It is obvious also that the potency of merely doing a thing or having it done to one is implied in that of doing it or having it done well, but the latter is not always implied in the former: for he who does a thing well must also do it, but he who does it merely need not also do it well.
3 There are some who say, as the Megaric school does, that a thing ‘can’ act only when it is acting, and when it is not acting it ‘cannot’ act, (30) e. g. that he who is not building cannot build, but only he who is building, when he is building; and so in all other cases. It is not hard to see the absurdities that attend this view.
For it is clear that on this view a man will not be a builder unless he is building (for to be a builder is to be able to build), and so with the other arts. (35) If, then, it is impossible to have such arts if one has not at some time learnt and acquired them, and it is then impossible not to have them if one has not sometime lost them (either by forgetfulness or by some accident or by time; for it cannot be by the destruction of the object,7 for that lasts for ever), a man will not have the art when he has ceased to use it, and yet he may immediately build again; how then will he have got the art? And similarly with regard to lifeless things; nothing will be either cold or hot or sweet or perceptible at all if people are not perceiving it; so that the upholders of this view will have to maintain the doctrine of Protagoras.8 [1047a] But, (5) indeed, nothing will even have perception if it is not perceiving, i. e. exercising its perception. If, then, that is blind which has not sight though it would naturally have it, when it would naturally have it and when it still exists, the same people will be blind many times in the day—and deaf too.
Again, if that which is deprived of potency is incapable, (10) that which is not happening will be incapable of happening; but he who says of that which is incapable of happening either that it is or that it will be will say what is untrue; for this is what incapacity meant. Therefore these views do away with both movement and becoming. (15) For that which stands will always stand, and that which sits will always sit, since if it is sitting it will not get up; for that which, as we are told, cannot get up will be incapable of getting up. But we cannot say this, so that evidently potency and actuality are different (but these views make potency and actuality the same, and so it is no small thing they are seeking to annihilate), so that it is possible that a thing may be capable of being and not be, (20) and capable of not being and yet be, and similarly with the other kinds of predicate; it may be capable of walking and yet not walk, or capable of not walking and yet walk. And a thing is capable of doing something if there will be nothing impossible in its having the actuality of that of which it is said to have the capacity. (25) I mean, for instance, if a thing is capable of sitting and it is open to it to sit, there will be nothing impossible in its actually sitting; and similarly if it is capable of being moved or moving, or of standing or making to stand, or of being or coming to be, or of not being or not coming to be.
The word ‘actuality’, which we connect with ‘complete reality’, (30) has, in the main, been extended from movements to other things; for actuality in the strict sense is thought to be identical with movement. And so people do not assign movement to non-existent things, though they do assign some other predicates. e. g. they say that nonexistent things are objects of thought and desire, but not that they are moved; and this because, while ex hypothesi they do not actually exist, (35) they would have to exist actually if they were moved. For of non-existent things some exist potentially; but they do not exist, because they do not exist in complete reality. [1047b]
4 If what we have described9 is identical with the capable or convertible with it, evidently it cannot be true to say ‘this is capable of being but will not be’, (5) which would imply that the things incapable of being would on this showing vanish. Suppose, for instance, that a man—one who did not take account of that which is incapable of being—were to say that the diagonal of the square is capable of being measured but will not be measured, because a thing may well be capable of being or coming to be, and yet not be or be about to be. But from the premises this necessarily follows, (10) that if we actually supposed that which is not, but is capable of being, to be or to have come to be, there will be nothing impossible in this; but the result will be impossible, for the measuring of the diagonal is impossible. For the false and the impossible are not the same; that you are standing now is false, but that you should be standing is not impossible.
At the same time it is clear that if, when A is real, B must be real, (15) then, when A is possible, B also must be possible. For if B need not be possible, there is nothing to prevent its not being possible. Now let A be supposed possible. Then, when A was possible, we agreed that nothing impossible followed if A were supposed to be real; and then B must of course be real. (20) But we supposed B to be impossible. Let it be impossible, then. If, then, B is impossible, A also must be so. But the first was supposed impossible; therefore the second also is impossible. If, then, A is possible, B also will be possible, if they were so related that if A is real, B must be real. If, then, A and B being thus related,10 B is not possible on this condition,11 (25) A and B will not be related as was supposed.12 And if when A is possible, B must be possible, then if A is real, B also must be real. For to say that B must be possible, if A is possible, means this, that if A is real both at the time when and in the way in which it was supposed capable of being real, B also must then and in that way be real. (30)
5 As all potencies are either innate, like the senses, or come by practice, like the power of playing the flute, or by learning, like artistic power, those which come by practice or by rational formula we must acquire by previous exercise but this is not necessary with those which are not of this nature and which imply passivity.
