Lecture 14 — Problems on the nature of that by which something grows.

We must therefore come to closer quarters with the subject of our inquiry. We must grapple' with it (as it were) from its beginning, and determine the precise character of the growing and diminishing whose causes we are investigating.

It is evident (i) that any and every part of the growing thing has increased, and that similarly in diminution every part has become smaller: also (ii) that a thing grows by the accession, and diminishes by the departure, of something.

Hence it must grow by the accession either (a) of something incorporeal or (b) of a body. Now, if (a) it grows by the accession of something incorporeal, there will exist separate a void: but (as we have stated before)' is impossible for a matter of magnitude to exist 'separate'. If, on the other hand (b) it grows by the accession of a body, there will be two bodies—that which grows and that which increases it—in the same place: and this too is impossible.

But neither is it open to us to say that growth or diminution occurs in the way in which e.g. air is generated from water. For, although the volume has then become greater, the change will not be growth, but a coming-to-be of the one—viz. of that into which the change is taking place—and a passing-away of the contrasted body. It is not a growth of either. Nothing grows in the process; unless indeed there be something common to both things (to that which is coming-to-be and to that which passed-away), e.g. 'body', and this grows. The water has not grown, nor has the air: but the former has passed-away and the latter has come-to-be, and—if anything has grown—there has been a growth of 'body.' Yet this too is impossible. For our account of growth must preserve the characteristics of that which is growing and diminishing. And these characteristics are three: (i) any and every part of the growing magnitude is made bigger (e.g. if flesh grows, every particle of the flesh gets bigger), (ii) by the accession of something, and (iii) in such a way that the growing thing is preserved and persists. For whereas a thing does not persist in the processes of unqualified coming-to-be or passing-away, that which grows or 'alters' persists in its identity through the 'altering' and through the growing or diminishing, though the quality (in 'alteration') and the size (in growth) do not remain the same. Now if the generation of air from water is to be regarded as growth, a thing might grow without the accession (and without the persistence) of anything, and diminish without the departure of anything—and that which grows need not persist. But this characteristic must be preserved: for the growth we are discussing has been assumed to be thus characterized.

One might raise a further difficulty. What is 'that which grows'? Is it that to which something is added? If, e.g. a man grows in his shin, is it the shin which is greater—but not that 'whereby' he grows, viz. not the food? Then why have not both 'grown'? For when A is added to B, both A and B are greater, as when you mix wine with water; for each ingredient is alike increased in volume.

Perhaps the explanation is that the substance of the one remains unchanged, but the substance of the other (viz. of the food) does not. For indeed, even in the mixture of wine and water, it is the prevailing ingredient which is said to have increased in volume. We say, e.g. that the wine has increased, because the whole mixture acts as wine but not as water. A similar principle applies also to 'alteration'. Flesh is said to have been 'altered' if, while its character and substance remain, some one of its essential properties, which was not there before, now qualifies it: on the other hand, that 'whereby' it has been 'altered' may have undergone no change, though sometimes it too has been affected. The altering agent, however, and the originative source of the process are in the growing thing and in that which is being 'altered': for the efficient cause is in these. No doubt the food, which has come in, may sometimes expand as well as the body that has consumed it (that is so, e.g. if, after having come in, a food is converted into wind), but when it has undergone this change it has passed-away: and the efficient cause is not in the food.

97. After discussing growth from the viewpoint of that which grows, the Philosopher here inquires into that by which something grows.

First he states his intention (320b34) and says that, since it is of the notion of growth that it be an addition of magnitude, what would seem to be more appropriately taken up in the present inquiry, as being more difficult and affording some beginning for the question, would be to inquire into the nature of that by which something grows or diminishes, so as to find appropriate causes for growth and diminution.

Second, at it is evident (321a2; [98]), he pursues his inquiry:

first, he states the main question;

second, in the course of this investigation he proposes another question, at one might raise a further difficulty (321a29; [102]);

third, he resolves the main question, at we have now developed (321b10; [104]).

