On Generation and Corruption · Book I

Aristotle · a new plain-English translation from the original language

1| ON GENERATION AND CORRUPTION, Book 1. Concerning the generation and corruption of things that come to be and perish by nature, we must distinguish alike, for every case, the causes and the accounts of them, and further, concerning growth and alteration, what each of these is, and whether we should suppose alteration and generation to be the same nature, or distinct, as they are indeed distinguished by their very names. Now among the ancients, some say that what is called unqualified generation is alteration, while others say alteration and generation are different. For those who say the universe is some one thing, and generate everything from one, are necessarily forced to say that generation is alteration, and that what comes to be in the strict sense is being altered; but those who posit more than one matter, such as Empedocles and Anaxagoras and Leucippus, hold it to be something different. And yet Anaxagoras at least misunderstood his own language; at any rate he says that coming-to-be and perishing are the same thing as being altered. And he speaks of many elements, as the others do too. For Empedocles says the bodily elements are four, but all of them together with the moving causes are six in number, while Anaxagoras and Leucippus and Democritus say they are infinite. For the one posits the homoeomerous things as elements, such as bone and flesh and marrow, and each of the others of which the part has the same name as the whole; but Democritus and Leucippus say that everything else is composed

2| out of indivisible bodies, and that these are infinite both in number and in shapes, and that and that the compounds differ from one another in respect of the constituents out of which they are composed, and by the position and arrangement of these. Anaxagoras and his followers appear to say the opposite of Empedocles and his followers; for the one says fire and water and air and earth are four elements and simple, more so than flesh and bone and such homoeomerous things, while the others say these are simple and are the elements, but that earth and fire and water and air are composite; for these are a seed-mixture of all things. Now for those who construct everything out of one thing, it is necessary to say that generation and corruption are alteration; for the substrate always remains the same and one, and we say that such a thing is being altered; but for those who make the kinds more than one, alteration differs from generation; for generation and corruption occur when things come together and are dissolved. This is why Empedocles too speaks in this way, saying that there is no coming-to-be of anything, but only mixing and interchange of what has been mixed. It is clear, then, that it is appropriate to their hypothesis for them to speak in this way, and that they do speak in this manner; but it is necessary for them too to say that alteration is something distinct from generation, though this is impossible on the basis of what they themselves say.

3| That we are right to say this is easy to see. For just as we observe, while the substance itself remains at rest, a change occurring in it with respect to magnitude — what is called growth and diminution — so too we observe alteration. Yet from what those say who make the principles more than one, alteration turns out to be impossible. For the affections in respect of which we say this happens are the differentiae of the elements — I mean, for example, hot and cold, white and black, dry and wet, soft and hard, and each of the others — just as Empedocles too says: 'the sun, white to see and hot everywhere, but the rain, in all things dark and cold.' And he distinguishes the rest similarly. So that if it is not possible for water to come to be from fire, nor earth from water, then neither will anything black come to be from white, nor anything hard from soft; and the same account holds for the others too. But this was alteration. From which it is also clear that we must always suppose a single matter underlying the contraries, whether the change is with respect to place, or with respect to growth and diminution, or with respect to alteration. Further, it is likewise necessary that this be alteration as well; for if it is alteration, then the substrate is one element, and there is a single matter for all the things that change into one another; and conversely, if the substrate is one, there is alteration.

4| Empedocles, then, seems to say things that conflict both with the appearances and with himself. For at one time he says that none of the elements comes to be from any other, but that all the other things come from these; and at the same time, whenever he draws the whole of nature together into one, apart from Strife, he has each thing coming to be again out of the one. So it is clear that, out of some one thing, by certain differentiae and affections coming apart, water came to be on one side and fire on the other, just as he says the sun is white and hot, and the earth heavy and hard. If, then, these differentiae are taken away (and they can be taken away, since they came to be), it is clear that earth must come to be from water, and water from earth, and likewise each of the others too, not only then but even now, since they change with respect to their affections. And on the terms of his own account, these things are capable of being added and separated off again, especially since Strife and Love are still fighting one another. This is also why they were generated at that time out of one thing; for surely, while fire and earth and water still existed as such, the universe was not yet one. But it is also unclear whether we should posit the one as their principle, or the many — I mean fire and earth and the elements ranked with these.

5| For insofar as it underlies as matter, out of which earth and fire come to be by changing through motion, the one is the element; but insofar as this one comes to be by composition when those elements come together, while those elements come to be by dissolution of the one, those are more elemental, and prior in nature. We must speak, then, in general terms about unqualified generation and corruption — whether it exists or not, and how it exists — and likewise about the other simple motions, such as growth and alteration. Now Plato inquired only into generation and corruption, how these belong to things, and into the generation not of everything but only of the elements; but as to how flesh or bones or any other such thing comes to be, he said nothing at all; nor again about alteration or about growth, in what manner these belong to things. And in general, beyond what lies on the surface, no one has attended closely to any of this, except Democritus. He seems to have given thought to everything, but already differs from the rest precisely in the how. For no one has determined anything about growth, as we say, beyond what even an ordinary person might say — that things grow by the addition of what is like to them (but how this happens, no longer) — nor about mixture, nor, one might almost say, about anything else at all, such as acting and being acted on, in what way the one thing acts and the other undergoes the natural actions. But Democritus and Leucippus, having posited the shapes, construct alteration and generation out of these: generation and corruption by separation and combination, but alteration by arrangement and position.

6| And since they supposed the truth lay in what appears, and the appearances are contrary to one another and infinite, they made the shapes infinite, so that, through the changes of the compound, the same thing seems contrary to one observer and another, and shifts when a small amount is mixed in, and appears altogether different when a single element has shifted; for tragedy and comedy come to be out of the same letters. Now since it seems to almost everyone that generation and alteration are different, and that things come to be and perish by being combined and separated, while they are altered by a change in their affections, we must attend to these questions and examine them. For they involve many reasonable difficulties. For if generation is combination, many impossible consequences follow; yet there are, in turn, other compelling arguments, not easy to resolve, to the effect that it cannot be otherwise. And if generation is not combination, then either there is no generation or alteration at all, or else — difficult though it is to resolve — we must attempt it. The starting point for all these questions is whether existing things come to be and are altered and grow, and undergo the contraries of these, on the supposition that there are certain first, indivisible magnitudes, or whether no magnitude is indivisible; for this makes the greatest difference. And again, if there are such magnitudes, whether, as Democritus and Leucippus hold, these are bodies, or, as in the Timaeus, planes.

7| This point itself, as we have said elsewhere too, is unreasonable — to dissolve bodies down to planes. Hence it is more reasonable that there be indivisible bodies. But these too involve much unreasonableness. Nevertheless it is possible for them to produce alteration and generation, as has been said, by shifting the same material about through turning and through contact, and by the differences of shapes — which is what Democritus does. That is why he says there is no such thing as color; for things get colored by turning. But for those who divide bodies into planes this is no longer possible, since nothing comes to be except solids by combination; they do not even attempt to generate any affection out of these planes. The cause of their being less able to take in the agreed facts together is inexperience. That is why those who have lived more within the study of nature are more able to posit such principles as can hold many things together in a connected account, while those who are unobservant of the facts because of much arguing look at only a few things and pronounce their views more readily. One can see from the following, too, how far apart those who inquire as natural scientists and those who inquire as logicians are: concerning the existence of indivisible magnitudes, some say it must be so because the triangle-itself would otherwise be many, whereas Democritus would appear to have been persuaded by arguments proper to and characteristic of natural science. What we mean will be clear as we go on. For there is a puzzle if one posits that there is some body and magnitude divisible through and through, and that this is possible.

