But to attend equally to the opinions and the fancies of disputing parties is childish; for clearly one of them must be mistaken. (35) And this is evident from what happens in respect of sensation; for the same thing never appears sweet to some and the contrary of sweet to others, unless in the one case the sense-organ which discriminates the aforesaid flavours has been perverted and injured. [1063a] And if this is so the one party must be taken to be the measure, and the other must not. (5) And I say the same of good and bad, and beautiful and ugly, and all other such qualities. For to maintain the view we are opposing is just like maintaining that the things that appear to people who put their finger under their eye and make the object appear two instead of one must be two (because they appear to be of that number) and again one (for to those who do not interfere with their eye the one object appears one).34
In general, (10) it is absurd to make the fact that the things of this earth are observed to change and never to remain in the same state, the basis of our judgment about the truth. For in pursuing the truth one must start from the things that are always in the same state and suffer no change. Such are the heavenly bodies; for these do not appear to be now of one nature and again of another, (15) but are manifestly always the same and share in no change.35
Further, if there is movement, there is also something moved, and everything is moved out of something and into something; it follows that that which is moved must first be in that out of which it is to be moved, and then not be in it, and move into the other and come to be in it, (20) and that the contradictory statements are not true at the same time, as these thinkers assert they are.
And if the things of this earth continuously flow and move in respect of quantity—if one were to suppose this, although it is not true—why should they not endure in respect of quality? For the assertion of contradictory statements about the same thing seems to have arisen largely from the belief that the quantity of bodies does not endure, (25) which, our opponents hold, justifies them in saying that the same thing both is and is not four cubits long. But essence depends on quality, and this is of determinate nature, though quantity is of indeterminate.36
Further, when the doctor orders people to take some particular food, why do they take it? In what respect is ‘this is bread’ truer than ‘this is not bread’? And so it would make no difference whether one ate or not. (30) But as a matter of fact they take the food which is ordered, assuming that they know the truth about it and that it is bread. Yet they should not, if there were no fixed constant nature in sensible things, but all natures moved and flowed for ever.37
Again, if we are always changing and never remain the same, (35) what wonder is it if to us, as to the sick, things never appear the same? (For to them also, because they are not in the same condition as when they were well, sensible qualities do not appear alike; yet, for all that, the sensible things themselves need not share in any change, though they produce different, and not identical, sensations in the sick. [1063b] And the same must surely happen to the healthy if the aforesaid38 change takes place. (5)) But if we do not change but remain the same, there will be something that endures.39
As for those to whom the difficulties mentioned are suggested by reasoning, it is not easy to solve the difficulties to their satisfaction, unless they will posit something and no longer demand a reason for it; for it is only thus that all reasoning and all proof is accomplished; if they posit nothing, (10) they destroy discussion and all reasoning. Therefore with such men there is no reasoning. But as for those who are perplexed by the traditional difficulties, it is easy to meet them and to dissipate the causes of their perplexity. This is evident from what has been said.40
It is manifest, (15) therefore, from these arguments that contradictory statements cannot be truly made about the same subject at one time,41 nor can contrary statements, because every contrariety depends on privation. This is evident if we reduce the definitions of contraries to their principle.42
Similarly, no intermediate between contraries can be predicated of one and the same subject, of which one of the contraries is predicated. (20) If the subject is white we shall be wrong in saying it is neither black nor white, for then it follows that it is and is not white; for the second of the two terms we have put together43 is true of it, and this is the contradictory of white.44
We could not be right, then, in accepting the views either of Heraclitus45 or of Anaxagoras. (25) If we were, it would follow that contraries would be predicated of the same subject; for when Anaxagoras says that in everything there is a part of everything, he says nothing is sweet any more than it is bitter, and so with any other pair of contraries, since in everything everything is present not potentially only, (30) but actually and separately. And similarly all statements cannot be false nor all true, both because of many other difficulties which might be adduced as arising from this position, and because if all are false it will not be true to say even this, and if all are true it will not be false to say all are false.46 (35)
7 [1064a] Every science seeks certain principles and causes for each of its objects—e. g. medicine and gymnastics and each of the other sciences, whether productive or mathematical. For each of these marks off a certain class of things for itself and busies itself about this as about something existing and real—not however qua real; the science that does this is another distinct from these. (5) Of the sciences mentioned each gets somehow the ‘what’ in some class of things and tries to prove the other truths, with more or less precision. Some get the ‘what’ through perception, others by hypothesis; so that it is clear from an induction of this sort that there is no demonstration of the substance or ‘what’.