About the first he does three things:

first, he proposes two suppositions;

second, he raises the doubt, at hence it must grow (321a5; [99]);

third, he excludes an objection, at but neither is it open to us (321a9; [100]).

98. The first supposition which he proposes (321a2), therefore, is this: When something grows, every part of it grows; likewise, in diminution, every part of that which is diminished is seen to have become smaller. The reason for this is apparent from what is said in Physics V. For that whose part is being moved is said to be moved with respect to a part and not absolutely, as for example, a man whose hand has been wounded is said to be wounded with respect to a part.

But in order that a thing be moved per se and absolutely, it is required that each and every part be moved. This must also be observed in growth and in all other motions, as our senses testify.

The second supposition is that whatever grows, grows by reason of something added to it; similarly, something is diminished by reason of something's leaving it. The reason for this is that things must be reduced into act by something already in act. Hence, that which is in potency to a greater quantity is brought into the act of that quantity by something that has that quantity in act. And this is what is added to the thing that grows.

99. Then, at hence it must grow (321a5), he presents the difficulty which follows from these two suppositions. For if every part of a growing thing has to grow and all growth is produced by the addition of something, then something has to be added to each and every part of the growing thing. Therefore whatever is added, by which a thing is said to grow, has to be either incorporeal or corporeal. If it should be said to be incorporeal, then it follows that the common [base] of all generable and corruptible things, namely, first matter, exists separated from all corporeal quantity. But, as was shown above, it is impossible for matter to be separated from magnitude. Consequently, that by which something grows cannot be incorporeal. Moreover, if it were incorporeal, it would not be quantified in act and consequently it would not make the thing to which it was added larger according to quantity.

On the other hand, if that by whose addition something grows should be said to be corporeal, it would follow that two bodies are occupying the same place at the same time, namely, the body which is increased and the body added which does the increasing. For it cannot be held that the body increased and the body which increases are set separately side by side, because addition must be made to each and every part of the increased body, as follows from the suppositions stated above. But this also is impossible, namely, that two bodies occupy the same place at the same time. Consequently, an impossibility follows from both alternatives.

100. Then, at but neither is it open to us (321a9), he rejects a certain solution. For someone could say that growth occurs without anything being added, just as, when air is generated from water, there appears to be a certain growth, since a greater quantity is produced. But that is not the way growth and decrease take place. For such a change [as that mentioned in the example) is not growth. It is rather the generation of that into which the change is made, namely, air, and the corruption of that which is changed, namely, water, which is contrary to air, by the contrariety, namely, of coldness and warmth. It cannot therefore be called growth either of air or of water.

But if it is not growth of either, it will perhaps be growth of that which is common to both (if there be such a thing) as, for example, of body, which seems to be common to air and water, so that it could be said that the water has not grown nor the air, since the water has been corrupted and the air generated, but that it is body that grows, if anything has grown there. But this is impossible. For in order that something be said to grow, those things must be accounted for which pertain to what grows and diminishes. These are three.

The first of these, which was also posited above, is that each part of the magnitude which grows must become larger—for example, if flesh is increased, each part must become larger.

Second, as was also posited above, the thing must grow by something's being added.

The third requirement is something which he now posits for the first time and it is that the thing increased be preserved and remain in its being. For, since generation and corruption are changes with respect to substance, when a thing is generated or corrupted absolutely, its substance does not remain.

But other changes are not with respect to substance, but with respect to things that occur to the substance — for example, changes regarding quantity or quality. Therefore, when something is altered, or grows or is diminished, that which grows or is altered remains the same in number as to substance, but here, namely, in alteration, the passion does not remain the same, and here, namely, in growth and decrease, the magnitude does not remain the same, but becomes larger or smaller. If, therefore, the aforesaid change, by which out of water air is produced, were growth, two things contrary to the aforesaid suppositions would follow.