8| For what will there be that escapes the division? For if it is divisible through and through, and this is possible, then this could also actually be the case at once, this body being divided through and through, even if it has not been divided all at once; and if this came about, nothing impossible would result. So too with respect to the middle point, likewise. And in general, if it is by nature divisible through and through, then even if it is actually divided, nothing impossible will have resulted, since not even if it has been divided into ten thousand times ten thousand parts is anything impossible involved — though perhaps no one would actually carry out the division. Since, then, the body is everywhere of this kind, let it be divided. What, then, will be left over? A magnitude? That cannot be, for there would then be something undivided, yet it was divisible through and through. But then, if there will be no body and no magnitude, yet division will still occur, either the body will consist of points, and the things it is composed of will be without magnitude, or there will be nothing at all, so that it would come to be out of nothing and be composed of nothing, and the whole would be nothing but an appearance. Likewise, even if it consists of points, it will not be a quantity. For when the points were in contact and were one magnitude and existed together, they made the whole no greater. For when the whole is divided into two parts or more, it is no less and no greater than it was before, so that even if all the points are put together, they will produce no magnitude.

9| But further, if something comes off the body as it is divided, like a sawn-off chip, and in this way some body departs from the magnitude, the same argument applies: how is that departing piece itself divisible? But if what departs is not a body but some separable form or affection, and the magnitude consists of points or contacts that have undergone this affection, it is absurd that a magnitude should consist of things that have no magnitude. Further, where will the points be, and will they be motionless or in motion? And a contact is always a relation between two things, as though there were something besides the contact and the division and the point. If, then, one posits that any body whatever, of any size whatever, is divisible through and through, all these consequences follow. Further, if I divide a piece of wood, or anything else, and then put it back together, it is again equal and one. So this evidently holds no matter at what point I cut the wood. It has, then, been divided through and through, potentially. What, then, is there besides the division? For even granting there is some affection, still, how does the wood dissolve into these points, and come to be out of them? Or how are these points separated out? So that, since it is impossible for magnitudes to consist of contacts or points, there must be indivisible bodies and magnitudes. And yet even positing these, no fewer impossible consequences follow.

10| These matters have been examined elsewhere. But we must try to resolve them, so let us state the puzzle again from the beginning. That every perceptible body is divisible at any point whatever, and also indivisible, is not at all absurd, for the one holds potentially, the other will hold in actuality. But that it should be divisible through and through at once, in potentiality, would seem to be impossible. For if it is possible, it could also come about — not so that both conditions hold at once in actuality, undivided and divided, but rather divided at every point. Nothing, then, will be left over, and the body will have been dissolved into something incorporeal. And it would come to be again either out of points or out of nothing whatsoever. And how is this possible? But that a body is divided into separable parts, and always into smaller magnitudes, and into parts that stand apart from and separated from one another, is evident. Neither, then, would the crumbling be infinite if one divides part by part, nor is it possible for the body to be divided at every point at once — for that is not possible — but only up to a certain point. There must, therefore, be indivisible magnitudes present within it, invisible ones, especially if there is to be generation and corruption, the one by dissociation, the other by association. This, then, is the argument that seems to compel the existence of indivisible magnitudes.

11| Let us say wherein it goes unnoticed in committing its fallacy, and how it goes unnoticed. For since a point is not next to a point, being divisible through and through belongs to magnitudes in one sense but not in another. It is thought, once this is posited, that there is a point in any place whatever, and at every point, so that the magnitude must be divided into nothing, since there is supposed to be a point everywhere, and so it must consist either of contacts or of points. But the sense in which it holds everywhere is this: that there is one point taken in whatever place we like, and all points are so taken, each in its own place, but they are not more than one at any place, for they do not stand in succession, so that it is not divisible everywhere in that sense — for if it is divisible at the middle point, it will also be divisible at the point next to it, and yet there is no point next to a point, nor contact next to contact. It is in this way that there is division, or rather combination. So there is indeed both dissociation and association, but not into indivisibles and out of indivisibles, for that involves many impossibilities, nor in such a way that division occurs through and through, for that would hold only if there were a point next to a point; rather, division is into small and ever smaller parts, and association is out of smaller parts. But simple and complete generation is not defined by association and dissociation, as some say, whereas the change that occurs within the continuous is rightly called alteration.

12| But this is exactly the point at which everyone goes wrong. For there is simple generation and corruption not by association and dissociation, but when a thing changes as a whole from this into that. But they suppose every such change to be alteration; and in this they are mistaken, for it differs. In the substrate, one aspect belongs to it according to its account, the other according to its matter. When, then, the change occurs in these — in what belongs according to the account — there will be generation or corruption; but when it occurs in the affections, and accidentally, it is alteration. Things that are being dissociated and associated become easily destructible. For if water is divided into smaller portions of water, it turns into air more quickly, but if it is combined together, more slowly. This will become clearer later on. For now let this much be determined: that it is impossible for generation to be association, of the sort some assert it to be.

13| Now that these points have been determined, we must first consider whether there is something that comes to be and perishes without qualification, or whether, properly speaking, nothing does, but there is always something that comes to be, and comes to be something, out of something — I mean, for example, a healthy thing out of a sick one and a sick thing out of a healthy one, or a small thing out of a large one and a large thing out of a small one, and everything else in the same way. For if there is to be generation without qualification, something would come to be without qualification out of what is not, so that it would be true to say that not-being belongs to certain things. For generation of a particular thing is out of what is not that particular thing — for example, out of what is not white, or not fine — but simple generation is out of what simply is not. Now, without qualification signifies either the first thing in respect of each category of being, or else the universal, that which embraces all things. If, then, it means the first, there will be generation of substance out of not-substance. But that to which substance does not belong, nor thisness, clearly none of the other categories belongs to it either,

14| for example, neither of quality nor of quantity nor of place — for then the affections would be separable from substances. But if they were, not-being would be an entirely universal negation of everything, so that what comes to be would necessarily come to be from nothing. Now about these matters there has been discussion and fuller determination elsewhere in our accounts; but briefly, here too, it must be said that in one way a thing comes to be from what is not, without qualification, and in another way always from what is. For what is potentially, but not actually, must pre-exist, spoken of in both senses. But there is a further difficulty here, remarkable even once these points are settled, which we must go back over: how is unqualified coming-to-be possible — whether it proceeds from what is potentially, or in some other way? For one might raise the difficulty whether there is coming-to-be of substance and of a this, but not of a such, a so-much, and a where. The same holds for perishing. For if something comes to be, clearly there will be some substance potentially, but not actually, from which the coming-to-be will proceed and into which what perishes must change. Will, then, anything of the other kinds belong to this actually? I mean, for example, will the thing that is only potentially a this and a being, but without qualification not a this nor a being, be a quantity or a quality or a where?

