LESSON 6

Contradictories Cannot Be True at the Same Time

  Chapter 6: 1062b 20-1063b 35

             943. Now this difficulty may be solved by considering the origin of this view.

             944. For it seems to have arisen in some cases from the opinion of the philosophers of nature, and in others from the fact that not all men apprehend the same thing in the same way, but something appears pleasant to some and the opposite to others (352).

             945. For the view that nothing comes from non-being but everything from being is a doctrine common to nearly all those who have dealt with nature. Thus, since the not-white comes from what is actually white, and not from the not-white, should the not-white have come to be, what becomes not-white will have come to be from what is not not-white. Hence whiteness must come from nonbeing according to them, unless the white and the not-white are the same. But it is not hard to solve this difficulty; for we have stated in our physical treatises in what sense things which come to be come from non-being, and in what sense they come from being (355-356).

             946. But it is also foolish to occupy oneself equally with both opinions and with the fanciful statements of those who argue against themselves, because it is evident that one or the other of them must be wrong. This is clear from the facts of sensory perception; for the same thing never appears sweet to some and the opposite to others unless in some the organ of the sense which distinguishes the above-mentioned savors has been impaired or injured. And such being the case, some must be taken as the measure and the others not. And I say that the same thing applies in the case of good and evil, of beautiful and ugly, and of other attributes of this kind. For to maintain this view is not different from maintaining that what appears to those who push their finger under their eye and make one object appear to be two must therefore be two because it appears to be so many, and yet that it must be one because to those who do not move their eye the one object appears to be one (369-375).

             947. And in general seeing that things here are subject to change and never remain the same, it would be unfitting to base our judgment of the truth on this. For in pursuing the truth one must start with those things which are always the same and never undergo a single change. Such things are those which contain the world; for they do not appear at one time to be such and at another different, but they are always the same and admit of no change (365).

             948. Further, if there is motion, there is also something that is moved; and everything is moved from something and to something. Therefore that which is moved must be in that from which it is moved, and yet not be in it; and it must be moved to this and come to be in it; but contradictories cannot be true at the same time, as they claim.

             949. And if things here are in a state of continuous change and motion as regards quantity, and one were to suppose this even though it is not true, why should they not be permanent as regards quality? For the view that contradictories may be predicated of the same subject seems to be based largely on the assumption that the quantity of bodies does not remain constant; and for this reason they say that the same thing is and is not four cubits long. But a thing's substance involves quality, and this is of a determinate nature, whereas quantity is of an indeterminate nature (365).

             950. Further, when a physician orders them to take some particular food, why do they take it? For why is this particular food bread rather than not bread? Hence it would make no difference whether they ate it or not. But they take the food prescribed as though they know the truth about it and that it is the food prescribed. Yet they should not do this if there is no nature which remains fixed in the sensible world, but everything is always in a state of motion and flux (349).

             951. Again, if we are always undergoing change and never remain the same, what wonder is it if to us, as to those who are ill, things never appear the same? For to them also, since they are not in the same condition as when they were well, sensible qualities do not appear to be the same; yet sensible things themselves need not for this reason undergo any change, but they cause different, and not the same, impressions in those who are ill. And perhaps the same thing must happen to those who are well if the above-mentioned change takes place (950). However, if we do not change but always remain the same, there will be something permanent (357-359).

             952. Hence, in the case of those who raise the foregoing difficulties as a result of reasoning, it is not easy to meet their arguments unless they assume something and do not demand a reason for it; for every argument and demonstration comes about in this way. For those who admit nothing destroy discussion and reasoning in general, and thus there is no reasoning with such men. But in the case of those who are puzzled by the usual problems, it is easy to meet them and to reject the arguments which cause their difficulty. This becomes clear from what has been said above (943-951).

             953. It is evident from these considerations, then, that opposite statements cannot be verified of the same subject at one time (353; 376-377), nor can contrary ones, because every contrariety involves privation. This becomes clear if we reduce the definitions of all contraries to their principle (382). Similarly no intermediate can be predicated of one and the same subject. For if the subject is white, those who say that it is neither white nor black are wrong, for it then follows that it is white and is not white; for the second of the two terms which we have combined is true of it, and this is the contradictory of white (383-391).

             954. One cannot be right, then, in holding the views either of Heraclitus (940) or of Anaxagoras; and if this were not so it would follow that contraries would be predicated of the same subject. For when Anaxagoras says that there is a part of everything in everything else, he says that nothing is sweet any more than it is bitter, and so on with any of the other pairs of contraries, since everything is present in everything else, not potentially, but actually and separately.

