640 Studies in the Theory of Descent. 



It cannot be raised as an objection that even 

 for the explanation of individual life a vital power 

 was long ago admitted, as there was not then 

 sufficient material at hand to enable the phe- 

 nomena of life to be traced to physical forces. It 

 is now no longer questionable that this assumption 

 was a useless error a false method at the time 

 when made certainly very excusable, since the 

 aspect of the question was then, owing to the 

 imperfect basis of facts, very different to the 

 present analogous question as to the causes of 

 derivative development. Thus, although it is now 

 easy to prove this assumption to be erroneous, it 

 was in the former sense correct, as it was in 

 accordance with the existing state of knowledge. 

 At that time there was hardly one of the numerous 

 bridges which now connect inorganic with organic 

 nature, so that the supposition that life depended 

 upon forces which had no existence outside living 

 beings was sufficiently near. 



In any case the philosophers of that period 

 cannot be blamed for filling up the gaps in the 

 existing knowledge by unknown powers, and in 

 this manner seeking to establish a finished system. 

 The task of philosophy is different to that of 

 natural science ; the former strives at every period 

 to set up a completely finished representation of 

 the universe in accordance with the existing state 

 of knowledge. Natural science on the other hand 

 is only concerned in collecting this knowledge ; 