15| For if nothing is actually but everything is potentially, it follows that what is not in this way is separable, and further, that thing which those who first philosophized were most afraid of all along persists: coming-to-be from nothing pre-existing. But if being a this or a substance will not belong to it, while some one of the other things mentioned will, then, as we said, the affections will be separable from substances. We must, then, treat these matters as far as possible, and also ask what the cause is of coming-to-be always occurring, both unqualified coming-to-be and coming-to-be in part. Since there is one cause, from which we say the principle of motion is, and another, that of matter, it is this latter kind of cause we must speak of; for the former has been discussed earlier, in our accounts of motion — that one thing is unmoved for all time, while another is always in motion. Of these, to distinguish the unmoved principle, the other and prior one, is the work of a different and prior philosophy; but concerning the thing that moves other things because it is itself continuously in motion, we must give an account later, saying what particular thing among things spoken of individually is the cause of this. For now let us state the cause posited as being in the form of matter, on account of which perishing and coming-to-be never fail nature —

16| for perhaps this same inquiry will at once make clear also the point we are now at a loss about, namely how one ought to speak about unqualified perishing and coming-to-be too. There is also sufficient difficulty in what the cause is of coming-to-be being unbroken, if indeed what perishes departs into not-being, and not-being is nothing at all — for not-being is neither a this, nor a quality, nor a quantity, nor a where. If, then, something among the things that are is always departing, why has the universe not long since been used up and gone, given that what each of the things coming to be comes from was finite? For surely it is not because that from which it comes to be is infinite that it does not fail — that is impossible. For nothing is actually infinite, only potentially, by division; so that this would have to be the only account that does not fail, on the ground that what comes to be is always less; but as it is, we do not see this happening. Is it, then, because the perishing of this thing is the coming-to-be of another, and the coming-to-be of this thing is the perishing of another, that change must necessarily be unceasing? As for there being coming-to-be and perishing alike concerning each of the things that are, this must be thought a sufficient cause for all of them.

17| We must consider again why it is that some things are said to come to be and perish without qualification, while others are not said to do so without qualification, given that it is the same change that is the coming-to-be of this thing and the perishing of that, and the perishing of this thing and the coming-to-be of that; for this calls for some account. We say, for example, that this now perishes without qualification, and not merely as this particular thing; and this change is coming-to-be without qualification, while that one is perishing. But this other thing comes to be something, yet does not come to be without qualification — for we say that the person learning comes to be knowing, but does not come to be without qualification. So then, just as we often draw the distinction that some things signify a this and others do not, this is the reason the point in question arises; for it makes a difference into what the changing thing changes. For example, perhaps the road to fire is unqualified coming-to-be, but is the perishing of some particular thing, namely earth, while the coming-to-be of earth is coming-to-be of a particular thing — coming-to-be not without qualification, but perishing without qualification, namely of fire — just as Parmenides says there are two things, being and not-being, calling them fire and earth. Now it makes no difference whether we posit these or other things like them; for we are inquiring into the manner, not the substrate. The road to not-being without qualification, then, is unqualified perishing, and the road to being without qualification is unqualified coming-to-be.

18| Among the things thus distinguished, then, whether fire and earth or certain others, one of them will be being and the other not-being. In one way, then, unqualified coming-to-be and perishing will differ from what is not unqualified by this; in another way, by whatever the matter happens to be. For that matter whose differentiae signify a this more, is more substance, while that whose differentiae signify privation is not-being — for example, the hot is a certain predicate and form, while coldness is privation. Earth and fire also differ by these very differentiae. But most people think they differ rather by the perceptible and the non-perceptible; for they say that when a thing changes into perceptible matter, it comes to be, and when into something not apparent, it perishes — for they distinguish being and not-being by perceiving and not perceiving, just as the knowable is being, and the unknowable is not-being; for perception has the power of knowledge. So then, just as they themselves think they live and are by perceiving, or by being able to, so too they think this of things, in a way pursuing the truth, though what they say is not true. It turns out, then, that coming-to-be and perishing without qualification are different according to opinion and according to truth —

19| for breath and air are, according to perception, less real (which is why people say that things which perish without qualification perish by changing into these, and come to be when they change into what is tangible and into earth), but according to truth these are rather more a this and a form than earth is. As to why unqualified coming-to-be is the perishing of something, while unqualified perishing is the coming-to-be of something, the cause has been stated; for it is because the matter differs, either by being substance

20| or not, or by the one being more so and the other not, or by the matter — that out of which and into which the change occurs — being more perceptible in the one case and less so in the other. As for why some things are said to come to be without qualification, while others are said only to come to be something, not by coming-to-be from one another, in the way we have just now stated — for now this much has been determined: why, though every coming-to-be is the perishing of something else, and every perishing is the coming-to-be of something else, we do not attribute coming-to-be and perishing in the same way to things that change into one another. But the point raised afterward does not concern this difficulty, but rather why it is that the thing learning is not said to come to be without qualification, but to come to be knowing, while the thing growing is said to come to be. These matters are distinguished by the categories: for some things signify a this, others a such, and others a quantity. So whatever does not signify substance is not said to come to be without qualification, but to come to be something. Nonetheless, alike in all cases, coming-to-be is spoken of in accordance with the things in the other column of the table of opposites — for example, in the category of substance, if it becomes fire but not if it becomes earth; and in the category of quality, if it becomes knowing but not when it becomes unknowing.

21| We have then discussed the question why some things come to be without qualification and others do not, and this in general, and also in the case of substances themselves; and why the substrate is, as matter, the continuous cause of there being coming-to-be, namely because it is capable of changing into its contraries, and why, among substances, the coming-to-be of one thing is always the passing-away of another, and the passing-away of one thing is the coming-to-be of another. Moreover, there is no need to raise a puzzle about why things always come to be even while other things are constantly perishing; for just as people say that a thing perishes without qualification when it passes into what is imperceptible and into what is not, so likewise they say that a thing comes to be out of what is not, when it comes from what is imperceptible. So whether or not there is some substrate, it comes to be out of what is not. Hence in the same way a thing both comes to be out of what is not and perishes into what is not. It is reasonable, then, that this process never gives out; for coming-to-be is the passing-away of what is not, and passing-away is the coming-to-be of what is not. But as to this "what is not" without qualification, one might raise the puzzle whether it is the one member of a pair of contraries — for example whether earth and the heavy are what is not, and fire and the light are what is — or whether this is not so, but earth too is what is, while what is not is the matter of earth, and likewise the matter of fire.

22| And is the matter of each different, or would things then not be able to come to be out of one another nor out of contraries? For the contraries belong to these — fire, earth, water, air — 319b. Or is it in one sense the same, in another sense different? For that which underlies, considered as something that at some time is, is the same, but its being is not the same. Let this much, then, be said about these matters.

