LESSON 3

Rejection of the View That a Thing Has Potency Only When It

Is Acting. Rejection of the View That All Things Are Possible

  Chapters 3 & 4: 1046b 29-1047b 30

             751. There are some, such as the members of the Megaric school, who say that a thing has a potency for acting only when it is acting, and that when it is not acting it does not have this potency; for example, one who is not building does not have the power of building, but only one who is building when he is building; and it is the same in other cases.

             752. It is not difficult to see the absurd consequences of this position. For it is evident, according to this view, that a man will not be a builder if he is not building, because to be a builder is to be able to build. The same is true in the case of the other arts. Therefore, if it is impossible to have such arts unless one has at some time learnt and acquired them, and if it is impossible not to have them unless one has at some time lost them (either through forgetfulness or through some change or through the passage of time; for this cannot occur as a result of the object being destroyed, since it always exists), when one will have ceased to use an art he will not have it; and yet he will be able to build forthwith, thus somehow getting it back again.

             753. And the same thing will be true in the case of non-living things; for neither the cold nor the hot nor the sweet nor the bitter nor any sensible thing will exist in any way at all if they are not being sensed. Hence they will have to maintain the theory that Protagoras did.

             754. In fact nothing will have senses unless it is sensing or acting. Therefore, if that is blind which does not have the power of sight, though it is designed by nature to have it, and when it is designed by nature to have it, and so long as it exists, the same persons will be blind many times during the day; and deaf as well.

             755. Further, if what is deprived of a potency is incapable, it will be impossible for that to come into being which has not yet been generated; but he who says that what cannot possibly be generated either is or will be, is in error; for this is what impossible or incapable means. Hence these theories do away with both motion and generation; for what is standing will always stand, and what is sitting will always sit, because if it is sitting it will not get up, since it is impossible for anything to get up which has no possibility of doing so.

             756. Therefore, if it is impossible to maintain this, it is evident that potency and actuality are distinct. But these views make potency and actuality the same, and for this reason it is no small thing which they seek to destroy. Hence it is possible for a thing to be capable of being and yet not be, and for a thing not to be and yet be capable of being. And it is similar in the case of the other categories; for example, a thing may be capable of walking and yet not walk, and be capable of not walking and yet walk.

             757. Moreover, a thing has a potency if there is nothing impossible in its having the actuality of that of which it is said to have the potency. I mean, for example, that if a thing is capable of sitting, and it turns out to be sitting, there will be nothing impossible in its having a sitting position; and it is similar if it is capable of being moved or of moving something, or of standing or causing a thing to stand, or of being or coming to be, or of not being or not coming to be.

             758. And the word actuality, which is combined with entelechy, is extended chiefly from motion to other things; for actuality seems to be identified mainly with motion. And for this reason they do not assign motion to non-existent things, but they do assign the other categories. For example, non-existent things are considered the objects of intellect and desire but not to be in motion. And the reason is that they would have to exist actually even though they did not exist actually; for some non-existent things are potential. Yet they do not exist, because they do not exist in complete actuality.

Chapter 4

             759. Now if what has been called potential or possible is such because something follows from it, it is evident that it cannot be true to say that a thing is possible but will not be, because things which cannot possibly be would then disappear. An example would be if someone, thinking that nothing is impossible, were to affirm that it is possible for the diagonal of a square to be commensurate, even though it is not commensurate; because nothing prevents a thing that is capable of being or of coming to be from not being or not coming to be. But this conclusion necessarily follows from the things laid down above. And if we suppose that which is not but is capable of being, to be or to have come into being, nothing would be impossible. But in this case something impossible will occur; for it is impossible that a diagonal be commensurate. For to be false and to be impossible are not the same; for while it is false that you are now standing, it is not impossible.