             955. And similarly all statements cannot be true or all false, both because of many other difficulties which might be brought forward on the basis of this position, and because, if all statements are false, anyone who says this will not speak the truth; and if all are true, it will not be false to say that all are false (392).

COMMENTARY

             2225. Having argued against those who claim that contradictories may be verified of the same subject at the same time, the Philosopher now shows how these men can be persuaded to abandon this theory. His discussion is divided into two parts. In the first (943:C 2225) he explains his thesis. In the second (953:C 2243) he draws a corollary from what has been said ("It is evident").

             The first part is divided into two members. In the first he explains how it is possible in some cases to deal with the above-mentioned theory. In the second (952:C 2241) he indicates in what cases it can be refuted and in what not ("Hence, in the case").

             In treating the first (943) he does three things. First, he describes the way in which the foregoing theory can be disqualified in some cases. He says that the above-mentioned difficulty which led some people to adopt the position that contradictories may be verified of the same subject at the same time can be dispelled if one considers its source.

             2226. For it seems (944).

             Second, he gives two sources of this position. He says that this position seems to have arisen in some cases from the opinion of the philosophers of nature, who claimed that nothing comes to be from non-being, and in others from the fact that not all men make the same judgments about the same things, but something appears pleasant to some and just the opposite to others. For if one were to believe that whatever appears is true, it would follow from this that opposites are true at the same time.

             2227. For the view (945).

             Third, he shows how the above-mentioned position might follow from the two sources just given; and he points out how it may be dealt with. First, he shows how it might follow from the opinion of the philosophers of nature; and second (946:C 2227), from the belief that every appearance is true ("But it is also foolish").

             He accordingly says, first (945), that the doctrine common to nearly all of the thinkers who have dealt with nature is that nothing comes to be from non-being, but everything from being. It is clear that something becomes not-white from what is actually white; but what is not-white does not come from what is not-white. Further, it is also evident that what is not-white comes from what is not not-white. Consequently, it is evident that what is not not-white becomes not-white, just as what is not-black becomes black. It is clear, then, that that from which the not-white comes to be is the white, and it is not not-white. This cannot be understood in the sense that the not-white is entirely non-being, because it would then seem to follow that something comes to be from non-being absolutely. For example, if we were to say that fire comes from what is not-fire, there would be the question how they think that that from which fire comes to be is entirely not-fire. For it would then seem to follow, according to them, that something comes to be from non-being. Hence they claimed that fire lay hidden in that from which fire comes to be, as is evident from the opinion of Anaxagoras, which is given in Book I of the Physics. Similarly, they believed that, if something comes to be not-white from what is not not-white, the not-white must have preexisted in that from which it comes to be, as has been explained. Thus it would follow, according to them, that that from which the not-white comes to be is both white and not-white at the same time, unless it is assumed that something comes to be from non-being.

             2228. But this difficulty is not hard to solve, as the Philosopher points out; for it has been explained in Book I of the Physics how a thing comes to be from being and how from nonbeing; for it has been stated that something comes to be from what is a nonbeing in act, though it is incidentally a being in act. But it comes to be properly from matter, which is in potency; for it is accidental to the process of making that the matter from which a thing comes to be should be the subject of form and of privation. Thus it is not necessary that that from which a thing comes to be should be at the same time both a being and a nonbeing in act, but that it should be of itself in potency both to being and to non-being, i.e., both to form and to privation.

             2229. But it is also foolish (946).

             Then he rejects the foregoing opinion inasmuch as it might be derived from the other source, i.e., from the view that every appearance is judged to be true. First, he rejects this source; and second (947:C 2232), its cause ("And in general").

             He accordingly says, first (946), that, just as it is foolish to think that contradictories may be verified of the same subject at the same time, so too "it is also foolish to occupy oneself with," i.e., to accept, both of the foregoing opinions of the philosophers who argue against themselves; for it is obvious that one or the other of them must be in error.

             2230. This is evident from the facts of sensory perception; for the same thing never appears sweet to some and bitter to others, unless in some the sense organ and the power which discriminates between savors has been impaired or injured. But since this does happen in some cases, "some must be taken as the measure," i.e., the judgment of those whose senses are not impaired in this way must be taken as the rule and measure of truth. But this should not be understood to apply to those whose senses are impaired.