23| 4 Let us now discuss how coming-to-be and alteration differ; for we say that these are changes distinct from one another. Since, then, there is a substrate, and there is, distinct from it, an affection which by nature is said of the substrate, and there is change of each of these, alteration occurs when the substrate persists, being perceptible, and changes in its own affections — whether these are contraries or intermediates — as for example the body is healthy and again becomes sick while remaining the same, and the bronze is round and at another time angular while remaining the same bronze. But when the whole changes without anything perceptible persisting as the same substrate — as, for instance, all the semen becomes blood, or water becomes air, or all the air becomes water — such a case is already coming-to-be, and for the other thing passing-away, and especially so when the change occurs from what is imperceptible to what is perceptible either by touch or by all the perceptions, as when water comes to be or perishes into air; for air is fairly imperceptible. But in these cases, if some affection belonging to the same contrariety persists the same in both what has come to be and what has perished — for example when water comes from air, if both are transparent or both moist — the affection into which it changes need not belong to this persisting thing. But if it does, it will be alteration — as when the musical man perishes and an unmusical man comes to be, while the man persists as the same. If, then, musicality and unmusicality were not in their own right an affection of this thing, there would be coming-to-be of the one and passing-away of the other; hence these are affections of the man, but there is coming-to-be and

24| passing-away of the musical man and the unmusical man. But as it is, this is an affection of what persists; and that is why such cases are alteration. So then, when the change of the contrariety is in respect of quantity, it is growth and diminution; when in respect of place, locomotion; when in respect of affection and quality, alteration; but when nothing persists of which the one thing is an affection or an accident at all, it is coming-to-be, and for the other thing, passing-away. Matter, in the fullest and most proper sense, is the substrate receptive of coming-to-be and passing-away, but in a certain way it is also the substrate for the other changes, because all substrates are receptive of certain contrarieties. Let coming-to-be and passing-away, then — whether they exist or not, and how they exist — and alteration, be determined in this way.

25| 5 It remains to speak about growth: how it differs from coming-to-be and alteration, and how each of the things that grow grows, and how anything that diminishes diminishes. We must first consider whether their difference from one another lies only in what they are changes about — for example, that the change from this to that, as from substance potentially to substance actually, is coming-to-be, while the change with respect to magnitude is growth and diminution, and the change with respect to affection is alteration — or whether both of these latter are also, like the cases mentioned, a change from what is potentially to what is in actuality, and the manner of the change differs as well; for it is evident that what is altered does not necessarily change in respect of place, nor does what comes to be, but what grows and what diminishes does change in respect of place, though in a manner different from that of what is carried along. For what is carried along changes place as a whole, whereas what grows does so as a thing being hammered out does: for while it as a whole remains, its parts change place, and not as the parts of a sphere do; for the parts of a sphere change within an equal place while the whole remains, but the parts of what grows always move into a greater place, and the parts of what diminishes into a smaller. It is clear, then, that the change differs not only in respect of what it concerns but also in manner, as between what comes to be, what is altered, and what grows.

26| As to what the change of growth and diminution is about (for growing and diminishing seem to concern magnitude), how are we to understand it — whether body and magnitude come to be out of what is potentially magnitude and body but actually incorporeal and without magnitude; and since this can be said in two ways, in which way does growth occur? Is it out of matter that is separated and by itself, or out of matter existing within another body? Or is each of these two ways impossible? For if it is separate, it will either occupy no place at all, or it will be like a point, and it will be a void, and a body that is imperceptible. But of these, the one is not possible, while the other requires it to be in something; for that which comes to be from it will always be somewhere, so that it too will be somewhere, either in its own right or accidentally. But then, if it exists in something, and if it is separated from that thing in such a way that it is not, either in its own right or accidentally, anything belonging to it, many impossibilities will follow. I mean, for example, that if air comes to be out of water, this will not be because the water changes, but because its matter is in the water as though in a vessel. For nothing prevents there being infinitely many matters, such that they also come to be in actuality.

27| Moreover, air does not even appear to come to be out of water in this way, as though it came out of it while the water remained. It is better, then, to hold that matter is inseparable for all these things, being the same and one in number, but not one in account. But indeed neither should points nor lines be taken to be the matter of body, for the same reasons. Rather, that of which these are the limits is matter, and matter can never exist without affection nor without shape. One thing, then, comes to be without qualification out of another, as has also been determined elsewhere, and always by the agency of something that actually is, either of the same form or of the same genus — as fire by fire, or man by man — or by the agency of actuality; for hard does not come to be by the agency of hard. But since there is also matter of corporeal substance, and already matter of a body of this or that kind (for there is no body in general), the same matter belongs to magnitude and to affection, separable in account but not separable in place, unless the affections too are separable. It is clear, then, from the puzzles raised, that

28| Growth is not a change from a magnitude that exists potentially to something having, in actuality, no magnitude at all; for then the void would be separable, and that this is impossible has been stated elsewhere before. Moreover, a change of that kind would not be distinctive of growth but of coming-to-be; for growth is an increase of a magnitude already present, and wasting away is a decrease of it. Hence what grows must already have some magnitude. So growth into the actuality of magnitude must not proceed out of matter that has no magnitude at all; for that would be the coming-to-be of a body rather than growth. We should instead take hold of the inquiry again from the beginning, as it were, and ask what sort of thing growing or wasting away is when we seek its causes. Now it appears that any part whatever of the thing growing has grown, and likewise in wasting away that it has become smaller; further, that a thing grows by something coming to it and wastes away by something leaving it. It is necessary, then, that growth occur either by means of something bodiless or by means of a body. If by something bodiless, the void will be separable; but it is impossible for the matter of magnitude to be separable, as has been said before. But if by a body, there will be two bodies in the same place, the thing that grows and the thing that makes it grow; and this too is impossible. But neither can one say that growth or wasting away comes about in the way that air comes to be from water—

29| for then the bulk has become greater; but this is not growth, but rather the coming-to-be of that into which the thing changed, and the destruction of its contrary; growth belongs to neither of these, but either to nothing, or, if there is something common to both, to the thing that comes to be and the thing destroyed, for instance if it is body. But the water has not grown, nor has the air; rather the one has perished and the other has come to be; but the body, if anything, has grown. But this too is impossible. For we must preserve in our account the features that belong to the thing that grows and wastes away. These are three: one is that any part whatever of the growing magnitude becomes greater, for instance, if it is flesh, greater by flesh; a second, that this happens by something coming to it; and a third, that the thing growing is preserved and persists. For in unqualified coming-to-be or perishing nothing persists, but in being altered, or growing, or wasting away, the very thing that grows or is altered persists as the same; but there, in alteration, it is the affection, and there, in growth, the magnitude, that does not remain the same. If, then, the growth we have described is to occur, it would be possible to grow with nothing at all coming to it and nothing persisting, and to waste away with nothing leaving it, and for the thing that grows not to persist.

