FALLACIES OF GENERALIZATION. 407 



all inferences from the order of nature existing on the 

 earth, or in the solar system, to that which may exist 

 in remote parts of the universe ; where the phenomena, 

 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 phenomenon, how- 

 ever uniformly experience may as yet have testified 

 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 

 commit the absurdity of supposing that we know all 

 the forces in nature. The supposition 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 

 knowledge 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, are first, those 

 of number and extension, which are paramount 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 varia- 

 tion 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 consequent, or that 

 antecedents competent to do this do not exist in 

 nature, we are in no case empowered positively to 

 conclude. 



