say the two act and the one is acted on, while some of the later thinkers say the contrary rather, that the one acts and the two are acted on.
23| So then, to those who examine the matter on the basis of these and similar considerations, saying that the elements are three would seem to have some reason, as we said, but saying they are more than three no longer seems so; for one thing is sufficient for being acted on, but if there are four, there will be two contrarieties, and each of the two will need, separately, some further intermediate nature belonging to it; and if, being two, they are able to generate things out of one another, then one of the two contrarieties would be superfluous. At the same time it is also impossible for the primary contrarieties to be more than one. For substance is a single genus of being, so that the principles will differ from one another only in being prior and posterior, not in genus; for in any one genus there is always one contrariety, and all contrarieties seem to be reducible to one. That the element, then, is neither one nor more than two or three, is clear; but which of these it is, as we said, presents much difficulty.
24| Let us, then, proceed as follows, first going over the subject of coming-to-be in general; for it is natural, having first stated what is common, to go on in this way to examine what is peculiar to each case. We say that one thing comes to be from another, and a different thing from a different thing, whether we are speaking of simple things or of composite things. I mean this as follows. It is possible for a musical man to come to be, and it is possible for the not-musical to become musical, or for the not-musical man to become a musical man. Now I call the man and the not-musical simple, as what comes to be, and the musical simple too, as what it comes to be; but I call both what comes to be and that which comes to be it composite, when we say that the not-musical man comes to be a musical man. Of these, in one case we say not only that this comes to be, but also that it comes to be out of this — for instance, that the musical comes to be out of the not-musical — but in the other case this is not said in every instance; for the musical did not come to be out of a man, but the man came to be musical. Of the things that come to be in the way we call simple, one persists in coming to be and the other does not persist; for the man persists, remaining a man while becoming musical, but the not-musical, that is, the unmusical, does not persist, either simply or in combination.
25| Now that these distinctions have been made, this can be grasped from all cases of coming-to-be
26| if one looks at it as we are describing: that what comes to be must always have something underlying it, and that this, even if it is one in number, is nonetheless not one in form — for by form I mean the same as by definition, and being a man and being unmusical are not the same thing. And the one persists, the other does not persist: what is not opposite persists (for the man persists), while the not-musical, that is, the unmusical, does not persist, nor does what is composed of both, such as the unmusical man. Saying that something comes to be out of something, rather than that this comes to be something, is said more properly of things that do not persist — for instance, that the musical comes to be out of the unmusical, but not out of the man; not but that it is sometimes said in the same way of things that persist too, for we say that a statue comes to be out of bronze, not that the bronze becomes a statue. In the case, however, of what comes from the opposite and does not persist, it is said both ways, both that this comes from this and that this becomes this; for indeed the musical comes to be both out of the unmusical and as the unmusical man becoming musical. Hence it is the same too in the case of the composite: for indeed we say both that the musical comes to be out of an unmusical man, and that the unmusical man becomes musical. Since coming-to-be is spoken of in many ways, and of some things we do not say without qualification that they come to be, but that they come to be a certain something, while it is only substances that are said to come to be without qualification, in the other categories it is clear that what comes to be must have something underlying it (for indeed a quantity, a quality, a relation, and a place come to be only when something underlies them, because it is substance alone that is not said of any other underlying subject, while everything else is said of a substance).
27| That substances too, and whatever else exists without qualification, come to be out of some underlying subject, would become clear to one who examines the matter. For there is always something underlying, out of which what comes to be comes to be, as plants and animals come to be out of seed. And things that come to be without qualification come to be, some by change of shape, such as a statue; some by addition, such as things that grow; some by subtraction, such as the Hermes carved out of the stone; some by combination, such as a house; and some by alteration, such as things that are transformed in respect of their matter. And it is clear that all things that come to be in these ways come to be out of things underlying them. So it is clear from what has been said that everything that comes to be is always composite, and that there is, on the one hand, something that comes to be, and, on the other, something which becomes this, and this latter is twofold: for it is either the underlying subject or the opposite. By opposite I mean the unmusical, and by underlying subject I mean the man; and shapelessness, formlessness, and disorder are the opposite, while the bronze, the stone, or the gold is the underlying subject. It is clear, then, that, if there are causes and principles of the
28| ...that exist by nature — from what primary things they are and have come to be, not accidentally, but each thing insofar as it is spoken of in respect of its substance — that everything comes to be from both the underlying subject and the form. For the musical man is composed, in a way, of man and musical: you can resolve him into the accounts of these. It is clear, then, that things that come to be would come to be from these. Now the underlying subject is one in number but two in form (for the man, and the gold, and matter in general, are countable — each is more properly a this-something, and what comes to be does not come from it accidentally; whereas privation and contrariety are accidental); and the form is one, for instance order, or musical skill, or whatever else of the things predicated in this way. Hence in one sense the principles must be said to be two, and in another sense three; and in one sense they are the contraries, as if one were to say the musical and the unmusical, or the hot and the cold, or the attuned and the unattuned, but in another sense they are not, since it is impossible for the contraries to be acted on by one another. This too is resolved by the fact that the underlying subject is something different: for that is not a contrary. So the principles are, in a way, not more than the contraries — two, so to speak, in number — yet they are not simply two either, because their being is not the same for the two of them, but three: for what it is to be man is different from what it is to be unmusical, and what it is to be shapeless is different from what it is to be bronze.