             2231. And what is evident in the case of sensory perception must also be said to apply in the case of good and evil, of beautiful and ugly, and of all attributes of this kind which are apprehended by the intellect. For if some conceive a thing to be good and others evil, the judgment of those whose intellect has not been impaired by some bad habit or by some bad influence or by some other cause of this kind must be the norm. For if someone were to hold that it is not less fitting to believe the one group rather than the other, this would not differ in any way from saying that things are as they appear "to those who push their finger under their eye," i.e., who move their eye with their finger, and thereby make one thing appear as two, and say that it must be two because it appears to be so many, and again that it must be one because it appears to be one to those who do not move their eye with their finger. For it is obvious that we must base our judgment about the oneness of things on the judgment which the eye makes when it does not receive some strange impression, and not on the judgment which it makes when it receives such an impression. Now a man judges one visible object to be two because the form of the visible object is made to appear as two to the organ of vision when it is moved; and this double impression reaches the organ of the common sense as though there were two visible objects.

             2232. And in general (947).

             Then he rejects the basis of the position that every appearance is true. For some held this because they thought that all things are in a state of continuous flux, and that there is nothing fixed and determinate in reality; and thus it would follow that a thing is such only when it is seen.

             2233. He therefore presents five arguments against this position. He says, first, that it is altogether unfitting to base our judgment about the whole truth on the fact that these sensible things which are near or close to us are undergoing change and are never permanent. But the truth must be based rather on those things which are always the same and never undergo any change as regards their substance, though they do appear to be subject to local motion. For such things are those "which contain the world," i.e., the celestial bodies, to which these corruptible bodies are compared as things that have no quantity, as the mathematicians prove. Now the celestial bodies are always the same and do not at one time appear to be such and at another different, for they admit of no change which affects their substance.

             2234. Further, if there (948).

             Then he gives the second argument against this position. The argument runs thus: if there is motion in these lower bodies, there must be something that is moved, and it must also be moved from something and to something. Hence that which is moved must already be in that from which it is moved and yet not be in it, and this must be moved to something else and be continuously coming to be in it. Thus some definite affirmation, as well as some negation, must be true. And it will not be necessary that a contradiction be true of the same subject, because according to this nothing would be moved. For if the same thing might be at the extreme to which it is moved and not be at it, there would be no reason why a thing which has not yet reached an extreme should be moved thereto, because it would already be there.

             2235. And if things (949).

             He gives the third argument; and with a view to making this clear it should be borne in mind that, when Heraclitus saw that a thing increased in size according to some definite and very small quantity over a long period of time (for example, a year), he thought that some addition would be made in any part of that time, and that it would be imperceptible because of the very small quantity involved. And because of this he was led to believe that all things, even those which seem to be static, are also being moved continuously by an imperceptible motion, and that after a long time their motion would become apparent to the senses. But his opinion about increase is false; for increase does not take place continuously in such a way that something grows in any part of time, but a body is disposed to increase during some time and then grows, as Aristotle makes quite clear in Book VIII of the Physics.

             2236. Hence he says that, if the bodies around us here are in a continuous state of flux and motion as regards quantity, and one wishes to admit this even though it is not true, there is no reason why a thing cannot be unchanging as to its quality. For the opinion that contradictories are true of the same subject at the same time seems to be based largely on the assumption that the quantitative aspect of bodies does not remain constant; and thus some thought that the same thing is and is not four cubits long. But a thing's substance is defined in terms of some quality, i.e., some form; and quality is of a determinate nature in things, although quantity is of an indeterminate nature because of change, as has been pointed out.

             2237. Further, when a physician (950).

             Then he gives the fourth argument, which runs thus: if there is nothing fixed in the world as regards being or non-being, why do they take this kind of bread which the physician prescribes and not that? For according to the position given above, why is this bread rather than not-bread? He implies that the answer cannot be in the affirmative any more than in the negative. And thus it would make no difference whether one ate the bread or did not. But we see that they take the bread which the physician prescribes, implying that they form a true judgment about bread itself, and that this kind of bread is really the one which the physician prescribes. Yet this would not be the case if no nature remained fixed in the sensible world but all things are always in a state of motion and flux.

             2238. Again, if we (951).

             Then he presents the fifth argument: since the above-mentioned position assumes that there is no fixed truth in things because of the continuous change which they undergo, if the truth is identical with appearance it is necessary to say that we men, who make judgments about other things, are either in motion or are not.

             2239. For if we are always undergoing change and never remain the same, it is not surprising that things never appear the same to us; and this is the case with those who are ill. For since they have been changed and are not in the same state as when they were well, the sensible qualities which they perceive by way of the senses will not seem the same to them as they did before they became ill. For to those whose sense of taste has been impaired sweet things seem bitter or tasteless; and the same is true of other sensible qualities. Yet sensible qualities themselves are not changed for this reason, but they cause different impressions in those who are ill because their senses are differently disposed. Therefore, if we men, who are continuously undergoing change, make different judgments about other things, this should not be attributed to things but to us.

