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and to tell her that they know her better than she knows herself. As to the use of hypothesis, and the vanity of blind and unintelligent inquiry at Nature's oracles, no one can be more explicit than Bacon himself; or speak with more contempt of that 'vaga experientia quæ mera palpatio est.' A just image of the empirical philosopher who confounds induction with the 'mera palpatio' would be a man admitted to an immense laboratory of all sorts of chemicals — some more simple and some less and essaying discovery by going round the shelves and amusing himself with pouring a little out of one box or phial into any other, as their proximity or his own eye or fancy suggested, just to see what would come of it. Now if he did not manage to choke himself with some unhappy evolution of gases, of which he had had no 'anticipation,' nor could give any 'interpretation ;' or blind himself with some equally novel and brilliant explosion of inflammable substances; or poison himself with some subtle exhalation, there is no doubt but he might chance to stumble on some singular discovery; upon none, however, greater than the discovery that he would not know what he had discovered. On the other hand, if he made no discovery, nobody would be surprised; nor, lastly, concede him any merit if he did.
We return to the subject postponed a page or two back. Though it is evident that deduction will play a more and more important part as science advances, because it will have wider and wider bases of inference before it, it may still be doubted whether it will ever we do not say supersede, but even much diminish the necessity for induction and experiment; whether, in fact, Descartes' view is not near the truth. One may suspect this, not merely because
(as Mr. Mill properly says) deduction must presuppose and demand induction- not only because the deductive process (to make it worth anything) will ever demand verification, which itself involves an appeal to induction; nor merely because as the data of deductive inference become more and more extensive and complex, the inferences themselves (as the same writer observes) involve an analysis and computations which can rarely be performed with more than approximate accuracy;-not only, we say, for these reasons, but for another and more direct one. It is this: that the results of the deductive process, being rarely more than approximations to complete solution, with whatsoever sagacity and subtlety conducted, will often require to be rectified as well as verified by further observation; the very attempt to verify them will often reveal previously unsuspected residual phenomena, which ought not to exist, if both data and deduction were complete, and suggest an entirely new series of experiments and observations to adjust the theory to the facts.*
Though, therefore, the triumphs of deduction may be continually more splendid, those very triumphs will, in all probability, disclose new fields for the achievements of induction..
In short, in the attempt to unravel completely any considerable portion of the great web of the universe,
* See the striking observations of Mr. J. S. Mill on the subject of the 'Method of Residues,' with the beautiful illustrations from Sir John Herschel. (Mill's Logic, vol. i. p. 501.) Mr. Mill's observations on Residual Phenomena, are made, indeed, in reference to the results of the experimental methods of inquiry; but similar observations seem applicable to many results of the deductive process. See Sir J. Herschel's 'Discourse,' pp. 174-5., for some striking remarks on the alternate use of these instruments.
much more of the whole, induction and deduction may, for aught we know, reciprocally involve one another in an interminable progression;-so far, according to Bacon's sublime language, does the 'subtlety of nature surpass the subtlety either of sense or intellect.' Thus will man be ever tied, as a condition of advancement to observation and experiment; deduction will always be preceded and accompanied by them, and never be independent of them; while the most sagacious conjectures will still end with the Queen of Sheba's exclamation, The half hath not been told me.' And surely man may well be contented with his sublime, though he is sometimes apt to think it, humble office of interpreter of nature. It is enough for him. To what greater glory can the creature aspire than that of being the interpreter of his Creator? to decipher those hieroglyphics which are symbols-though but imperfect symbols-of the Infinite One? There is no sublimer passage of poetry in the world than that in Job (to which far from justice is done in our translation), in which the Patriarch, after having enumerated even the splendours with which God has 'garnished the heavens,' and the art with which He has 'hung the world upon nothing,' exclaims, 'How slight is the whisper that we hear of him! But the thunder of his power who can comprehend?'
Even the felt necessity, however, of verification, for every result of deduction, shows how completely, from the very constitution of his nature, man is tied down to experiment and observation; and how, unless these authenticate his 'anticipations,' all he achieves by the other instrument goes for nought, if it is to pass as a declaration of what is. Take the case of Halley's wonderful prophecy of the periodic time of what is naturally called his comet. If we may sup
pose (what was by no means impossible) that during several successive years of its predicted return, clouds had obstinately filled the sky, and concealed it from the astronomer's gaze, would the world have given absolute faith to the predictions? No verily; it would have been said, 'If the comet does indeed move in the exact path and observe the prescribed laws of your calculation, it will have returned, though we saw it not; but there are so many unknown causes,' (some, indeed, which modify Halley's anticipations have been discovered since,) 'which may vitiate the result, that we cannot accept it as a fact, till we observe the comet's return. Your calculations are all hypothetically true; they tell us what may be, but they must not assure us of what is, till fact itself has confirmed them.'
The rules which Descartes, as well as Bacon, have given for the prosecution of scientific discovery-the one more particularly in relation to the process of induction, and the other to that of deduction-may seem of very little use as directly applied to the purposes for which they were more immediately designed; and perhaps no great discovery was ever made by the mechanical or deliberately conscious application of the rules of either. Yet it would be a fallacious conclusion that they are of no utility at all; and far greater would be the error of concluding the like in relation to the general observations (such as those in the immortal first book of the NOVUM ORGANUM), which tend to forewarn the mind itself of the points in which an ambush of error may be suspected; to guard it against the easily besetting prejudices which spring from its very constitution, or have been contracted in the course of its development; and to remind it during the course or in the review of its operations, to ask
whether certain points have been guarded, certain cautions observed, certain known conditions complied with. Such observations, when well founded, however unsusceptible of a direct application to the discovery of an unknown truth, or explanation of an unknown phenomenon, tend by a general influence to rectify the position of the mind. They are not (if we may borrow a metaphor from astronomy) the telescope by which the star we seek is revealed, but they enable us, as astronomers say, to allow for the aberration of light, and to adjust the instrument in the right position for observation. There are some admirable sentences in Mill's Logic applicable to this subject. There is not,' says he, 'properly an Art of Observing. There may be rules for observing. But these, like rules for inventing, are properly instructions for the preparation of one's own mind; for putting it into the state in which it will be most fitted to observe, or most likely to invent. They are, therefore, essentially rules of self-education, which is a different thing from Logic. They do not teach how to do the thing, but how to make ourselves capable of doing it. They are an art of strengthening the limbs, not an art of using them.'
Viewed in any other light, the four meagre rules of Descartes mentioned in his 'Method,' or even the more elaborate one and twenty in his posthumous 'Règles pour la direction de l'esprit,' seem rather
* This work contains many admirable observations of that more general character to which we have above adverted; tending to enlarge and rectify the conceptions under which the mind. may set about philosophising; to exercise a pervading influence over the habits of thought; to inspire, in a word, the philosophic spirit. Considered as a specific apparatus designed for conscious application in the attempt to elicit scientific truth, it is, for the