HYPOTHESIS 137 



analogy with the elastic medium, air, which propagates sound, 

 we could infer nothing at all about it in explanation of the pro 

 pagation of radiant heat and light. If it &quot; were wholly different 

 from anything else known to us, we should in vain try to reason 

 about it&quot;. 1 



But now, granting all this ; granting that if the hypothesis is 

 to be verifiable in this sense, i.e. empirically, by being brought to 

 the test of facts, the supposed cause must have some analogy 

 with known causes ; the question at once arises : Is it always 

 possible to make an hypothesis of this kind ? Or must we not be 

 sometimes satisfied with supposing, as the real cause of the pheno 

 mena under observation, some cause for the conception of which 

 we can have no independent evidence, no analogy to aid us ; for 

 the real presence of which we have no independent evidence, i.e. 

 other than the actual phenomena under investigation ; and about 

 whose nature, therefore, we cannot hope to learn anything further 

 than what we can attribute to it as cause of these phenomena ? The 

 answer is, that certainly we must sometimes be satisfied with this 

 latter sort of supposition. In searching for the immediate causes 

 of the smaller sections of reality examined in the various special 

 sciences, analogies are more abundant. But according as we seek 

 the remoter and wider causes of more extended regions of reality, 

 our sources of analogy must of necessity become fewer and fewer, 

 and we are forced to fall back upon the supposition of causes about 

 whose nature we can get practically no other information than what 

 the study of the effect itself the larger field of phenomena in ques 

 tion will yield us. This is the case with all those wider and more 

 fundamental speculations, or &quot; systematic conceptions,&quot; about the 

 ultimate nature and properties of the phenomenal universe, about 

 the constitution of matter, the cause of gravitation, the arrange 

 ment and motions of the heavenly bodies. Our hypothesis may 

 account sufficiently for all the facts that suggested it ; but who will 

 say that it is the only one that can account for them ? The most 

 we can say is, that of all the alternative hypotheses it is the one 

 that accounts best for the facts ; and this may give us moral 

 certitude that it is the right one, even though, strictly speaking, 

 we cannot pass from the affirmation of consequent to the affirma 

 tion of antecedent unless we know that the latter is the only 

 possible antecedent of the consequent in question. 



1 JKVONS, Principles of Science, p. 512. 