30| But this must be preserved, for growth is assumed to be of just this kind. One might also raise the difficulty of what the thing that grows actually is: is it that to which something is added—for instance, if it makes the shin grow, the shin becomes greater—while that by which it grows, namely the nourishment, does not? Why, then, have not both grown? For both the thing that grows and the thing by which it grows become greater, as when you mix wine with water; for each of the two alike becomes more. Is it because in the one case the substance persists, but in the other, as with the nourishment, it does not? Since here too, in a mixture, we speak of whichever ingredient prevails—we say, for example, that it is wine; for the whole mixture performs the function of wine, not that of water. Similarly too in alteration: if a thing remains flesh, and remains what it is, but some affection belonging to it in its own right comes to be in it which did not exist before, then this has been altered; but the thing by which it has been altered has sometimes undergone nothing itself, and sometimes it too has been affected. But the altering agent, and the origin of the motion, is present within the thing growing and the thing being altered; for in these cases the mover is present in the thing itself, since even what has entered may at some point become greater, and so too the body that has drawn benefit from it—for instance, if what entered should turn into breath. But this, once affected in this way, has perished, and the mover is no longer present in it.

31| Since these points have been gone through with sufficient difficulty, we must also try to find a solution to the difficulty, while preserving both that the thing growing persists and grows by something coming to it, and wastes away by something leaving it, and further that any perceptible point whatever has become either greater or smaller, and that the body is not void, nor are there two magnitudes in the same place, nor does anything grow by means of something bodiless. We must grasp the cause by first distinguishing, first, that the non-homogeneous parts grow because the homogeneous parts grow (for each of them is composed out of these); and next, that flesh and bone and each part of that kind is twofold, just like the other things that have form in matter; for both the matter and the form alike are called flesh or bone. That any part whatever grows, and grows by something coming to it, is possible with respect to the form, but not with respect to the matter. One must conceive it as when someone measures out water with the same measure; for what results is always different water each time. In just this way the matter of the flesh grows, and something is not added to absolutely any and every part; rather, part flows out and part comes in; but with respect to the shape and the form, it is added to any part whatever.

32| This is more evident in the case of the non-homogeneous parts, for instance a hand, namely that it has grown in proportion; for there the matter, being distinct, is more evident than the form is in the case of flesh and the other homogeneous parts. That is why, in a corpse, it would seem more true that there is still flesh and bone than that there is still a hand and an arm. So that in one sense any part whatever of the flesh has grown, and in another sense it has not. For with respect to the form, something has come to any part whatever; but with respect to the matter, it has not. The whole, however, has become greater, since something has come to it—what is called nourishment, and is also its contrary—while it changes into the same form, as when something moist comes to something dry, and having come to it, changes and becomes dry itself; for in one sense the like grows by the like, in another sense by the unlike. One might raise the difficulty of what sort the thing must be by which growth occurs. It is clear that it must be that thing potentially—for instance, if it is flesh, potentially flesh. In actuality, then, it is something else; and this, having perished, has become flesh. It is not, then, this thing in its own right; for that would be coming-to-be, not growth; rather, it is by this that the thing growing grows. What, then, does it undergo from this, to be made to grow? It is mixed in, as when someone pours water onto wine, and the mixture is able to make wine.

33| And just as fire, having caught hold of what is combustible, so too in the thing that is growing and is actually flesh, the growth-producing power present in it, when potential flesh comes to it, makes that potential flesh into actual flesh. This happens, then, while the two exist together; for if separately, it would be coming-to-be. For it is possible to make fire in this way too, by putting logs onto a fire that already exists. But done this way it is growth; whereas when the logs themselves catch fire on their own, it is coming-to-be. As for quantity: the universal does not come to be, just as no animal comes to be that is neither man nor one of the particulars; but just as the universal does not come to be there, so quantity as such does not come to be here. What comes to be is flesh, or bone, or a hand, and the homogeneous parts belonging to these. So when something of a given quantity comes to it, it is not quantity that comes to be, but flesh of a given quantity. Insofar, then, as the combination of both—flesh, say, of a given quantity—exists potentially, in this respect the thing produces growth; for what comes to be must become both of that quantity and flesh; but insofar as it is only flesh, it nourishes; for in this respect nourishment and growth differ in their account. Hence a thing is nourished for as long as it is preserved, even while it is wasting away, but it does not always grow. And nourishment and growth are the same thing, though different in being: for insofar as what comes to it is potentially flesh of a given quantity, in this respect it is productive of the growth of flesh; but insofar as it is only potentially flesh, it is nourishment.

34| This form is without matter, being a sort of immaterial potentiality in matter. Now if further matter is added—matter that is itself potentially immaterial, and that likewise has quantity potentially—things thus formed will be greater while remaining immaterial. But if it can no longer act in this way, but—as water mixed in ever-greater quantity with wine eventually makes the wine watery, and finally just water—then there is a diminishing of the quantity, and the form no longer persists. 6 Since we must first speak about matter and the so-called elements—whether they exist or not, and whether each is everlasting or comes to be in some way, and if it comes to be, whether all things come to be from one another in the same way, or whether some one of them is primary—it is necessary first to speak about the matters now discussed without proper definition. For all who generate the elements, and those who generate the things composed of the elements, make use of separating-out and combining, and of acting and being acted on. Now combining is mixing; but how we mean things to be mixed has not been clearly defined. But surely there can be no altering

35| nor separating-out and combining, if nothing acts and nothing is acted on. For even those who posit several elements generate things by their acting on and being acted on by one another, and those who derive all things from one are also bound to speak of production, and Diogenes is right in saying that if all things did not come from one, there could be no acting and being acted on by one another—for instance the hot being cooled and this in turn being heated; for it is not heat and cold that change into one another, but plainly the underlying subject does. So wherever there is acting and being acted on, these must have some one underlying nature in common. Now it is not true to say that all things are of this sort, but only those in which there is acting by one another. But if we must study acting and being acted on and mixing, we must also study contact; for things cannot properly act on and be acted on by one another unless they are capable of touching one another, nor can they be mixed at all in the first place without touching in some way. So we must define these three things: what touching is, what mixing is, and what production is. Let us take this as our starting point: of necessity, whatever things admit of mixing must be capable of touching one another;

36| and if something acts while another is acted on, properly speaking, the same holds for these too. So we must speak first about touch. Now much as each of the other terms is said in many ways—some homonymously, others derived from one another and from a primary sense—so it is with touch as well. All the same, the term used in the strict sense belongs to things that have position. And position belongs to the same things as place; for to mathematical objects too we must assign touch and place in like manner, whether each of them is separated or exists in some other way. If, then, as was defined earlier, touching is having the extremities together, then those things would touch one another that, being determinate magnitudes and having position, have their extremities together at the same time. And since position belongs to whatever also has place, and the primary differentia of place is up and down and the like among

37| the opposites, everything that touches one another must have weight or lightness, or both, or one of the two. Such things are capable of being acted on and of acting; so it is clear that things are naturally suited to touch one another when, their magnitudes being divided, their extremities are together, they being capable of moving and being moved by one another. But since what moves does not move in the same way as what is moved—rather, the one, being itself in motion, must also move something else, while the other is unmoved—clearly we shall say the same about the agent too; for people say that what moves produces something, and what produces moves something. All the same, there is a difference, and we must draw a distinction; for not everything that moves can be said to produce, if we are going to oppose the agent to the patient. This belongs to things whose motion is an affection. An affection occurs only insofar as a thing is altered—for instance white and hot; but moving extends more widely than producing. This much, then, is clear: that in one sense moving things would touch the things moved, but in another sense not. But the definition of touching, taken generally, applies to things that have position, one being capable of moving and the other of being moved, and, with respect to each other, one capable of moving and the other capable of being moved, in cases where acting and being acted on occur. Now for the most part, what touches is touched by what it touches; for nearly all moving things move by moving whatever stands in their way, and in cases where this is necessary it also appears that what touches is touched by what it touches. But in another sense, we sometimes say that the mover touches only what is moved, while what is touched does not touch what touches it; but because things of the same kind move by being moved, it seems necessary that what touches be touched in turn. So if something moves while itself being unmoved, that thing would touch what is movable, but nothing would touch it; for we sometimes say that what causes us pain touches us, but we ourselves do not touch it. Let this, then, be our account of touch as it occurs among natural things.

