In what way the material circumstances are to be distinguished from those which are immaterial, or why some of the circumstances are material and others not so, we are not yet ready to point out. We must first observe, that there is a principle implied in the very statement of what Induction is; an assumption with regard to the course of nature and the order of the universe; namely, that there are such things in nature as parallel cases; that what happens once, will, under a sufficient degree of similarity of circumstances, happen again, and not only again, but as often as the same circumstances recur5. This, I say, is an assumption, involved in every case of induction. And, if we consult the actual course of nature, we find that the assumption is warranted. The universe, so far as known to us, is so constituted, that whatever is true in any one case, is true in all cases of a certain description; the only difficulty is, to find what description.
This universal fact, which is our warrant for all inferences from experience, has been described by different philosophers in different forms of language: that the course of nature is uniform; that the universe is governed by general laws; and [Pg 342]the like. One of the most usual of these modes of expression, but also one of the most inadequate6, is that which has been brought into familiar use by the metaphysicians of the school of Reid and Stewart. The disposition7 of the human mind to generalize from experience,—a propensity8 considered by these philosophers as an instinct of our nature,—they usually describe under some such name as "our intuitive conviction that the future will resemble the past." Now it has been well pointed9 out by Mr. Bailey,[8] that (whether the tendency be or not an original and ultimate element of our nature), Time, in its modifications10 of past, present, and future, has no concern either with the belief itself, or with the grounds of it. We believe that fire will burn to-morrow, because it burned to-day and yesterday; but we believe, on precisely11 the same grounds, that it burned before we were born, and that it burns this very day in Cochin-China. It is not from the past to the future, as past and future, that we infer, but from the known to the unknown; from facts observed to facts unobserved; from what we have perceived, or been directly conscious of, to what has not come within our experience. In this last predicament is the whole region of the future; but also the vastly greater portion of the present and of the past.
Whatever be the most proper mode of expressing it, the proposition that the course of nature is uniform, is the fundamental principle, or general axiom, of Induction. It would yet be a great error to offer this large generalization as any explanation of the inductive process. On the contrary, I hold it to be itself an instance of induction, and induction by no means of the most obvious kind. Far from being the first induction we make, it is one of the last, or at all events one of those which are latest in attaining12 strict philosophical13 accuracy. As a general maxim14, indeed, it has scarcely entered into the minds of any but philosophers; nor even by them, as we shall have many opportunities of remarking, have its extent and limits been always very justly conceived. The truth is, that this great generalization is itself founded on prior generalizations15. [Pg 343]The obscurer laws of nature were discovered by means of it, but the more obvious ones must have been understood and assented17 to as general truths before it was ever heard of. We should never have thought of affirming that all phenomena18 take place according to general laws, if we had not first arrived, in the case of a great multitude of phenomena, at some knowledge of the laws themselves; which could be done no otherwise than by induction. In what sense, then, can a principle, which is so far from being our earliest induction, be regarded as our warrant for all the others? In the only sense, in which (as we have already seen) the general propositions which we place at the head of our reasonings when we throw them into syllogisms, ever really contribute to their validity. As Archbishop Whately remarks, every induction is a syllogism19 with the major premise20 suppressed; or (as I prefer expressing it) every induction may be thrown into the form of a syllogism, by supplying a major premise. If this be actually done, the principle which we are now considering, that of the uniformity of the course of nature, will appear as the ultimate major premise of all inductions21, and will, therefore, stand to all inductions in the relation in which, as has been shown at so much length, the major proposition of a syllogism always stands to the conclusion; not contributing at all to prove it, but being a necessary condition of its being proved; since no conclusion is proved, for which there cannot be found a true major premise.[9]
The statement, that the uniformity of the course of nature is the ultimate major premise in all cases of induction, may be thought to require some explanation. The immediate22 major premise in every inductive argument, it certainly is not. Of that, Archbishop Whately's must be held to be the correct account. The induction, "John, Peter, &c. are mortal, therefore all mankind are mortal," may, as he justly says, be thrown into a syllogism by prefixing as a major premise (what is at any rate a necessary condition of the validity of the argument) namely, that what is true of John, Peter, &c. is true of all mankind. But how came we by this major premise? It is not self-evident; nay23, in all cases of unwarranted generalization, it is not true. How, then, is it arrived at? Necessarily either by induction or ratiocination24; and if by induction, the process, like all other inductive arguments, may be thrown into the form of a syllogism. This previous syllogism it is, therefore, necessary to construct. There is, in the long run, only one possible construction. The real proof that what is true of John, Peter, &c. is true of all mankind, can only be, that a different supposition would be inconsistent with the uniformity which we know to exist in the course of nature. [Pg 345]Whether there would be this inconsistency or not, may be a matter of long and delicate inquiry25; but unless there would, we have no sufficient ground for the major of the inductive syllogism. It hence appears, that if we throw the whole course of any inductive argument into a series of syllogisms, we shall arrive by more or fewer steps at an ultimate syllogism, which will have for its major premise the principle, or axiom, of the uniformity of the course of nature.[10]