There is a science of nature, and evidently it must be different both from practical and from productive science. (10) For in the case of productive science the principle of movement is in the producer and not in the product, and is either an art or some other faculty. And similarly in practical science the movement is not in the thing done, but rather in the doers. But the science of the natural philosopher deals with the things that have in themselves a principle of movement. (15) It is clear from these facts, then, that natural science must be neither practical nor productive, but theoretical (for it must fall into some one of these classes). And since each of the sciences must somehow know the ‘what’ and use this as a principle, we must not fail to observe how the natural philosopher should define things and how he should state the definition of the essence—whether as akin to ‘snub’ or rather to ‘concave’. (20) For of these the definition of ‘snub’ includes the matter of the thing, but that of ‘concave’ is independent of the matter; for snubness is found in a nose, (25) so that we look for its definition without eliminating the nose, for what is snub is a concave nose. Evidently then the definition of flesh also and of the eye and of the other parts must always be stated without eliminating the matter.
Since there is a science of being qua being and capable of existing apart, we must consider whether this is to be regarded as the same as physics or rather as different. Physics deals with the things that have a principle of movement in themselves; mathematics is theoretical, (30) and is a science that deals with things that are at rest, but its subjects cannot exist apart. Therefore about that which can exist apart and is unmovable there is a science different from both of these, if there is a substance of this nature (I mean separable and unmovable), (35) as we shall try to prove there is.47 And if there is such a kind of thing in the world, here must surely be the divine, and this must be the first and most dominant principle. [1064b] Evidently, then, there are three kinds of theoretical sciences—physics, mathematics, theology. The class of theoretical sciences is the best, and of these themselves the last named is best; for it deals with the highest of existing things, (5) and each science is called better or worse in virtue of its proper object.
One might raise the question whether the science of being qua being is to be regarded as universal or not. Each of the mathematical sciences deals
with some one determinate class of things, but universal mathematics applies alike to all. Now if natural substances are the first of existing things, (10) physics must be the first of sciences; but if there is another entity and substance, separable and unmovable, the knowledge of it must be different and prior to physics and universal because it is prior.48
8 Since ‘being’ in general has several senses, (15) of which one is ‘being by accident’, we must consider first that which ‘is’ in this sense. Evidently none of the traditional sciences busies itself about the accidental. For neither does architecture consider what will happen to those who are to use the house (e. g. whether they will have a painful life in it or not), (20) nor does weaving, or shoemaking, or the confectioner’s art, do the like; but each of these sciences considers only what is peculiar to it, i. e. its proper end. And as for the argument that ‘when he who is musical becomes lettered he will be both at once, (25) not having been both before; and that which is, not always having been, must have come to be; therefore he must have at once become musical and lettered’—this none of the recognized sciences considers, but only sophistic; for this alone busies itself about the accidental, so that Plato is not far wrong when he says49 that the sophist spends his time on non-being.
That a science of the accidental is not even possible will be evident if we try to see what the accidental really is. (30) We say that everything either is always and of necessity (necessity not in the sense of violence, (35) but that which we appeal to in demonstrations), or is for the most part, or is neither for the most part, nor always and of necessity, but merely as it chances; e. g. there might be cold in the dog-days, but this occurs neither always and of necessity, nor for the most part, though it might happen sometimes. [1065a] The accidental, then, is what occurs, but not always nor of necessity, nor for the most part. Now we have said what the accidental is, and it is obvious why there is no science of such a thing; for all science is of that which is always or for the most part, (5) but the accidental is in neither of these classes.