             2240. However, if we are not changing but always remain the same, there will therefore be something permanent in the world and consequently some fixed truth about which we can make positive judgments. For we make judgments not only about other things but also about human nature.

             2241. Hence, in the case (952).

             Then he indicates who can be disabused of the above opinion and who can not. He says that, if those who adopt the foregoing opinions do so not because of any reasoning, in the sense that they do not assume anything because they are obstinate, and do not inquire into the reasons for the things that they say but stubbornly adhere to the opinions which they hold, it is not easy for them to give up an opinion of this kind. For every argument and every demonstration comes about in this way, namely, by admitting the truth of some statement and investigating the reason for it. But those who admit nothing destroy discussion and every rational argument; and thus no appeal of reason can be addressed to them whereby they can be dislodged from their error.

             2242. But if there are any who are perplexed because of certain deficiencies (for example, because they do not understand some things well), it is easy to dispel such an error by removing the difficulties which puzzle them. This is evident from the previous discussion in which he deals with the difficulties that could lead to the above-mentioned opinion.

             2243. It is evident (953).

             Then he draws three corollaries from what has been said. First, it is evident from the foregoing discussion that opposite statements cannot be verified of the same subject at one and the same time. Consequently it is clear from this that contraries cannot be verified of the same subject at the same time. And this is true because every contrariety involves privation; for one of two contraries is always a privation. This becomes evident if one wishes to reduce the definitions of contraries to their first principle; for contained in the notion of black is the privation of white. Since a privation, then, is a kind of negation having a determinate subject, it is evident that, if contraries were true of the same subject, both an affirmation and a negation would have to be true of the same subject at the same time.

             2244. Now it is not only impossible for two contraries to be true of the same subject at the same time, but it is also impossible for an intermediate to be predicated of one and the same subject of which one of two extremes is predicated; for from what has been said in Book X (880-86:C 2101-11) it is evident that an intermediate between contraries involves the privation of both extremes, whether it is designated by one word or by many or is nameless. Hence an intermediate between white and black, such as red or yellow, contains in its definition the fact that it is neither white nor black. Therefore, if one says that some subject is red when it is really white, he is saying at the same time that it is neither white nor black. Hence he is in error; for it would follow that that subject is both white and not white at the same time; because if it is true that that subject is neither white nor black, the other part of the copulative proposition may be verified of the same subject, and this is the contradictory of being white. Thus it follows that, if an intermediate and an extreme are true of the same subject, contradictories must be true of the same subject.

             2245. One cannot (954).

             He gives the second corollary. He concludes that, if an affirmation and a negation are not true at the same time, neither the opinion of Heraclitus nor that of Anaxagoras is true. That this is so regarding the opinion of Heraclitus is evident from what has been said. Hence he shows that the same thing applies with respect to the opinion of Anaxagoras. He says that, if Anaxagoras' opinion is not false, it follows that contraries may be predicated of the same subject, and therefore that contradictories may also be predicated of the same subject. This is shown as follows. Anaxagoras claimed that anything at all comes to be from anything at all, and everything which comes to be comes from something. Hence he was not compelled to maintain that something comes to be from nothing, and thus he claimed that everything is present in everything else. Therefore, since he posited that there is a part of everything in everything else (for example, a part of flesh in bone, and a part of whiteness in blackness, and vice versa), it follows that the whole is no more sweet than bitter. The same holds true of other contrarieties. And this is so if a part of anything is present in any whole not only potentially but actually and separately. And he added this because whatever comes to be from something else must pre-exist in it potentially and not actually. Hence contraries must preexist in the same subject potentially and not actually. This does not mean that contraries exist separately in something, because the potency for contraries is the same. But Anaxagoras did not know how to distinguish between potency and actuality.

             2246. And similarly (955).

             He gives the third corollary. He concludes from what has been said that both opinions are false, i.e., the opinion of those who said that all statements are true, and the opinion of those who said that all are false. This is evident because of the many difficult and serious conclusions which result from these opinions which have been brought together here and above in Book IV (332-402:C 611-748); and especially "because if all statements are false," he who says that every statement is false makes a statement and thus does not speak the truth. And similarly if all statements are true, he who says that all are false will not say what is false but will speak the truth. And for this reason the position of one who claims that all statements are true is destroyed.