Since that which is ‘capable’ is capable of something and at some time and in some way (with all the other qualifications which must be present in the definition), (35) and since some things can produce change according to a rational formula and their potencies involve such a formula, while other things are non-rational and their potencies are non-rational, and the former potencies must be in a living thing, while the latter can be both in the living and in the lifeless; as regards potencies of the latter kind, when the agent and the patient meet in the way appropriate to the potency in question, the one must act and the other be acted on, but with the former kind of potency this is not necessary. [1048a] For the non-rational potencies are all productive of one effect each, but the rational produce contrary effects, (5) so that if they produced their effects necessarily they would produce contrary effects at the same time; but this is impossible. There must, then, (10) be something else that decides; I mean by this, desire or will. For whichever of two things the animal desires decisively, it will do, when it is present, and meets the passive object, in the way appropriate to the potency in question. Therefore everything which has a rational potency, when it desires that for which it has a potency and in the circumstances in which it has the potency, must do this. (15) And it has the potency in question when the passive object is present and is in a certain state; if not it will not be able to act. (To add the qualification ‘if nothing external prevents it’ is not further necessary; for it has the potency on the terms on which this is a potency of acting, and it is this not in all circumstances but on certain conditions, among which will be the exclusion of external hindrances; for these are barred by some of the positive qualifications. (20)) And so even if one has a rational wish, or an appetite, to do two things or contrary things at the same time, one will not do them; for it is not on these terms that one has the potency for them, nor is it a potency of doing both at the same time, since one will do the things which it is a potency of doing, on the terms on which one has the potency.
6 Since we have treated13 of the kind of potency which is related to movement, (25) let us discuss actuality—what, and what kind of thing, actuality is. For in the course of our analysis it will also become clear, with regard to the p
otential, that we not only ascribe potency to that whose nature it is to move something else, or to be moved by something else, either without qualification or in some particular way, but also use the word in another sense, which is the reason of the inquiry in the course of which we have discussed these previous senses also. (30) Actuality, then, is the existence of a thing not in the way which we express by ‘potentially’; we say that potentially, for instance, a statue of Hermes is in the block of wood and the half-line is in the whole, because it might be separated out, and we call even the man who is not studying a man of science, if he is capable of studying; the thing that stands in contrast to each of these exists actually. (35) Our meaning can be seen in the particular cases by induction, and we must not seek a definition of everything but be content to grasp the analogy, that it is as that which is building is to that which is capable of building, and the waking to the sleeping, and that which is seeing to that which has its eyes shut but has sight, and that which has been shaped out of the matter to the matter, and that which has been wrought up to the unwrought. [1048b] Let actuality be defined by one member of this antithesis, (5) and the potential by the other. But all things are not said in the same sense to exist actually, but only by analogy—as A is in B or to B, C is in D or to D; for some are as movement to potency, and the others as substance to some sort of matter.
But also the infinite and the void and all similar things are said to exist potentially and actually in a different sense from that which applies to many other things, (10) e. g. to that which sees or walks or is seen. For of the latter class these predicates can at some time be also truly asserted without qualification; for the seen is so called sometimes because it is being seen, sometimes because it is capable of being seen. But the infinite does not exist potentially in the sense that it will ever actually have separate existence; it exists potentially only for knowledge. (15) For the fact that the process of dividing never comes to an end ensures that this activity exists potentially, but not that the infinite exists separately.
Since of the actions which have a limit none is an end but all are relative to the end, e. g. the removing of fat, or fat-removal, (20) and the bodily parts themselves when one is making them thin are in movement in this way (i. e. without being already that at which the movement aims), this is not an action or at least not a complete one (for it is not an end); but that movement in which the end is present is an action. e. g. at the same time we are seeing and have seen, are understanding and have understood, are thinking and have thought (while it is not true that at the same time we are learning and have learnt, (25) or are being cured and have been cured). At the same time we are living well and have lived well, and are happy and have been happy. If not, the process would have had sometime to cease, as the process of making thin ceases: but, as things are, it does not cease; we are living and have lived. Of these processes, then, we must call the one set movements, and the other actualities. For every movement is incomplete—making thin, learning, walking, building; these are movements, and incomplete at that. For it is not true that at the same time a thing is walking and has walked, (30) or is building and has built, or is coming to be and has come to be, or is being moved and has been moved, but what is being moved is different from what has been moved, and what is moving from what has moved. But it is the same thing that at the same time has seen and is seeing, or is thinking and has thought. The latter sort of process, then, I call an actuality, and the former a movement.