Evidently there are not causes and principles of the accidental, of the same kind as there are of the essential; for if there were, everything would be of necessity. If A is when B is, and B is when C is, and if C exists not by chance but of necessity, (10) that also of which C was cause will exist of necessity, down to the last causatum as it is called (but this was supposed to be accidental). Therefore all things will be of necessity, and chance and the possibility of a thing’s either occurring or not occurring are removed entirely from the range of events. And if the cause be supposed not to exist but to be coming to be, the same results will follow; everything will occur of necessity. For to-morrow’s eclipse will occur if A occurs, (15) and A if B occurs, and B if C occurs; and in this way if we subtract time from the limited time between now and to-morrow we shall come sometime to the already existing condition. Therefore since this exists, everything after this will occur of necessity, (20) so that all things occur of necessity.
As to that which ‘is’ in the sense of being true or of being by accident, the former depends on a combination in thought and is an affection of thought (which is the reason why it is the principles, not of that which ‘is’ in this sense, but of that which is outside and can exist apart, that are sought); and the latter is not necessary but indeterminate (I mean the accidental) ; and of such a thing the causes are unordered and indefinite.50 (25)
Adaptation to an end is found in events that happen by nature or as the result of thought. It is ‘luck’ when one of these events51 happens by accident. For as a thing may exist, so it may be a cause, either by its own nature or by accident.52 Luck is an accidental cause at work in such events adapted to an end as are usually effected in accordance with purpose. (30) And so luck and thought are concerned with the same sphere; for purpose cannot exist without thought. The causes from which lucky results might happen are indeterminate; (35) and so luck is obscure to human calculation and is a cause by accident, but in the unqualified sense a cause of nothing.53 It is good or bad luck when the result is good or evil; and prosperity or misfortune when the scale of the results is large. [1065b]54
Since nothing accidental is prior to the essential, neither are accidental causes prior. If, then, luck or spontaneity is a cause of the material universe, reason and nature are causes before it.55
9 Some things are only actually, some potentially, (5) some potentially and actually, what they are, viz. in one case a particular reality, in another, characterized by a particular quantity, or the like.56 There is no movement apart from things; for change is always according to the categories of being, and there is nothing common to these and in no one category. But each of the categories belongs to all its subjects in either of two ways (e. g. ‘this-ness’—for one kind of it is ‘positive form’, (10) and the other is ‘privation’; and as regards quality one kind is ‘white’ and the other ‘black’, and as regards quantity one kind is ‘complete’ and the other ‘incomplete’, and as regards spatial movement one is ‘upwards’ and the other ‘downwards’, or one thing is ‘light’ and another ‘heavy’); so that there are as many kinds of movement and change as of being. (15) There being a distinction in each class of things between the potential and the completely real, I call the actuality of the potential as such, movement. That what we say is true, is plain from the following facts. When the ‘buildable’, in so far as it is what we mean by ‘buildable’,57 exists actually, it is being built, and this is the process of building. Similarly with learning, healing, walking, (20) leaping, ageing, ripening.58 Movement takes place when the complete reality itself exists, and neither earlier nor later.59 The complete reality, then, of that which exists potentially, when it is completely real and actual, not qua itself, but qua movable, is movement. By qua I mean this: bronze is potentially a statue; but yet it is not the complete reality of bronze qua bronze that is movement. (25) For it is not the same thing to be bronze and to be a certain potency. If it were absolutely the same in its definition, the complete reality of bronze would have been a movement. But it is not the same. (This is evident in the case of contraries; for to be capable of being well and to be capable of being ill are not the same—for if they were, being well and being ill would have been the same—it is that which underlies and is healthy or diseased, (30) whether it is moisture or blood, that is one and the same.) And since it is not the same, as colour and the visible are not the same, it is the complete reality of the potential, and as potential, (35) that is movement. That it is this, and that movement takes place when the complete reality itself exists, and neither earlier nor later, is evident. [1066a] For each thing is capable of being sometimes actual, sometimes not, e. g. the buildable qua buildable; and the actuality of the buildable qua buildable is building. For the actuality is either this—the act of building—or the house. But when the house exists, it is no longer buildable; the buildable is what is being built. (5) The actuality, then, must be the act of building, and this is a movement. And the same account applies to all other movements.
