i859 LETTER TO LYELL 1 87 



It is wholly impossible to prove that any phenomenon what- 

 soever is not produced by the interposition of some unknown 

 cause. But philosophy has prospered exactly as it has disre- 

 garded such possibilities, and has endeavoured to resolve every 

 event by ordinary reasoning. 



I do not exactly see the force of your argument that we 

 are bound to find fossil forms intermediate between men and 

 monkeys in the Rocks. Crocodiles are the highest reptiles as 

 men are the highest mammals, but we find nothing intermediate 

 between crocodilia and laccrtilia in the whole range of the 

 Mesozoic rocks. How do we know that Man is not a persistent 

 type? And as for implements, at this day, and as, I suppose, 

 for the last two or three thousand years at least, the savages of 

 Australia have made their weapons of nothing but bone and 

 wood. Why should Homo Eoccnus or Oolilicus, the fellows 

 who waddied the Amphithcrium and speared the Phascolo- 

 therium as the Australian niggers treat their congeners, have 

 been more advanced? 



I by no means suppose that the transmutation hypothesis is 

 proven or anything like it. But I view it as a powerful instru- 

 ment of research. Follow it out, and it will lead us somewhere ; 

 while the other notion is like all the modifications of " final 

 causation," a barren virgin. 



And I would very strongly urge upon you that it is the 

 logical development of Uniformitarianism, and that its adoption 

 would harmonise the spirit of Paleontology with that of Physical 

 Geology. 



