FALLACIES OF GENERALIZATION. 357 



for aught we know, may be entirely different, or may succeed 

 one another according to different laws, or even according to 

 no fixed law at all. Such, again, in matters dependent on 

 causation, are all universal negatives, all propositions that 

 assert impossibility. The non-existence of any given pheno- 

 menon, however uniformly experience may as yet have testi- 

 fied to the fact, proves at most that no cause, adequate to its 

 production, has yet manifested itself; but that no such causes 

 exist in nature can only be inferred if we are so foolish as 

 to suppose that we know all the forces in nature. The sup- 

 position would at least be premature while our acquaintance 

 with some even of those which we do know is so extremely 

 recent. And however much our knowledge of nature may 

 hereafter be extended, it is not easy to see how that know- 

 ledge could ever be complete, or how, if it were, we could ever 

 be assured of its being so. 



The only laws of nature which afford sufficient warrant 

 for attributing impossibility (even with reference to the exist- 

 ing order of nature, and to our own region of the universe), 

 are first, those of number and extension, which are para- 

 mount to the laws of the succession of phenomena, and not 

 exposed to the agency of counteracting causes ; and secondly, 

 the universal law of causality itself. That no variation in 

 any effect or consequent will take place while the whole of 

 the antecedents remain the same, may be affirmed with full 

 assurance. But, that the addition of some new antecedent 

 might not entirely alter and subvert the accustomed conse- 

 quent, or that antecedents competent to do this do not exist 

 in nature, we are in no case empowered positively to con- 

 clude. 



3. It is next to be remarked that all generalizations 

 which profess, like the theories of Thales, Democritus, and 

 others of the early Greek speculators, to resolve all things 

 into some one element, or like many modern theories, to 

 resolve phenomena radically different into the same, are neces- 

 sarily false. By radically different phenomena I mean impres- 

 sions on our senses which differ in quality, and not merely 



