LAWS OF NATURE. 233 



or with conclusions capable of being correctly deduced from thcni, then, 

 unless on reconsideration it should appear that some of the stronger induc- 

 tions have been expressed with greater universality than their evidence 

 warrants, the weaker one must give way. The opinion so long prevalent 

 that a comet, or any other unusual appearance in the heavenly regions, was 

 the precursor of calamities to mankind, or to those at least who witnessed 

 it; the belief in the veracity of the oracles of Delphi or Dodona; tlie reli- 

 ance on astrology, or on the weather-prophecies in almanacs, were doubt- 

 less inductions supposed to be grounded on experience:* and faith in such 

 delusions seems quite capable of holding out against a great multitude of 

 failures, provided it be nourished by a reasonable number of casual coinci- 

 dences between the prediction and the event. What has really put an end 

 to these insufficient inductions, is their inconsistency with the stronger in- 

 ductions subsequently obtained by scientific inquiry, respecting the causes 

 on which 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 connected by ratiocination, are confirmatory 

 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 in- 

 creased in certainty. Thus the Torricellian experiment, though a mere 

 case of three more general laws, not only strengthened greatly the evidence 

 on which those laws i-ested, but converted one of them (the weight of the 

 atmosphere) from a still doubtful generalization into a completely estab- 

 lished doctrine. 



If, then, a survey of the uniformities which have been ascertained to ex- 

 ist in nature, should point out some which, as far as any human purpose re- 

 quires certainty, may be considered quite certain and quite universal; then 

 by means of these uniformities we may be able to raise multitudes of other 

 inductions to the same point in the scale. For if we can show, with re- 



* Dr. Whewell {Phil, of Discov., p. 246) will not allow these and similar erroneous judg- 

 ments to be called inductions; inasmuch as such superstitious fancies "were not collected 

 from the fects by seeking a law of their occurrence, but were suggested by an imagination of 

 the anger of superior powers, shown 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 be- 

 lievers in these erroneous opinions had been put on their defense, they would have referred 

 to experience : to the comet which preceded the assassination of Julius Cassar, or to oracles 

 and other prophecies known to have been fulfilled. It is by such appeals to facts that all 

 analogous supei'stitions, even in our day, attempt to justify themselves ; the supposed evi- 

 dence of experience is necessary to their hold on the mind. I quite admit that the influence 

 of such coincidences would not be what it is, if strength were not lent to it by an antecedent 

 presumption ; but this is not peculiar to such cases ; preconceived notions of probability form 

 part of the explanation of many other cases of belief on insufficient evidence. The a priori 

 prejudice does not prevent the erroneous opinion from being sincerely regarded as a legiti- 

 mate conclusion from experience ; though it improperly predisposes the mind to that inter- 

 pretation of experience. 



Thus much in defense of the sort of examples objected to. But it would be easy to pro- 

 duce instances, equally adapted to the purpose, and in which no antecedent prejudice is at all 

 concerned. "For many ages," says Archbishop Whately, "all farmers 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. 



