210 



INDUCTION. 



potism. The strong induction becomes 

 still stronger when a weaker one has 

 been bound up with it. 



On the other hand, if an induction 

 conflicts with stronger inductions, or 

 with conclusions capable of being 

 correctly deduced from them, then, 

 unless on reconsideration it should 

 appear that some of the stronger 

 inductions have been expressed with 

 greater universality than their evi- 

 dence warrants, the weaker one must 

 give way. The opinion so long pre- 

 valent that a comet or any other 

 unusual appearance in the heavenly 

 regions was the precursor of calami- 

 ties to mankind, or to those at least 

 who witnessed it ; the belief in the 

 veracity of the oracles of Delphi or 

 Dodona ; the reliance on astrology, 

 or on the weather-prophecies in al- 

 manacks, were doubtless inductions 

 supposed to be grounded on experi- 

 ence ; * and faith in such delusions 

 seems quite capable of holding out 

 against a great multitude of failures, 

 provided it be nourished by a reason- 

 able number of casual coincidences 

 between the prediction and the event. 

 What has really put an end to these 

 insufficient inductions is their incon- 

 sistency with the stronger inductions 

 subsequently obtained by scientific in- 

 quiry, respecting the causes on which 



* Dr. Whewell (Phil, of Discov., p. 246) 

 will not allow these and similar erroueous 

 judgments to be called inductions, inas- 

 much as such superstitious fancies "were 

 not collected from the facts by seeking a 

 law of their occurrence, but were suggested 

 by an imagination of the anger of superior 

 powers, sliown by such deviations from 

 the ordinary course of nature. ' I conceive 

 the question to be, not in what manner 

 these notions were at first suggested, but 

 by what evidence they have, from time to 

 time, been supposed to be substantiated. 

 If the believers in these erroneous opinions 

 had been put on their defence, they would 

 have referred to experience : to the comet 

 which preceded the assjissination of Julius 

 Csesar, or to oracles and other prophecies 

 known to have been fulfilled. It is by 

 such appeals to facts that all analogous 

 superstitions, even in our day, attempt to 

 justify tliemselves ; the supposed evidence 

 of experience is necessary to their hold on 

 the mind. I quite admit that the influence 

 of such coincidences would not be. what it 



terrestrial events really depend ; and 

 where those scientific truths have not 

 yet penetrated, the same or similar 

 delusions still prevail. 



It may be affirmed as a general 

 principle, that all inductions, whether 

 strong or weak, which can be con- 

 nected by ratiocination, are confirma- 

 tory of one another ; while any which 

 lead deductively to consequences that 

 are incompatible become mutually 

 each other's test, showing that one 

 or other must be given up, or at 

 least more guardedly expressed. In 

 the case of inductions which confirm 

 each other, the one which becomes a 

 conclusion from ratiocination rises to 

 at least the level of certainty of the 

 weakest of those from which it is 

 deduced ; while in general all are 

 more or less increased in certainty. 

 Tjjus the Torricellian experiment, 

 though a mere case of three more 

 general laws, not only strengthened 

 greatly the evidence on which those 

 laws rested, but converted one of 

 them (the weight of the atmosphere) 

 from a still doubtful generalisation 

 into a completely established doctrine. 



If, then, a survey of the uniformi- 

 ties which have been ascertained to 

 exist in nature should point out some 

 which, as far as any human purpose 

 requires certainty, may be considered 



is if strength were not lent to it by an 

 antecedent presumption ; but this is not 

 peculiar to such cases; preconceived no- 

 tions of probability form part of the ex- 

 planation of many other cases of belief on 

 insuflacient evidence. The a priori pre- 

 judice does not prevent the erroneous 

 opinion from being sincerely regarded as a 

 legitimate conclusion from experience ; 

 though it improperly predisposes the mind 

 to that interpretation of experience. 



Thus much in defence of the sort of 

 examples objected to. But it would be 

 easy to produce instances, equally adapted 

 to the purpose, and in which no antecedent 

 prejudice is at all concerned. " For many 

 ages," says Archbishop Whately, "all far- 

 mers and gardeners were firmly convinced 

 — and convinced of their knowing it by 

 experience — that the crops would never 

 turn out good unless the seed were sown 

 during the increase of the moon." This 

 was induction, but bad induction ; just as 

 a vicious syllogism is reasoning, but bad 

 reasoning. 



