390 INDUCTION. 



is their inconsistency with the stronger inductions 

 subsequently obtained by scientific inquiry, respecting 

 the causes upon which terrestrial events really depend ; 

 and where those scientific truths have not yet pene- 

 trated, 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 together by a ratiocination, are confirma- 

 tory of one another : while any which lead deductively 

 to consequences that are incompatible, become mutu- 

 ally 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 ratiocina- 

 tion 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 cer- 

 tainty. Thus 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 doubtful generalization into 

 one of the best- established doctrines in the range of 

 physical science. 



If, then, a survey of the uniformities which have 

 been ascertained to exist in nature, should point out 

 some which, as far as any human purpose requires 

 certainty, may be considered" as absolutely certain 

 and absolutely 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 respect to any induction, that 

 either it must be true, or one of these certain and 

 universal inductions must admit of an exception; the 

 former generalization will attain the same absolute 



