Chapter 1 edit
The investigation of the truth is in one way hard, in another easy. An indication of this is found in the fact that no one is able to attain the truth adequately, while, on the other hand, no one fails entirely, but every one says something true about the nature of things, and while individually they contribute little or nothing to the truth, by the union of all a considerable amount is amassed. Therefore, since the truth seems to be like the proverbial door, which no one can fail to hit, in this way it is easy, but the fact that we can have a whole truth and not the particular part we aim at shows the difficulty of it.
Perhaps, as difficulties are of two kinds, the cause of the present difficulty is not in the facts but in us. For as the eyes of bats are to the blaze of day, so is the reason in our soul to the things which are by nature most evident of all.
It is just that we should be grateful, not only to those whose opinions we may share, but also to those who have expressed more superficial views; for these also contributed something, by developing before us the powers of thought. It is true that if there had been no Timotheus we should have been without much of our lyric poetry; but if there had been no Phrynis there would have been no Timotheus. The same holds good of those who have expressed views about the truth; for from the better thinkers we have inherited certain opinions, while the others have been responsible for the appearance of the better thinkers.
It is right also that philosophy should be called knowledge of the truth. For the end of theoretical knowledge is truth, while that of practical knowledge is action (for even if they consider how things are, practical men do not study the cause in itself, but in some relation and at some time). Now we do not know a truth without its cause; and a thing has a quality in a higher degree than other things if in virtue of it the similar quality belongs to the other things (e. g. fire is the hottest of things; for it is the cause of the heat of all other things); so that that which causes derivative truths to be true is most true. Therefore the principles of eternal things must be always most true; for they are not merely sometimes true, nor is there any cause of their being, but they themselves are the cause of the being of other things, so that as each thing is in respect of being, so is it in respect of truth.
Chapter 2 edit
Evidently there is a first principle, and the causes of things are neither an infinite series nor infinitely various in kind. For (1), on the one hand, one thing cannot proceed from another, as from matter, ad infinitum, e. g. flesh from earth, earth from air, air from fire, and so on without stopping; nor on the other hand can the efficient causes form an endless series, man for instance being acted on by air, air by the sun, the sun by Strife, and so on without limit. Similarly the final causes cannot go on ad infinitum,—walking for the sake of health, this for the sake of happiness, happiness for the sake of something else, and so one thing always for the sake of another. And the case of the formal cause is similar. For in the case of an intermediate, which has a last term and a prior term outside it, the prior must be the cause of the later terms. For if we had to say which of the three is the cause, we should say the first; surely not the last, for the final term is the cause of none; nor even the intermediate, for it is the cause only of one. It makes no difference whether there is one intermediate or more, nor whether they are infinite or finite in number. But of series which are infinite in this way, and of the infinite in general, all the parts down to that now present are alike intermediates; so that if there is no first there is no cause at all.
Nor can there be an infinite process downwards, with a beginning in the upper direction, so that water should proceed from fire, earth from water, and so always some other kind should be produced. For one thing comes from another in two ways (if we exclude the sense in which 'from' means 'after' as we say 'from the Isthmian games come the Olympian'), (a) as the man comes from the boy, by the boy's changing, or (b) as air comes from water. By 'as the man comes from the boy' we mean 'as that which has come to be from that which is coming to be, or as that which is finished from that which is being achieved' (for as becoming is between being and not being, so that which is becoming is always between that which is and that which is not; and the learner is a man of science in the making, and this is what is meant when we say that from a learner a man of science is being made); on the other hand, coming from another thing as water comes from air implies the destruction of the other thing. This is why changes of the former kind are not reversible,—the boy does not come from the man (for that which comes to be does not come to be from the process of coming to be, but exists after[1] the process of coming to be; for it is thus that the day comes from the morning—in the sense that it comes after the morning; and therefore the morning cannot come from the day); but changes of the other kind are reversible. But in both cases it is impossible that the number of terms should be infinite. For terms of the former kind being intermediates[2] must have an end, and terms of the latter kind change into one another; for the destruction of either is the generation of the other.