First of all something would grow without anything's being added and be diminished without anything's leaving. The other is that that which grows does not remain, since neither does the water remain nor does body, which appears to be common, remain the same in number. Hence he designedly said above, if there be such a common thing—since, namely, nothing which is being in act, remaining the same in number as to substance, is common to that which is corrupted and generated. But it is necessary for the aforesaid suppositions to be accounted for in everything which grows—it being supposed, in the manner of a principle, that growth is a change of the sort that has been stated above.

101. But nothing seems to prevent something from growing without anything's being added. For in Physics IV the Philosopher proves that just as a thing becomes whiter not by some other white's being added to it, but by the previous whiteness' being intensified, namely, through the subject's being reduced too a state of more perfect whiteness, so also something can become larger without the addition of some body possessing magnitude, through the matter, which previously was subject to small dimensions, being afterward made subject to large dimensions. For the same thing is the subject of large and small and of white and black. And this is clearly apparent in rarefaction, for rarefaction takes place not only when there is a change of species, as when air is generated from water, which Aristotle speaks about here, but also when the same species remains, as when air is rarified or condensed.

However, it should be replied that such a change cannot be properly called "growth," but is alteration. For it takes place in terms of a change of passible qualities, namely, of rarity and density, with a variation of quantity being consequent upon this—just as when, as the result of a motion with respect to place, there is a change in motion according to right or left; this is nevertheless not referred to as a motion according to position—since the change of position is consequent upon the changing of place.

102. Then, at one might raise a further difficulty (321a29), before solving the aforesaid difficulty, he raises another question.

First, he proposes the question;

second, he solves it, at perhaps the explanation (321a34; [103]).

He says therefore first (321a29) that, since a thing grows by the addition of something, the question still remains as to what it is that is increased: whether only that to which something is added, but not what is added, or whether both are increased. For example, if something, namely, food, is added to the leg of an animal, does the leg grow and become larger while the food which is brought in and added does not grow but causes growth? Why have not both grown? For both become larger, both what is added and that to which it is added, just as, when water is mixed with wine, both are seen to be increased, because both become larger in the same way.

103. Then, at perhaps the explanation (321a34), he answers this question in the light of what has been set down above, namely, that the thing which grows must remain the same in substance. Therefore the one is said to be increased and not the other, because the substance of that, namely, the leg, to which addition is made, remains, while the substance of what is added, namely, the food, does not remain—for the food is converted into the substance of what is nourished and increased. But because in the objection mention of a mixture was made, he shows that the same is true in a mixture. For that whose substance remains is said to be dominant in the mixture—as we say something to be wine, when only a little, water is added to much wine. And this appears from the proper operation, which is an evident sign of the species—for the whole mixture performs the operation of wine, namely, by warming and giving strength, and does not do the work of water. A like situation occurs in alteration: for if the flesh remains in its substance and what something is, i.e., its essence or species, and some passion, of the number of per se accidents, occurs to it, which was previously not present, that which remains is said to be altered. Similarly, that which grows must remain.

But that by which something is altered, namely, that which alters, sometimes undergoes no change, either in quality or substance, as occurs in thins that act and do not undergo, such as heavenly bodies; but sometimes that which alters itself-undergoes and is changed, as occurs in the lower bodies, which mutually act and undergo, as will be manifest later. However, in the motion of growth, the alterating power, and that which is the starting-point of motion, is on the part of that which grows—which, however, alters in a way that also involves its own alteration. For in things that grow, exists a principle of the motion of growth, namely to alter and convert the food which is added. If this were not so, the food entering the body would thus be generated greater and would take into its nature the body into which it was entering—as, for example, when spirit, i.e., air, enters a bladder and makes it larger, or when spirit, i.e., a soul enters a body and conforms it to itself. But that is not what happens. Rather the food enters the body and, after being acted upon by the body of the animal, is converted into the body of the animal; and the origiuative source of this change is not in that which is added, but in that to which the addition is made.