That what we have said is right is evident from what all others say about movement, and from the fact that it is not easy to define it otherwise. For firstly one cannot put it in any other class. (10) This is evident from what people say. Some call it otherness and inequality and the unreal;60 none of these, however, is necessarily moved, and further, change is not either to these or from these any more than from their opposites. The reason why people put movement in these classes is that it is thought to be something indefinite, and the principles in one of the two ‘columns of contraries’ are indefinite because they are privative, (15) for none of them is either a ‘this’ or a ‘such’ or in any of the other categories. And the reason why movement is thought to be indefinite is that it cannot be classed either with the potency of things or with their actuality; for neither that which is capable of being of a certain quantity, nor that which is actually of a certain quantity, is of necessity moved, and movement is thought to be an actuality, (
20) but incomplete; the reason is that the potential, whose actuality it is, is incomplete. And therefore it is hard to grasp what movement is; for it must be classed either under privation or under potency or under absolute actuality, but evidently none of these is possible. Therefore what remains is that it must be what we said—both actuality and the actuality we have described—which is hard to detect but capable of existing.61 (25)
And evidently movement is in the movable; for it is the complete realization of this by that which is capable of causing movement. And the actuality of that which is capable of causing movement is no other than that of the movable. For it must be the complete reality of both. For while a thing is capable of causing movement because it can do this, it is a mover because it is active; but it is on the movable that it is capable of acting, (30) so that the actuality of both is one, just as there is the same interval from one to two as from two to one, and as the steep ascent and the steep descent are one, but the being of them is not one; the case of the mover and the moved is similar.62
10 The infinite is either that which is incapable of being traversed because it is not its nature to be traversed (this corresponds to the sense in which the voice is ‘invisible’), (35) or that which admits only of incomplete traverse or scarcely admits of traverse, or that which, though it naturally admits of traverse, is not traversed or limited; further, a thing may be infinite in respect of addition or of subtraction, or both. The infinite cannot be a separate, independent thing. [1066b] For if it is neither a spatial magnitude nor a plurality, but infinity itself is its substance and not an accident of it, it will be indivisible; for the divisible is either magnitude or plurality. But if indivisible, it is not infinite, except as the voice is invisible; but people do not mean this, (5) nor are we examining this sort of infinite, but the infinite as untraversable.63 Further, how can an infinite exist by itself, unless number and magnitude also exist by themselves—since infinity is an attribute of these?64 Further, if the infinite is an accident of something else, (10) it cannot be qua infinite an element in things, as the invisible is not an element in speech, though the voice is invisible.65 And evidently the infinite cannot exist actually. For then any part of it that might be taken would be infinite (for ‘to be infinite’ and ‘the infinite’ are the same, if the infinite is substance and not predicated of a subject). Therefore it is either indivisible, or if it is partible, (15) it is divisible into infinites; but the same thing cannot be many infinites (as a part of air is air, so a part of the infinite would be infinite, if the infinite is a substance and a principle). Therefore it must be impartible and indivisible. But the actually infinite cannot be indivisible; for it must be of a certain quantity. Therefore infinity belongs to its subject incidentally. (20) But if so, then (as we have said66) it cannot be it that is a principle, but that of which it is an accident—the air or the even number.67
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