It was not to be expected that in the case of this axiom, any more than of other axioms, there should be unanimity26 among thinkers with respect to the grounds on which it is to be received as true. I have already stated that I regard it as itself a generalization from experience. Others hold it to be a principle which, antecedently to any verification by experience, we are compelled by the constitution of our thinking faculty27 to assume as true. Having so recently, and at so much length, combated a similar doctrine28 as applied29 to the axioms of mathematics, by arguments which are in a great measure applicable to the present case, I shall defer30 the more particular discussion of this controverted31 point in regard to the fundamental axiom of induction, until a more advanced period of our inquiry.[11] [Pg 346]At present it is of more importance to understand thoroughly32 the import of the axiom itself. For the proposition, that the course of nature is uniform, possesses rather the brevity suitable to popular, than the precision requisite33 in philosophical language: its terms require to be explained, and a stricter than their ordinary signification given to them, before the truth of the assertion can be admitted.
§ 2. Every person's consciousness assures him that he does not always expect uniformity in the course of events; he does not always believe that the unknown will be similar to the known, that the future will resemble the past. Nobody believes that the succession of rain and fine weather will be the same in every future year as in the present. Nobody expects to have the same dreams repeated every night. On the contrary, everybody mentions it as something extraordinary, if the course of nature is constant, and resembles itself, in these particulars. To look for constancy where constancy is not to be expected, as for instance that a day which has once brought good fortune will always be a fortunate day, is justly accounted superstition34.
The course of nature, in truth, is not only uniform, it is also infinitely35 various. Some phenomena are always seen to recur in the very same combinations in which we met with them at first; others seem altogether capricious; while some, which we had been accustomed to regard as bound down exclusively to a particular set of combinations, we unexpectedly find detached from some of the elements with which we had hitherto found them conjoined, and united to others of quite a contrary description. To an inhabitant of Central Africa, fifty years ago, no fact probably appeared to rest on more uniform experience than this, that all human beings are black. To Europeans, not many years ago, the proposition, All swans are white, appeared an equally unequivocal instance of uniformity in the course of nature. Further experience has proved to both that they were mistaken; but they had to wait fifty centuries for this experience. During that long time, [Pg 347]mankind believed in an uniformity of the course of nature where no such uniformity really existed.
According to the notion which the ancients entertained of induction, the foregoing were cases of as legitimate36 inference as any inductions whatever. In these two instances, in which, the conclusion being false, the ground of inference must have been insufficient37, there was, nevertheless, as much ground for it as this conception of induction admitted of. The induction of the ancients has been well described by Bacon, under the name of "Inductio per enumerationem simplicem, ubi non reperitur instantia contradictoria." It consists in ascribing the character of general truths to all propositions which are true in every instance that we happen to know of. This is the kind of induction which is natural to the mind when unaccustomed to scientific methods. The tendency, which some call an instinct, and which others account for by association, to infer the future from the past, the known from the unknown, is simply a habit of expecting that what has been found true once or several times, and never yet found false, will be found true again. Whether the instances are few or many, conclusive39 or inconclusive, does not much affect the matter: these are considerations which occur only on reflection; the unprompted tendency of the mind is to generalize its experience, provided this points all in one direction; provided no other experience of a conflicting character comes unsought. The notion of seeking it, of experimenting for it, of interrogating40 nature (to use Bacon's expression) is of much later growth. The observation of nature, by uncultivated intellects, is purely41 passive: they accept the facts which present themselves, without taking the trouble of searching for more: it is a superior mind only which asks itself what facts are needed to enable it to come to a safe conclusion, and then looks out for these.
But though we have always a propensity to generalize from unvarying experience, we are not always warranted in doing so. Before we can be at liberty to conclude that something is universally true because we have never known an [Pg 348]instance to the contrary, we must have reason to believe that if there were in nature any instances to the contrary, we should have known of them. This assurance, in the great majority of cases, we cannot have, or can have only in a very moderate degree. The possibility of having it, is the foundation on which we shall see hereafter that induction by simple enumeration38 may in some remarkable42 cases amount practically to proof.[12] No such assurance, however, can be had, on any of the ordinary subjects of scientific inquiry. Popular notions are usually founded on induction by simple enumeration; in science it carries us but a little way. We are forced to begin with it; we must often rely on it provisionally, in the absence of means of more searching investigation43. But, for the accurate study of nature, we require a surer and a more potent44 instrument.
