Aristotle · a new plain-English translation from the original language
1| The study of truth is in one way difficult, in another way easy. A sign of this is that no one is able to attain it adequately, and yet not everyone fails, [993b] but each person says something about nature, and while individually each contributes nothing or little to it, from all of them taken together a considerable magnitude results. So that if the matter stands as we put it in the proverb, "who could miss the door?" — in this respect the study would be easy; but to be able to grasp the whole while unable to grasp a part shows its difficulty. But perhaps, since the difficulty is of two kinds, its cause lies not in the facts but in us; for just as the eyes of bats are related to the light of day, so too is the intellect of our soul related to the things that are by nature most evident of all. And it is right to feel gratitude not only toward those whose opinions one might share, but also toward those who declared themselves more superficially, for these too contributed something: they trained our state of mind beforehand. For if Timotheus had not existed, we would not have much of our lyric poetry; and if Phrynis had not existed, Timotheus would not have existed. The same holds, in the same way, for those who have declared themselves about the truth:
2| from some of them we have received certain opinions, while others have become the cause of these people's existing. It is also correct that philosophy is called the knowledge of truth. For the end of theoretical knowledge is truth, while that of practical knowledge is action; for even when those engaged in practical matters examine how something stands, they consider not what is eternal but what is relative to something and to the present moment. And we do not know what is true apart from the cause. Now each thing possesses a given attribute most of all among the things to which, by virtue of it, that same attribute belongs synonymously in the others as well (for example, fire is hottest of all things, since it is also the cause of heat in the other things). So too the truest thing is that which is the cause, for the things that come after it, of their being true. Hence the principles of things that always are must always be the truest things (for they are not merely true at some time, nor is there some cause of their being for them, but they are the cause of being for the other things), so that as each thing stands in regard to being, so too it stands in regard to truth.
3| [994a] But surely it is clear that there is some principle, and that the causes of things are not infinite, either in a straight line or in kind. For it is not possible that one thing come from another as from matter and proceed to infinity (for example, flesh from earth, earth from air, air from fire, and this never coming to a stop), nor can that from which the origin of motion comes go on to infinity (for example, man being moved by air, air by the sun, the sun by Strife, and this having no limit). Likewise the that-for-the-sake-of-which cannot go on to infinity — walking for the sake of health, health for the sake of happiness, happiness for the sake of something else, and so on, always one thing for the sake of another. And it is the same with the essence. For among intermediates, where there is some last term and an earlier one, the earlier term must be the cause of what comes after it. For if we had to say which of the three is the cause, we would name the first; certainly not the last, for the last is the cause of nothing; but surely not the middle term either, for it is the cause of only one thing (and it makes no difference whether there is one intermediate or several, or whether they are infinite or finite).
4| But of things infinite in this way, and of the infinite as a whole, all the parts alike are intermediate, right up to the present one, so that if there is no first term, there is no cause at all. But surely neither can one proceed to infinity downward, given that the upward series has a starting point — so that from fire comes water, and from this earth, and thus always some other kind coming to be. For one thing comes to be from another in two ways — not in the sense in which one thing is said to come after another, as the Olympic games come after the Isthmian, but either as a man comes from a boy by change, or as air comes from water. Now in the sense in which we say a man comes to be from a boy, we mean it as what has come to be comes from what is coming to be, or what has been completed comes from what is being completed (for there is always something in between, just as coming-to-be lies between being and not-being, so too what is coming to be lies between what is and what is not; for the learner is one who is becoming a knower, and this is what is meant when we say that a knower comes to be from a learner). But in the other sense — as water comes from air — one of the two is destroyed. That is why the first pair does not revert back into each other,
5| [994b] nor does a boy come to be from a man (for what is coming to be does not come from the process of coming-to-be, but is what exists after that coming-to-be; thus, too, day comes from dawn, because it comes after dawn — which is why dawn does not come from day). But the other pair reverts. In both ways it is impossible to go on to infinity: for in the case of things that are intermediates there must be an end, while the others revert into each other, since the destruction of the one is the coming-to-be of the other. At the same time, it is also impossible for the first term, being eternal, to be destroyed; for since the process of coming-to-be is not infinite in the upward direction, the first thing whose destruction brought something else into being cannot be eternal. Further, that for the sake of which is an end, and such is that which is not for the sake of another thing, but for whose sake the other things exist, so that if there is to be some such last term, the series will not be infinite, while if there is nothing of this sort, there will be no that-for-the-sake-of-which at all. But those who posit an infinite series unwittingly do away with the nature of the good (and yet no one would undertake to do anything unless he expected to reach a limit). Nor, on that view, could there be intellect among the things that are; for whoever possesses intellect always acts for the sake of something, and this is a limit — for the end is a limit.
6| But surely the essence cannot be reduced to another, more expansive definition either: for the earlier definition is always more truly a definition, and the later one is not, and where the first does not hold, neither does what depends on it. Further, those who speak this way do away with knowing altogether, for it is not possible to know before one arrives at the indivisibles. And understanding is likewise impossible, for how can things that are infinite in this way be grasped in thought? It is not the same as with a line: a line does not come to a halt in respect of its divisions, yet it is not possible to think it without bringing the division to a halt (which is why someone traversing the infinite will not end up counting the cuts); rather, one is compelled to think the whole line without traversing it. And nothing infinite can have being; if it could, then being infinite would not, after all, be infinite. But further, even if the kinds of causes were infinite in number, knowing would still be impossible on that basis, for we think we know only when we have come to recognize the causes; and what is infinite by addition cannot be gone through within a finite span. Now our habits of listening are governed by custom: we require things to be said in the way we are accustomed to hearing them,
7| [995a] and whatever departs from this does not seem comparable but, because of its unfamiliarity, seems less knowable and more foreign; for what is customary is what is known. How much power custom has, the laws show, in which the mythical and childish elements carry more weight than our actual knowledge of them, simply through habituation. So some people will not accept what is said unless it is put mathematically, others unless it proceeds by examples, and others demand that a poet be brought in as a witness. Some want everything treated with exactness, while others are put off by exactness, either because they cannot follow a connected chain of reasoning or because they find it petty; for exactness has something about it such that, just as in business dealings, so too in arguments, it strikes some people as ungenerous. Hence one must be trained in how each subject is to be received, since it is absurd to pursue both a science and the proper manner of that science at the same time, and neither of the two is easy to grasp on its own. Mathematical exactness should not be demanded in every case, but only in things that have no matter. That is why this is not the manner proper to natural science, since presumably all of nature involves matter. Hence one must first examine what nature is, for in this way it will also become clear what the subjects of natural science are, and whether it belongs to one science or to several to study the causes and the principles.