146 The Evolution Hypothesis. 



the reasoning. In this field it is difficult to hide in- 

 conclusive thinking under the mist of generalities: 

 mathematical reasoning does not admit of the substi- 

 tution of illustrations for arguments and doubtful 

 analogies for conclusive proofs. 



We are not, perhaps, pressing too far some indica- 

 tions in his works, if we infer that Mr. Spencer has not 

 in this department arrived as yet at conclusions that 

 could be established by incontestable reasoning. We 

 find him admitting that " the antecedents of those 

 forces which our solar system displays belong to a 

 past of which we can never have anything but in- 

 ferential knowledge ; and at present we cannot be said 

 to have even this. Numerous and strong as are the 

 reasons for believing the nebular hypothesis, we can- 

 not yet regard it as more than an hypothesis"* But if 

 the nebular hypothesis be still doubtful ; if we cannot 

 be said to have even " inferential knowledge " of it, 

 the same dubiety attaches to the evolution hypo- 

 thesis ; for the existence of a nebulous mass gradually 

 passing, by the operation of dynamic law, into the 

 present state of the universe is essential to the evolu- 

 tion doctrine. 



Not having before us a detailed exposition of the 

 application of the evolution hypothesis to the pro- 

 cesses of cosmic change, we must content ourselves by 

 examining it in its answer to questions that lie at the 



* First Principles, 68. 