It was, above all, by pointing out the insufficiency of this rude and loose conception of Induction, that Bacon merited the title so generally awarded to him, of Founder45 of the Inductive Philosophy. The value of his own contributions to a more philosophical theory of the subject has certainly been exaggerated. Although (along with some fundamental errors) his writings contain, more or less fully46 developed, several of the most important principles of the Inductive Method, physical investigation has now far outgrown47 the Baconian conception of Induction. Moral and political inquiry, indeed, are as yet far behind that conception. The current and approved modes of reasoning on these subjects are still of the same vicious description against which Bacon protested; the method almost exclusively employed by those professing48 to treat such matters inductively, is the very inductio per enumerationem simplicem which he condemns49; and the experience which we hear so confidently appealed to by all sects51, parties, and interests, is still, in his own emphatic52 words, mera palpatio.
§ 3. In order to a better understanding of the problem [Pg 349]which the logician53 must solve if he would establish a scientific theory of Induction, let us compare a few cases of incorrect inductions with others which are acknowledged to be legitimate. Some, we know, which were believed for centuries to be correct, were nevertheless incorrect. That all swans are white, cannot have been a good induction, since the conclusion has turned out erroneous. The experience, however, on which the conclusion rested, was genuine. From the earliest records, the testimony55 of the inhabitants of the known world was unanimous on the point. The uniform experience, therefore, of the inhabitants of the known world, agreeing in a common result, without one known instance of deviation56 from that result, is not always sufficient to establish a general conclusion.
But let us now turn to an instance apparently57 not very dissimilar to this. Mankind were wrong, it seems, in concluding that all swans were white: are we also wrong, when we conclude that all men's heads grow above their shoulders, and never below, in spite of the conflicting testimony of the naturalist58 Pliny? As there were black swans, though civilized59 people had existed for three thousand years on the earth without meeting with them, may there not also be "men whose heads do grow beneath their shoulders," notwithstanding a rather less perfect unanimity of negative testimony from observers? Most persons would answer No; it was more credible60 that a bird should vary in its colour, than that men should vary in the relative position of their principal organs. And there is no doubt that in so saying they would be right: but to say why they are right, would be impossible, without entering more deeply than is usually done, into the true theory of Induction.
Again, there are cases in which we reckon with the most unfailing confidence upon uniformity, and other cases in which we do not count upon it at all. In some we feel complete assurance that the future will resemble the past, the unknown be precisely similar to the known. In others, however invariable may be the result obtained from the instances which have been observed, we draw from them no more than [Pg 350]a very feeble presumption61 that the like result will hold in all other cases. That a straight line is the shortest distance between two points, we do not doubt to be true even in the region of the fixed62 stars. When a chemist announces the existence and properties of a newly-discovered substance, if we confide50 in his accuracy, we feel assured that the conclusions he has arrived at will hold universally, though the induction be founded but on a single instance. We do not withhold63 our assent16, waiting for a repetition of the experiment; or if we do, it is from a doubt whether the one experiment was properly made, not whether if properly made it would be conclusive. Here, then, is a general law of nature, inferred without hesitation64 from a single instance; an universal proposition from a singular one. Now mark another case, and contrast it with this. Not all the instances which have been observed since the beginning of the world, in support of the general proposition that all crows are black, would be deemed a sufficient presumption of the truth of the proposition, to outweigh65 the testimony of one unexceptionable witness who should affirm that in some region of the earth not fully explored, he had caught and examined a crow, and had found it to be grey.
Why is a single instance, in some cases, sufficient for a complete induction, while in others, myriads66 of concurring67 instances, without a single exception known or presumed, go such a very little way towards establishing an universal proposition? Whoever can answer this question knows more of the philosophy of logic54 than the wisest of the ancients, and has solved the problem of induction.