At the same time it is impossible that the first cause, being eternal, should be destroyed; for while the process of becoming is not infinite in the upward direction, a first cause by whose destruction something came to be could not be eternal.[3]
Further, the final cause is an end, and that sort of end which is not for the sake of something ebe, but for whose sake everything else is; so that if there is to be a last term of this sort, the process will not be infinite; but if there is no such term there will be no final cause. But those who maintain the infinite series destroy the Good without knowing it. Yet no one would try to do anything if he were not going to come to a limit. Nor would there be reason in the world; the reasonable man, at least, always acts for a purpose; and this is a limit, for the end is a limit.
But the formal cause, also, cannot be reduced always to another definition which is fuller in expression.[4] For the original definition is always more of a definition, and not the later one; and in a series in which the first term is not correct, the next is not so either.—Further, those who speak thus destroy science; for it is not possible to have this till one comes to the indivisible concepts. And knowledge becomes impossible; for how can one think things that are infinite in this way[5]? For this is not like the case of the line, to whose divisibility there is no stop, but which we cannot think if we do not make a stop; so that one who is tracing the infinitely divisible line cannot be counting the possibilities of section.
But further, the matter in a changeable thing must be cognized[6].
Again, nothing infinite can exist; and if it could, at least being infinite is not infinite.[7]
But (2) if the kinds of causes had been infinite in number, then also knowledge would have been impossible; for we think we know, only when we have ascertained all the causes, but that which is infinite by addition cannot be gone through in a finite time.
Chapter 3 edit
The effect which lectures produce on a hearer depends on his habits; for we demand the language we are accustomed to, and that which is different from this seems not in keeping but somewhat unintelligible and foreign because of its unwontedness. For the customary is more intelligible. The force of habit is shown by the laws, in whose case, with regard to the legendary and childish elements in them, habit has more influence than our knowledge about them. Some people do not listen to a speaker unless he speaks mathematically, others unless he gives instances, while others expect him to cite a poet as witness. And some want to have everything done accurately, while others are annoyed by accuracy, either because they cannot follow the connexion of thought or because they regard it as pettifoggery. For accuracy has something of this character, so that as in trade so in argument some people think it mean. Therefore one must be already trained to know how to take each sort of argument, since it is absurd to seek at the same time knowledge and the way of attaining knowledge; and neither is easy to get.
The minute accuracy of mathematics is not to be demanded in all cases, but only in the case of things which have no matter. Therefore its method is not that of natural science; for presumably all nature has matter. Hence we must inquire first what nature is: for thus we shall also see what natural science treats of [and whether it belongs to one science or to more to investigate the causes and the principles of things].[8]
- ↑ 994b1 The meaning seems to be, that in this kind of change the y that comes from x is not simply x rearranged, but x affected by a lapse of time. ∴ x cannot be got from y.
- ↑ Cf. a27-29.
- ↑ This paragraph is very obscure. Aristotle has in a11-19 given a general argument which applies to all the four causes, to show that there must always be a first cause. This, he assumes, must be eternal. He now applies this argument to the prime material cause, and shows that it must be indestructible. There are two difficulties in the paragraph:—
(1) It seems pointless to say that the first cause must be indestructible because it is eternal. Ground and consequent appear to be identical. But probably the object is to show that the first cause must be to its effects not as water to air but as boy to man. It develops into them, and is not destroyed when they come into being.
(2) The clause beginning with ἐπεί seems, as is often the case, to be elliptical. The meaning probably is:—'Since the process of becoming is not infinite in the upward direction, <there must be an eternal first cause, but> a first cause by whose destruction something came to be could not be eternal.' - ↑ i. e. one can reduce the definition of man as 'mortal rational animal' to 'mortal rational sensitive living substance', but one cannot carry on process ad infinitum.
- ↑ i. e. actually infinite.
- ↑ Sc. and therefore cannot form an infinite series.
- ↑ i. e. the notion of infinity does not contain an infinite number of marks.
- ↑ This clause has probably been wrongly inserted from 995b6.