29| How many, then, the principles of natural things that come to be are, and in what way they are that many, has been stated; and it is clear that there must be something underlying the contraries, and that the contraries must be two. In another sense this is not necessary: for it will be enough for one of the two contraries to produce the change by its absence and presence. The underlying nature is knowable by analogy. For as bronze stands to a statue, or wood to a bed, or the shapeless to any other of the things that have form, before it takes on the form, so this underlying nature stands to substance, to the this-something, and to being. This, then, is one principle — not one, nor a being, in the way a this-something is, but one in the sense that its account is one — and there is, further, the contrary to this, namely privation. In what way these are two and in what way more has been said above. First it was said that the principles were only the contraries; later, that something else too must underlie them, and that they are three. From what has now been said it is clear what the difference between the contraries is, how the principles stand to one another, and what the underlying subject is. But whether it is the form or the underlying subject that is substance is not yet clear. What is clear is that the principles are three, in what way they are three, and what their manner of being is. Let this, then, serve as our study of how many the principles are and what they are.
30| Let us next say that it is only in this way that the difficulty of the ancients, too, is resolved. For the first of those who pursued philosophy in search of the truth and the nature of things that exist were turned aside, as it were onto another road, pushed off course by inexperience, and they say that nothing that exists either comes to be or perishes, on the ground that what comes to be must come to be either from what is or from what is not, and that it is impossible to come to be from either of these: for what is cannot come to be, since it already is, and from what is not nothing could come to be, since something must underlie it. And so, magnifying what follows from this, they go on to say that not even the many exist, but only being itself.
31| Those thinkers, then, adopted this view for the reasons stated. But we say that to come to be from what is or from what is not, or for what is not or what is to act or be acted on or to become some particular thing, is in one sense no different from saying that a doctor does something, or is acted on, or comes to be something, or comes to be from a doctor. Since this last is said in two ways, it is clear that the same holds for coming to be from what is, and for what is either acting or being acted on. So the doctor builds a house not insofar as he is a doctor but insofar as he is a builder, and he becomes pale not insofar as he is a doctor but insofar as he is dark; but he practices medicine, and ceases to be skilled in medicine, insofar as he is a doctor. Since we say, in the strict and proper sense, that the doctor does something, or is acted on, or comes to be something, from a doctor, only when it is insofar as he is a doctor that he undergoes, does, or becomes these things, it is clear that coming to be from what is not means this too: coming to be insofar as it is not. This is the distinction those thinkers failed to draw, and so they abandoned the inquiry; and through this ignorance they went on to a further ignorance so great that they supposed nothing else comes to be or exists at all, and did away with all coming-to-be. We ourselves say that nothing comes to be, without qualification, from what is not, but that in a sense things do come to be from what is not, namely accidentally. For a thing comes to be from privation, which in its own right is a not-being not present in the thing —
32| and this is found astonishing, and it seems impossible for something to come to be in this way, from what is not. Likewise, too, what is does not come to be from what is, nor does what is come to be at all, except accidentally; but in this same sense it too comes to be — just as, for instance, if an animal were to come to be from an animal, and some particular animal from some particular animal, as if a dog were to come to be from a dog, or a horse from a horse. For the dog would come to be not only from some particular animal, but also from an animal — yet not insofar as it is an animal, since this already belongs to it. But if something is going to come to be an animal, not accidentally, it will not be from an animal; and if it is going to come to be something that is, it will not be from what is — nor yet from what is not, for we have already said what coming to be from what is not means: coming to be insofar as it is not. Further, we are not doing away with the principle that everything either is or is not. This, then, is one way of resolving the difficulty; another is that it is possible to say the same things in terms of potentiality and actuality, but this has been determined elsewhere with greater precision. So, as we were saying, the difficulties are resolved that force people, when pressed, to do away with some of the things stated; and it was for this very reason that the earlier thinkers were turned aside so far from the road leading to coming-to-be and perishing and change in general — for if this nature had been seen, it would have resolved the whole of their ignorance.
34| There are others, too, who have laid hold of this nature, but not adequately. In the first place, they agree that something comes to be, without qualification, from what is not, granting that far Parmenides was right. Next, it seems to them that, if this nature is one in number, it must also be one in potentiality only. But this makes a very great difference. For we say that matter and privation are different things, and that of these, matter is not-being accidentally, while privation is not-being in its own right; and that matter is close to substance and in a way is substance, while privation is not, in any way. But they hold that not-being is the great and the small alike — either the two together, or each separately. So this triad of theirs is entirely different from ours. They got as far as this: that some nature must underlie the contraries; but they make this a single thing. For even if someone makes it a dyad, calling it the great and the small, he is doing no less the same thing — he has simply overlooked the other one. For the nature that persists is a joint cause, along with the form, of the things that come to be, like a mother; but the other portion of the contrariety might often appear, to one who fixes his thought on its harmful aspect, not to exist at all. For given that there is something divine and good and desirable, we say that the one thing is contrary to it, while the other is what by its nature desires it and reaches for it, in accordance with its own nature. But on their view it turns out that the contrary desires its own destruction. Yet the form cannot desire itself, since it is not lacking anything, nor can the contrary desire it, for contraries are destructive of one another. No, it is matter that does the desiring, as the female desires the male and the ugly the beautiful — except that it is not ugly in its own right, but accidentally, nor female in its own right, but accidentally.