38| 7 Next we must speak about acting and being acted on. We have inherited from our predecessors accounts opposed to one another. Most of them, at any rate, agree on this: that like is wholly unaffected by like, because neither of two like things is any more capable of acting than of being acted on than the other (for the same properties belong equally to things that are alike), while unlike and different things are naturally suited to act and be acted on by one another. Indeed, when a smaller fire is destroyed by a greater one, they say this happens on account of the opposition between them; for the much, they say, is opposite to the little. Democritus alone spoke differently from the rest; for he says that the agent and the patient are the same and alike; for, he says, it is not possible for things that are other and different to be acted on by one another—rather, even if things that are other do act on one another in some way, it is not insofar as they are other but insofar as some identical thing belongs to them—and this is how it comes about for them. These, then, are the views stated; and those who speak in this way seem to be saying things opposed to one another. The cause of this apparent conflict is that, though one ought to consider the whole matter, each of them happens to be speaking of only a part of it. For it is reasonable that the like, and what is in every way wholly undifferentiated, should not be acted on at all by the like (for why would one of them be any more capable of acting than the other?); and if it is possible for a thing to be acted on by its like, then it is possible for it to be acted on by itself as well; yet if this were so, nothing would be either indestructible or unmoved, given that like, insofar as it is like, is capable of acting—

39| for everything would move itself. And likewise for what is wholly other and in no way the same: nothing would happen to whiteness by a line, or to a line by whiteness, except perhaps incidentally—for instance, if it happens that the line is white or black; for things that are neither contraries nor composed of contraries do not remove one another from their own nature. But since it is not just anything that is naturally suited to be acted on and to act, but only things that either are contraries or contain a contrariety, it is necessary that the agent and the patient be alike and the same in genus, but unlike and contrary in species; for it is natural for body to be acted on by body, flavor by flavor, color by color, and in general the same-in-kind by the same-in-kind. The reason for this is that all contraries belong to the same genus. And contraries act on and are acted on by one another. So it is necessary that the agent and the patient be in one sense the same, and in another sense other and unlike one another. And since the patient and the agent are the same and alike in genus but unlike in species, and contraries are of this sort, it is clear that contraries, and things intermediate between contraries, are capable of acting on and being acted on by one another;

40| For corruption and generation, in a general sense, occur in these very cases. That is why it is reasonable enough that fire heats and the cold cools, and in general that what acts assimilates to itself what is affected: for what acts and what is affected are contraries, and generation is into the contrary, so that what is affected must necessarily change into what acts, since it is only in this way that generation will be into the contrary. And it is reasonable, then, that although they do not say the same thing, both parties nonetheless touch on the nature of the case. For we say that sometimes it is the substrate that is affected—for instance that the person is restored to health, or heated, or cooled, and so on in the same way for the rest—and sometimes that it is the cold that is heated, or the ailing thing that is restored to health; and both statements are true. And it is the same way, too, with what acts: sometimes we say that the person heats, sometimes that the hot thing heats; for in one sense it is the matter that is affected, in another sense the contrary. Those, then, who looked to the one case thought that what acts and what is affected must have something the same, while those who looked to the other cases thought the contrary. But the same account must be supposed to hold concerning acting and being affected as concerning moving and being moved.

41| For what moves is also spoken of in two ways: that in which the principle of motion resides is thought to move (since the principle is the first of the causes), and again so is the last thing, in relation to what is moved and to the coming-to-be. Likewise too with what acts: for we say both that the doctor heals and that the wine heals. Now nothing prevents the first mover from being unmoved in the motion; indeed in some cases this is even necessary; but the last thing always moves by being itself moved. And in the case of acting, the first thing is unaffected, but the last thing is itself affected as well: for whatever does not share the same matter acts without being affected—medicine, for instance, is like this, since medicine itself, in producing health, is in no way affected by the person being restored to health. But the food, in acting, is itself affected in some way too: for it is either heated or cooled or affected in some other way at the same time as it acts. Medicine, then, stands as a kind of principle, while the food is the last thing, the thing in actual contact. So whatever things have their form not in matter are, among things that act, unaffected, while whatever have it in matter are subject to being affected. For we say that the matter is, so to speak, alike the same for either of a pair of opposites, as being a kind of genus, while what is capable of being hot, when what can heat it is present and near, is necessarily heated.

42| That is why, as has been said, some things that act are unaffected and others are subject to being affected. And just as with motion, so it is with things that act: for there too the first mover is unmoved, and among things that act the first thing that acts is unaffected. Now the productive cause is a cause in the sense of that from which the principle of motion comes; but that for the sake of which is not productive. That is why health is not productive, except by a transference of the term: for when the agent is present, something comes to be that is affected, but when the states are already present, nothing further comes to be—it already is; and the forms and the ends are certain states, while matter, as matter, is subject to being affected. Fire, then, has heat in matter; but if there should be something hot that is separable, this could not be affected by anything. Now perhaps it is impossible for this to be separable; but if there are indeed some such things, then what has been said would be true in their case. What acting and being affected are, then, and to what things they belong, and why and how, let this be the way we have determined it.

43| 8 Let us say again in what way this can happen. Some think that each thing is affected by way of certain pores, when what acts, being last and most authoritative, enters in; and they say it is in this way that we see and hear and perceive by all the other senses as well, and further that a thing is seen through air and water and other transparent bodies because these have pores invisible on account of their smallness, but dense and set in rows, and that the more transparent bodies have more of them. Some, then, drew this distinction in certain cases—Empedocles, for instance, who says that not only in the case of things acting and being affected, but that things also mix whenever their pores are commensurate with one another; but it is Leucippus and Democritus who have determined the matter about all things most thoroughly, and in one systematic account, taking as their starting point what is in accordance with nature. For it seemed to some of the ancients that what is must of necessity be one and unmoved: for the void is not a thing that is, and motion would not be possible without a separately existing void; nor again could there be a plurality of things without something to separate them. And it makes no difference, they held, if someone supposes the whole is not continuous but touches itself while being divided, rather than saying there are many things and not one, and a void.