             760. And at the same time it is evident that, if when A exists B must exist, then if A is possible B must be possible; for if it is not necessary that B be possible, there is nothing to prevent its not being possible. Therefore, let A be possible. And if A is possible, then when A is possible, if A is assumed to exist, nothing impossible follows, but B necessarily exists. But this was supposed to be impossible. Therefore, let B be impossible. Then if B must be impossible, A must be so. But the first was supposed to be impossible; therefore so also is the second. Hence, if A is possible, B will be possible also, i.e., if they are so related that, when A exists, B must exist. Therefore, if when A and B are so related, B is not possible, then A and B will not be related in the way supposed. On the other hand, if, when A is possible, B must be possible, then if A exists, B must exist. For to say that B must be possible if A is possible, means that, if A exists both when it exists and in the way in which it is possible for it to exist, then B must also exist and exist in that way.

COMMENTARY

             1795. Having compared one kind of potency with another in the above discussion, here the Philosopher begins to explain how potency and actuality are found in the same subject. This is divided into two parts. In the first (751:C 1795) he rejects the false opinions of some men. In the second (761:C 1815) he establishes the truth ("And since among").

             The first is divided into two parts. In the first part he rejects the opinion of those who said that a thing is possible or potential only when it is in a state of actuality. In the second part (759:C 1810) he rejects the opinion of those who maintain the reverse of this: that all things are potential or possible, even though they are not in a state of actuality ("Now if what").

             In regard to the first he does two things. First, he rejects the erroneous opinion referred to. Second (757:C 1804), he explains what it is to be potential or possible, and what it is to be actual ("Moreover, a thing").

             In regard to the first he does three things. First, he gives this opinion. Second (752:C 1796), he destroys it ("It is not difficult"). Third (756:C 1803), he draws his intended conclusion ("Therefore, if it").

             He accordingly says, first, that some said that a thing is in a state of potency or capability only when it is acting; for example, a man who is not actually building is incapable of building, but he is capable of building only when he is actually building; and they speak in a similar way about other things. The reason for this position seems to be that they thought that all things come about necessarily because of some connection between causes. Thus if all things come about necessarily, it follows that those things which do not, are impossible.

             1796. It is not difficult (752).

             Then he adduces arguments against the above opinion, and these reduce it to its absurd consequences. The first is as follows: to be building is to have the power or capability of building. Therefore, if no one has the power or capability of acting except when he is acting, no one is a builder except when he is building. And the same thing will be true of the other arts; for all arts are certain capabilities or potencies, as has been pointed out (746:C 1786). It follows, then, that no one will have an art except when he is exercising it.

             1797. But this is shown to be impossible if two assumptions are made. The first is this: if someone did not at first have an art, it would be impossible for him to have it later unless he had learned it or acquired it in some way, i.e., by discovery.

             1798. The second assumption is that if someone had an art it would be impossible for him not to have the same art later unless he lost it in some way, either through forgetfulness or through some illness or through the passage of a long time during which the knowledge was not exercised; for this is the cause of forgetfulness. Now it cannot be that someone should lose an art as a result of the destruction of its object, as it sometimes happens that true knowledge is lost when a thing is changed; for example, when someone makes a true judgment that Socrates is sitting, his true judgment is destroyed when Socrates stands up. But this cannot be said about an art; for an art is not a knowledge of what exists, but of what is to be made; and so long as the matter from which an art can produce something continues to exist, the object of that art always exists. Hence an art cannot be lost when its object is destroyed, except in the ways mentioned.

             1799. Now from these two assumptions the Philosopher argues as follows: if a man does not have an art except when he is exercising it, then when he begins to exercise it he has it anew. Therefore he must either have learned it or acquired it in some other way. And similarly when he ceases to exercise an art it follows that he lacks that art, and thus he loses the art which he previously had either through forgetfulness or through some change or through the passage of time. But both of these are clearly false; and therefore it is not true that someone has a potency only when he is acting.

             1800. And the same (753).

             Here he gives the second argument, which now has to do with the irrational principles present in non-living things, namely, hot and cold, sweet and bitter, and other qualities of this kind, which are active principles changing the senses and thus are potencies. Now if potency is present in a thing only when it is acting, it follows that nothing is hot or cold, sweet or bitter, and so forth, except when it is being sensed through a change in the senses. But this is clearly false; for if it were true it would follow that Protagoras' opinion would be true, since he said that all the properties and natures of things have existence only in being sensed and in being thought. And from this it would follow that contradictories would be true at the same time, since different men have contradictory opinions about the same thing. Now the Philosopher argued dialectically against this position above in Book IV (343:C 636). Therefore it is false that potency exists only when there is activity.