7 What, and what kind of thing, the actual is, (35) may be taken as explained by these and similar considerations. But we must distinguish when a thing exists potentially and when it does not; for it is not at any and every time. [1049a] e. g. is earth potentially a man? No—but rather when it has already become seed, and perhaps not even then. It is just as it is with being healed; not everything can be healed by the medical art or by luck, but there is a certain kind of thing which is capable of it, and only this is potentially healthy. And (1) the delimiting mark of that which as a result of thought comes to exist in complete reality from having existed potentially is that if the agent has willed it it comes to pass if nothing external hinders, (5) while the condition on the other side—viz. in that which is healed—is that nothing in it hinders the result. It is on similar terms that we have what is potentially a house; if nothing in the thing acted on—i. e. in the matter—prevents it from becoming a house, (10) and if there is nothing which must be added or taken away or changed, this is potentially a house; and the same is true of all other things the source of whose becoming is external. And (2) in the cases in which the source of the becoming is in the very thing which comes to be, a thing is potentially all those things which it will be of itself if nothing external hinders it. e. g. the seed is not yet potentially a man; for it must be deposited in something other than itself and undergo a change. But when through its own motive principle it has already got such and such attributes, (15) in this state it is already potentially a man; while in the former state it needs another motive principle, just as earth is not yet potentially a statue (for it must first change in order to become brass).
It seems that when we call a thing not something else but ‘thaten’—e. g. a casket is not ‘wood’ but ‘wooden’, and wood is not ‘earth’ but ‘earthen’, (20) and again earth will illustrate our point if it is similarly not something else but ‘thaten’—that other thing is always potentially (in the full sense of that word) the thing which comes after it in this series. e. g. a casket is not ‘earthen’ nor ‘earth’, but ‘wooden’; for this is potentially a casket and this is the matter of a casket, wood in general of a casket in general, and this particular wood of this particular casket. And if there is a first thing, which is no longer, in reference to something else, called ‘thaten’, (25) this is prime matter; e. g. if earth is ‘airy’ and air is not ‘fire’ but ‘fiery’, fire is prime matter, which is not a ‘this’. For the subject or substratum is differentiated by being a ‘this’ or not being one; i. e. the substratum of modifications is, e. g., a man, i. e. a body and a soul, (30) while the modification is ‘musical’ or ‘pale’. (The subject is called, when music comes to be present in it, not ‘music’ but ‘musical’, and the man is not ‘paleness’ but ‘pale’, and not ‘ambulation’ or ‘movement’ but ‘walking’ or ‘moving’—which is akin to the ‘thaten’.) Wherever this is so, then, the ultimate subject is a substance; but when this is not so but the predicate is a form and a ‘this’, (35) the ultimate subject is matter and material substance. And it is only right that ‘thaten’ should be used with reference both to the matter and to the accidents; for both are indeterminates. [1049b]
We have stated, then, when a thing is to be said to exist potentially and when it is not.
8 From our discussion of the various senses of ‘prior’,14 it is clear that actuality is prior to potency. (5) And I mean by potency not only that definite kind which is said to be a principle of change in another thing or in the thing itself regarded as other, but in general every principle of movement or of rest. For nature also is in the same genus as potency; for it is a principle of movement—not, (10) however, in something else but in the thing itself qua itself. To all such potency, then, actuality is prior both in formula and in substantiality; and in time it is prior in one sense, and in another not.
(1) Clearly it is prior in formula; for that which is in the primary sense potential is potential because it is possible for it to become active; e. g. I mean by ‘capable of building’ that which can build, (15) and by ‘capable of seeing’ that which can see, and by ‘visible’ that which can be seen. And the same account applies to all other cases, so that the formula and the knowledge of the one must precede the knowledge of the other.
(2) In time it is prior in this sense: the actual which is identical in species though not in number with a potentially existing thing is prior to it. I mean that to this particular man who now exists actually and to the corn and to the seeing subject the matter and the
seed and that which is capable of seeing, (20) which are potentially a man and corn and seeing, but not yet actually so, are prior in time; but prior in time to these are other actually existing things, from which they were produced. For from the potentially existing the actually existing is always produced by an actually existing thing, e. g. man from man, musician by musician; there is always a first mover, (25) and the mover already exists actually. We have said in our account of substance15 that everything that is produced is something produced from something and by something, and that the same in species as it.
This is why it is thought impossible to be a builder if one has built nothing or a harper if one has never played the harp; for he who learns to play the harp learns to play it by playing it, (30) and all other learners do similarly. And thence arose the sophistical quibble, that one who does not possess a science will be doing that which is the object of the science; for he who is learning it does not possess it. But since, of that which is coming to be, some part must have come to be, (35) and, of that which, in general, is changing, some part must have changed (this is shown in the treatise on movement16), he who is learning must, it would seem, possess some part of the science. [1050a] But here too, then, it is clear that actuality is in this sense also, viz. in order of generation and of time, prior to potency.
The Basic Works of Aristotle (Modern Library Classics) Page 115