44| For if it is divisible everywhere, nothing is one, so that neither is there a plurality, but the whole is void; while if it is divisible in one part but not another, this looks like something contrived: for up to what point, and why, is one part of the whole in this state and full, while another is divided? And further, it is equally necessary to say that there is no motion. On these grounds, then, going beyond perception and disregarding it, on the ground that one ought to follow the argument instead, they say that the whole is one and unmoved, and some say unlimited as well; for a limit would be a limit against the void. These thinkers, then, declared themselves about the truth in this way and for these reasons; and while these conclusions seem to follow from the arguments, in point of fact to hold such opinions seems close to madness—for none of the mad are so far out of their senses as to think that fire and ice are one; it is only in the case of the fine and what appears so by habituation that some, on account of madness, think there is no difference. But Leucippus thought he had arguments which, being in agreement with perception, would not do away with either generation or corruption or motion or the multiplicity of the things that are.

45| Having conceded this much to appearances, but agreeing with those who establish the One that there could be no motion without void, he says that the void is not a thing that is ⟨he makes the void a non-being⟩, and that of what is, none of it is non-being. For what strictly is, is entirely full; but that what is such is not one, but there are unlimited things in multitude, invisible on account of the smallness of their bulk. These move about in the void (for there is void), and by combining they produce generation, and by separating, corruption. And they act and are affected wherever they happen to touch (for at that point they are not one), and by being put together and interwoven they generate; but from what is truly one, no multitude could come to be, nor from what are truly many could a one come to be, but this is impossible; rather, just as Empedocles and some others say things are affected through pores, so, on this view, every alteration and every case of being affected occurs in this way, dissolution and corruption coming about through the void, and increase likewise, by solid bodies slipping in besides. And Empedocles too is pretty much bound to say the same thing as Leucippus says: for there must be certain solid bodies, indivisible ones, unless the pores are everywhere continuous.

46| But this is impossible: for there will be nothing else solid apart from the pores, but everything will be void. It is necessary, then, that the things that touch be indivisible, and that what lies between them be void — what that man calls pores. This is also how Leucippus speaks about acting and being acted on. The ways, then, by which some things act and others are acted on are pretty much as stated; and about these matters, and how they speak of them, this much is clear, and it appears to follow fairly consistently with the positions they themselves hold. With the others it is less clear — for example, in what way there will be generation, corruption, and alteration for Empedocles is not clear. For the former hold that the primary bodies are indivisible, differing only in shape, and it is out of these primary bodies that things are composed and into these ultimate bodies that they are dissolved. But for Empedocles, it is evident that as regards the other things generation and corruption extend down to the elements; but how the accumulated bulk of these very elements themselves comes to be and perishes is neither clear, nor is it possible for him to say, since he does not even say that fire is an element — and likewise for all the others — as Plato writes in the Timaeus. For it makes this much difference from speaking in the same way as Leucippus: that the one speaks of solids as the indivisibles, the other of planes; and the one holds that each of the indivisible solids is bounded by an unlimited number of shapes, the other by a limited number, since both indeed say that they are indivisible and bounded by shapes.

47| From these principles, then, generations and separations would come about for Leucippus in two ways: through the void and through contact (for by this each thing is divisible), but for Plato only through contact — for he says that void does not exist. Now about the indivisible planes we have spoken in our earlier discussions; but about the indivisible solids, let a more extensive examination of what follows from them be set aside for now. Yet, to say a little by way of digression: it is necessary to say that each of the indivisibles is unaffected (for it cannot be acted on except through the void) and productive of no affection — for it cannot be either cold or hard. And yet this is absurd, to assign heat alone to the spherical shape; for it is necessary that the opposite too, the cold, belong to some other of the shapes. It is also absurd if these do belong — I mean heat and cold — while heaviness and lightness and hardness and softness do not belong; and yet Democritus says that each of the indivisibles is heavier in proportion to its excess, so that clearly it is also hotter. But if they are of this sort, it is impossible that they not be acted on by one another — for example, the mildly hot by the greatly excessive hot.

48| But further, if it is hard, it is also soft. Now the soft is already spoken of in terms of being acted on in some way — for what yields is soft. But it is also absurd if nothing belongs to it except shape alone; and equally absurd if something does belong, but only one thing — say, the one is cold, the other hot — for then their nature would not be a single one. And it is likewise impossible if more than one belongs to a single indivisible; for being indivisible, it will hold its affections in the same subject, so that if it is acted on — supposing it is cooled — it will also, in that very same subject, both do something and be affected in something else. And the same holds for the other affections too; for this follows in the same way both for those who call the indivisibles solids and for those who call them planes. For neither rarer nor denser can come to be, since there is no void within the indivisibles. Further, it is also absurd that small things should be indivisible but large ones not; for as things stand, it is reasonable that the larger break up more than the small — for some things are easily dissolved, such as the large ones, since they collide with many things — but why indivisibility in general should belong more to the small than to the large is unclear. Further, is the nature of all those solids one, or does one kind differ from another — as it would if some were of fire and others of earth in bulk?

49| For if the nature of them all is one, what is it that keeps them separate? Or why, when they touch, do they not become one, as water does when it touches water? For the latter is in no way different from the former. But if they are different, what are these differences? And it is clear that these must be laid down as the principles and causes of what happens, rather than the shapes. Further, being different in nature, they will either act or be acted on when they touch one another. Further, what is it that moves them? For if it is something else, then the moved thing is passive; but if each moves itself, then either it will be divisible — moving in one respect and being moved in another — or contraries will belong to the same thing in the same respect, and the matter will be one not merely in number but also in potentiality. Now as for those who say that affections come about through the boring of pores: if the affections occur even when the pores are completely filled, the pores are superfluous; for if a thing is affected in this way as a whole, it would be affected in the same way even without having pores, being itself continuous. Further, how is it possible for seeing-through to happen as they describe it? For it is not possible for sight to pass through transparent bodies by way of contact, nor through the pores, if each pore is full — for how will that differ from not having pores at all?

50| For everything will alike be full. But further, even if these pores are void, but must contain bodies within themselves, the same thing will result again. And if they are so small in size that no body at all can be received into them, it is absurd to suppose that a small pore is void while a large one is not, however large it may be — or to suppose that void means anything other than the room occupied by a body — so that it is clear that for every body there will be a void equal to it in bulk. In general, positing pores is superfluous; for if a body produces no effect by way of contact, it will not produce one by passing through the pores either; but if it does so by touching, then even with no pores present, some things will be acted on and others will act, among things naturally disposed toward one another in this way. It is clear from this, then, that to speak of pores in the way some suppose is either false or pointless. And since bodies are everywhere divisible, it is absurd to posit pores at all — for insofar as they are divisible, they can be separated.