             1801. In fact nothing (754).

             Here he gives the fourth argument, which is as follows: sense is a kind of potency. Therefore, if potency exists only when there is activity, it follows that a man has sensory power only when he is sensing, for example, the power of sight or hearing. But one who does not have the power of sight although he is naturally disposed to have it is blind; and one who does not have the power of hearing is deaf. Hence he will be blind and deaf many times on the same day. But this is clearly false, for a blind man does not afterwards regain sight nor a deaf man hearing.

             1802. Further, if what (755).

             Here he gives the fourth argument, which is as follows: it is impossible for a thing to act which does not have the power to act. Therefore, if one has a potency or power only when he is acting, it follows that when he is not acting it is impossible for him to act. But whoever says that something incapable of happening either is or will be, is mistaken. This is evident from the meaning of the word impossible; for the impossible is said to be false because it cannot happen. It follows, then, that something which is not is incapable of coming to be in any way. And thus potency so understood will do away with motion and generation, because one who is standing will always stand, and one who is sitting will always sit. For if anyone is sitting, he will never stand afterwards, because so long as he is not standing he does not have the power to stand. Hence it is impossible for him to stand, and consequently it is impossible for him to get up. Similarly what is not white will be incapable of being white, and thus could not be made white. The same holds true in the case of all other things.

             1803. Therefore, if (756).

             He draws his intended conclusion, saying that, if the absurdities mentioned above cannot be admitted, it is obvious that potency and actuality are distinct. But those who hold the foregoing position make potency and actuality the same insofar as they say that something has potency only when it is in a state of actuality. And from this it is evident that they wish to remove from nature something of no little importance, for they eliminate motion and generation, as has been stated (755:C 1802). Hence, since this cannot be admitted, it is obvious that something is capable of being which yet is not, and that something is capable of not being which yet is. And "it is similar in the case of the other categories," or predicaments, because it is possible from someone who is not walking to walk, and conversely it is possible from someone who is walking not to walk.

             1804. Moreover, a thing (757).

             Here he explains what it is to be potential and what it is to be actual. First, he explains what it is to be potential. He says that that is said to be potential from which nothing impossible follows when it is assumed to be actual; for example, if one were to say that it is possible for someone to sit if nothing impossible follows when he is assumed to sit. And the same holds true of being moved and of moving something, and other cases of this kind.

             1805. And the word "actuality" (758).

             Second, he explains what it is to be actual. He says that the word actuality is used to signify entelechy and perfection, namely, the form, and other things of this kind, as any action at all, is derived properly from motion, so far as the origin of the word is concerned. For since words are signs of intellectual conceptions, we first give names to those things which we first understand, even though they may be subsequent in the order of nature. Now of all acts which are perceived by us in a sensible way, motion is the best known and most evident to us; and therefore the word actuality was first referred to motion, and from motion the word was extended to other things.

             1806. And for this reason motion is not attributed to non-existent things, although certain of the other categories mentioned above are attributed to nonexistents; for we say that non-existent things are intelligible, or thinkable, or even desirable, but we do not say that they are moved. For, since to be moved means to be actual, it follows that things which do not exist actually would exist actually; but this is obviously false. For even if some nonexistent things are potential, they are still not said to be, since they are not actual.

             1807. Now if what (759).

             Having destroyed the opinion of those who claim that nothing is possible except when it is actual, the Philosopher now destroys the opposite opinion of those who claim that all things are possible; and in regard to this he does two things. First, he destroys this opinion. Second (760:C 1810), he establishes a truth about the succession of possible things ("And at the same").