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1
induction
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| n.感应，感应现象 | |
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distinguished
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| adj.卓越的，杰出的，著名的 | |
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improperly
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| 不正确地，不适当地 | |
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generalization
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| n.普遍性，一般性，概括 | |
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recur
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| vi.复发，重现，再发生 | |
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inadequate
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| adj.(for,to)不充足的，不适当的 | |
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disposition
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| n.性情，性格；意向，倾向；排列，部署 | |
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propensity
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| n.倾向；习性 | |
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pointed
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| adj.尖的，直截了当的 | |
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modifications
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| n.缓和( modification的名词复数 )；限制；更改；改变 | |
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precisely
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| adv.恰好，正好，精确地，细致地 | |
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attaining
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| （通常经过努力）实现( attain的现在分词 )； 达到； 获得； 达到（某年龄、水平、状况） | |
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philosophical
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| adj.哲学家的，哲学上的，达观的 | |
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maxim
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| n.格言，箴言 | |
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generalizations
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| 一般化( generalization的名词复数 )； 普通化； 归纳； 概论 | |
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assent
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| v.批准，认可；n.批准，认可 | |
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assented
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| 同意，赞成( assent的过去式和过去分词 ) | |
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phenomena
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| n.现象 | |
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syllogism
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| n.演绎法，三段论法 | |
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premise
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| n.前提；v.提论，预述 | |
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inductions
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| 归纳（法）( induction的名词复数 )； （电或磁的）感应； 就职； 吸入 | |
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immediate
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| adj.立即的；直接的，最接近的；紧靠的 | |
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nay
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| adv.不；n.反对票，投反对票者 | |
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ratiocination
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| n.推理；推断 | |
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inquiry
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| n.打听，询问，调查，查问 | |
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unanimity
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| n.全体一致，一致同意 | |
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faculty
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| n.才能；学院，系；(学院或系的)全体教学人员 | |
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doctrine
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| n.教义；主义；学说 | |
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applied
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| adj.应用的；v.应用，适用 | |
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defer
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| vt.推迟，拖延；vi.(to)遵从，听从，服从 | |
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controverted
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| v.争论，反驳，否定( controvert的过去式和过去分词 ) | |
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thoroughly
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| adv.完全地，彻底地，十足地 | |
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requisite
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| adj.需要的，必不可少的；n.必需品 | |
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superstition
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| n.迷信，迷信行为 | |
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infinitely
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| adv.无限地，无穷地 | |
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legitimate
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| adj.合法的，合理的，合乎逻辑的；v.使合法 | |
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insufficient
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| adj.(for，of)不足的，不够的 | |
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enumeration
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| n.计数，列举；细目；详表；点查 | |
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conclusive
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| adj.最后的，结论的；确凿的，消除怀疑的 | |
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interrogating
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| n.询问技术v.询问( interrogate的现在分词 )；审问；（在计算机或其他机器上）查询 | |
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purely
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| adv.纯粹地，完全地 | |
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remarkable
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| adj.显著的，异常的，非凡的，值得注意的 | |
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investigation
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| n.调查，调查研究 | |
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potent
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| adj.强有力的，有权势的；有效力的 | |
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Founder
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| n.创始者，缔造者 | |
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fully
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| adv.完全地，全部地，彻底地；充分地 | |
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outgrown
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| 长[发展] 得超过（某物）的范围( outgrow的过去分词 )； 长[发展]得不能再要（某物）； 长得比…快； 生长速度超过 | |
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professing
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| 声称( profess的现在分词 )； 宣称； 公开表明； 信奉 | |
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49
condemns
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| v.（通常因道义上的原因而）谴责( condemn的第三人称单数 )；宣判；宣布…不能使用；迫使…陷于不幸的境地 | |
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confide
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| v.向某人吐露秘密 | |
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sects
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| n.宗派，教派( sect的名词复数 ) | |
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emphatic
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| adj.强调的，着重的；无可置疑的，明显的 | |
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logician
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| n.逻辑学家 | |
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logic
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| n.逻辑(学)；逻辑性 | |
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testimony
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| n.证词；见证，证明 | |
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deviation
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| n.背离，偏离；偏差，偏向；离题 | |
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apparently
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| adv.显然地；表面上，似乎 | |
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naturalist
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| n.博物学家(尤指直接观察动植物者) | |
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civilized
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| a.有教养的，文雅的 | |
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credible
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| adj.可信任的，可靠的 | |
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presumption
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| n.推测，可能性，冒昧，放肆，[法律]推定 | |
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fixed
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| adj.固定的，不变的，准备好的；(计算机)固定的 | |
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withhold
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| v.拒绝，不给；使停止，阻挡 | |
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hesitation
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| n.犹豫，踌躇 | |
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outweigh
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| vt.比...更重，...更重要 | |
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myriads
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| n.无数，极大数量( myriad的名词复数 ) | |
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concurring
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| 同时发生的，并发的 | |
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