51| 9 Let us state in what way generating, acting, and being acted upon belong to existing things, taking as our starting point the principle stated many times before. For if one thing is such potentially and another actually, then it is not the nature of the potential to be acted on in one respect and not in another, but wholly, to the extent that it is such — though less or more according as it is more or less such. And it is in this sense that one might rather speak of pores, as in mines, where continuous veins run through the region that is acted upon. Now each thing that is naturally unified and one is unaffected. And likewise things are unaffected when they do not touch either these things or others which they are naturally disposed to act on or be acted on by. I mean, for example, that fire heats not only by touching but even when it is at a distance — for fire heats the air, and the air heats the body, being naturally disposed to act and be acted on. But the view that a thing is acted on in one respect and not in another must be stated only after we have made a distinction at the outset. For if magnitude is not divisible in every respect, but there is some indivisible body or plane, then it would not be capable of being acted on in every respect, nor would anything be continuous at all; but if this is false and every body is divisible, then it makes no difference whether it has been divided but is still in contact, or is merely divisible;

52| For if a thing can be separated out along its seams, as some say, then even if it has not yet been divided, it will still be divided-in-principle; for it is capable of being divided; for nothing impossible results. But in general it is absurd that this should happen in this way only, by bodies being split apart; for this account does away with alteration, whereas we see the same continuous body being at one time fluid and at another solidified, and this is not something it undergoes by division and composition, nor by turning and inter-contact, as Democritus says; for it has not become solid out of fluid by being transposed or rearranged in position while remaining the same in nature. Nor do the hard and solidified bodies contain indivisible masses within them; rather, the whole thing alike is fluid, and at another time it is hard and solidified. Further, growth and diminution could not occur on this view either; for nothing will have come to be larger, if there is to be addition, unless the whole has changed, either by something being mixed in or by the thing changing in its own right. That there is such a thing as generating and producing, and coming-to-be and being-acted-on by one another, and in what way this is possible, and what some say is possible but is not, let this be determined in this way. It remains to consider mixture in the same manner of inquiry; for this was the third of the things proposed at the start.

53| We must examine what mixture is and what the mixed is, and to which existing things it belongs and how, and further whether there is such a thing as mixture at all or whether this is false; for some say it is impossible for one thing to be mixed with another. For, they say, if the things mixed still exist and have not been altered, they are no more mixed now than before, but are in the same condition as before; while if one of them has perished, they are not mixed, but one thing exists and the other does not, whereas mixture requires both to exist alike; and in the same way, even if both of the things combined have perished when they came together, they are not mixed, since things that do not exist at all cannot be said to be mixed. Now this argument seems to seek to distinguish how mixture differs from generation and corruption, and how the mixed differs from what is generated and what is destroyed; for clearly they must differ, if mixture is to exist at all. So once these points are made clear, the difficulties raised would be resolved. But in fact we do not say that the fuel is mixed with the fire, nor that it becomes mixed as it burns, neither with itself in its parts nor with the fire, but rather that the fire comes to be and the fuel is destroyed. In the same way we do not say that food is mixed with the body, nor that shape is mixed with the wax so as to shape the mass.

54| Nor can body and white, nor in general affections and states, be mixed with the things they belong to; for they are seen to be preserved unchanged. But indeed white and knowledge cannot be mixed either, nor can anything else that is not separable. But those who say that all things were once together and mixed do not put this well; for not everything is mixable with everything, but each of the things mixed must exist as something separable, and none of the affections is separable. Now since some existing things are potential and some actual, it is possible for the things mixed to be, in a sense, and also not to be: in actuality, the thing that has come to be out of them is one different thing, while each of the ingredients is still potentially what it was before being mixed, and has not perished; for this is what the argument raised as a difficulty earlier. It is evident that the things being mixed came together earlier out of a separated state and are capable of being separated again. So they neither persist in actuality, as body and white do, nor are they destroyed, neither one of them nor both; for their potentiality is preserved. Let these points, then, be set aside; but the difficulty connected with these must be dealt with in turn, namely whether mixture is something relative to perception. For when the things being mixed have been divided into such small parts, and placed alongside one another in such a way that each is not evident to perception, is the mixture then complete or not, but is it rather the case that any part whatsoever lies beside any other part of the things mixed?

55| Now it is said in that sense, for instance, that barley is mixed with wheat, when any grain of the one is placed beside any grain of the other. But if every body is divisible, then, given that there is such a thing as body being mixed with body with uniform parts throughout, any part whatsoever would have to come to lie beside any part whatsoever. But since it is not possible to divide down to the smallest parts, and composition is not the same thing as mixture but something different, it is clear that we should not say that the things mixed are mixed by being preserved in small pieces side by side. For then it will be composition, and not blending or mixture, and the part will not have the same ratio as the whole. But we say that, if anything is to be mixed, the thing mixed must be uniform throughout, and just as a part of water is water, so too is a part of the blended thing. But if mixture is a composition into small pieces, none of this will hold; instead, things will only be mixed relative to perception — and the same thing will be mixed for one person, if he does not have sharp sight, while for Lynceus nothing will be mixed — nor will it hold by division either, so that any part lies beside any part, for it is impossible to divide in that way. So either there is no such thing as mixture, or we must say how it is possible for it to come about again. There are, as we said, among existing things some that are active and some that are passive under these; now those things reciprocate with one another, whose matter is the same, and they are both active on one another and passive to one another.

56| But things whose matter is not the same act without themselves being acted upon. Of these there is no mixture; hence neither medicine nor health produces health by being mixed with bodies. Of the things that are active and passive, those that are easily divided, when many are combined with few, or great with small, do not produce a mixture but rather the growth of the dominant one; for the one changes over into the dominant thing, as, for instance, a drop of wine is not mixed with ten thousand measures of water, since its form is dissolved and it changes over into the water as a whole. But when they are somehow equal in their powers, then each changes over from its own nature into the dominant one, yet neither becomes the other, but something intermediate and common results. It is clear, then, that those things are mixable which have a contrariety among the things acting; for it is these that are indeed capable of being acted upon by one another. And small parts placed beside small parts are mixed more readily; for they displace one another more easily and quickly, whereas a large quantity acted on by a large quantity does this only over a long time. Hence things that are easily bounded, among things divisible and passive, are mixable — for these are easily divided into small parts, and this is what being easily bounded means — for instance, fluids are the most mixable of bodies; for the fluid is the most easily bounded of divisible things, provided it is not viscous.

57| For viscous things only make the resulting mass more numerous and larger. But when one of the two is passive only, or is so to an extreme degree, while the other is passive very faintly indeed, then the thing mixed from the two is either no greater or only slightly greater — which is what happens with tin and bronze. For some existing things stammer, so to speak, in relation to one another and waver between the two states; for they appear to be mixed only faintly in a way, and as if one were receptive and the other were the form. This is what happens in these cases: the tin, being as it were an affection without matter of the bronze, all but vanishes, and once mixed in, departs, having done nothing but color it. And this same thing happens in other cases too. It is clear, then, from what has been said, both that there is such a thing as mixture, and what it is, and why, and which of the existing things are mixable, since there are some things of such a kind as to be passive to one another and easily bounded and easily divided; for these need not have perished when mixed, nor still be simply the same as before, nor is their mixture a composition, nor a composition relative to perception; rather, the mixable is whatever is easily bounded and is passive and active, and mixable with something of the same kind (for the mixable is relative to something of the same name), and mixture is the unification of the mixables once they have been altered.

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