             He accordingly says, first (759), that, if it is true that a thing is said to be possible because something follows from it, inasmuch as the possible has been defined as that from which nothing impossible follows if it is assumed to exist, it is evident that the statements of some thinkers that anything is possible even if it never will be, cannot be true, since as a result of this position impossible things will be eliminated. For example, if one were to say that the diagonal of a square can be commensurate with a side, even though it is not commensurate with it (and one might speak in the same way about other impossible things), and not think that it is impossible for the diameter of a square to be commensurate with a side, those who maintain this position, I say, speak truly in one sense and in another they do not.

             1808. For there are some things which nothing will prevent us from designating as capable or possible of coming to be, even though they never will be or ever come to be; but this cannot be said of all things. Yet according to the doctrine laid down above, and which we are now to assume, only those things are capable of being or coming to be, even though they are not, from which nothing impossible follows when they are posited. However, when it is posited that the diagonal of a square is commensurate, an impossible conclusion follows. Thus it cannot be said that it is possible for the diagonal to be commensurate, for it is not only false but impossible.

             1809. Now some things are false only but not impossible, as that Socrates sits or that he stands. For to be false and to be impossible are not the same; for example, it is false that you are now standing, but it is not impossible. Therefore the foregoing opinion is true of some things, because some are possible even though they are false. However, it is not true of all things, because some are both false and impossible.

             1810. And at the same (760).

             And since he had said that a thing is judged possible because nothing impossible follows from it, he indicates the way in which there are possible consequents. He says that not only is the position in question destroyed by the definition of the possible given above, but it is also evident at the same time that, if the antecedent of a conditional proposition is possible, the consequent will also be possible; for example, if this conditional proposition, "If when A is, B is," is true, then if A is possible, B must be possible.

             1811. Now in order to understand this we must note that the word possible is used in two senses. It is used, first, in contradistinction to the necessary, as when we call those things possible which are capable either of being or not being. And when possible is taken in this way, the foregoing remarks do not apply. For nothing prevents the antecedent from being capable of being or not being, even though the consequent is necessary, as is clear in this conditional proposition, "If Socrates laughs, he is a man."

             1812. The word possible is used in a second sense inasmuch as it is common both to those things which are necessary and to those which are capable of being or not being, according as the possible is distinguished from the impossible. And the Philosopher is speaking of the possible in this way here when he says that the consequent must be possible if the antecedent was possible.

             1813. For let it be assumed that this conditional proposition is true: If A is, then B is; and let it be assumed that the antecedent, A, is possible. Then it is necessary that B either be possible or not. Now if it is necessary, then the assumption follows. But if it is not necessary, nothing prevents the opposite from being assumed, namely, that B is not possible. But this cannot stand; for A is assumed to be possible, and when it is assumed to be possible, it is at the same time assumed that nothing impossible follows from it; for the possible was defined above as that from which nothing impossible follows. But B follows from A, as was assumed, and B was assumed to be impossible; for to be impossible is the same as not to be possible. Therefore A will not be possible if B, which was held to be impossible, follows from it. Therefore let B be assumed to be impossible, and if it is impossible and, given A, B must exist, then both the first and the second, namely, A and B, will be impossible.

             1814. In which place it must be noted that the following proposition is correct: if the consequent is impossible, the antecedent is impossible; but the reverse is not true. For nothing prevents something necessary from being a consequence of the impossible, as in this conditional proposition, "If man is an ass, he is an animal." Therefore what the Philosopher says here must not be understood as meaning that, if the first, i.e., the antecedent, were impossible, then the second, i.e., the consequent, would also be impossible. But it must be understood to mean that, if the consequent is impossible, both will be impossible. Therefore it is obvious that, if A and B are so related that, when A is, B must be, it necessarily follows that, if A is possible, B will be possible; and if B is not possible when A is possible, then A and B are not related in the way supposed, namely, that B follows from A. But it is necessary that when A is possible B must be possible, if when A exists it is necessary that B exist. Therefore when I say "If A is, B is," this means that B must be possible if A is possible, in the sense that it is possible for B to exist at the same time and in the way in which A is possible; for it is not possible that it should exist at any time and in any way.