350 DARWINISM AND THE PROBLEMS OF LIFE 



lightning by showing that electricity is generated by the 

 friction of certain bodies, that from this a luminous 

 spark must arise, and that these conditions are realised 

 in a storm. 



In the same way we give the most satisfactory 

 explanation of the phenomena of life when we trace 

 them to the known processes of physics and chemistry. 

 However, our actual biological knowledge is much too 

 scanty for us to give this explanation in full. But we 

 may ask if it is possible in a general way to give a 

 physico - chemical explanation of the processes of life, 

 or if it is not in the very nature of life to elude such an 

 explanation. Here we find two contradictory opinions. 

 One holds that a physico-chemical explanation of life 

 is possible ; that is mechanism. The other denies that 

 it is possible ; this system is known as vitalism. 



All that we have said hitherto was based on the 

 mechanical conception. The principle of natural 

 selection, which we have chiefly employed, enabled us 

 to give a mechanical interpretation of the organic world. 

 If living things came into existence and were trans- 

 formed by natural selection, we need only physico- 

 chemical forces to explain the process. 



The Vitalists say, however, that natural selection is 

 just as incapable as any other mechanical principle to 

 explain life. Let us see which property of organisms 

 it is that the Vitalists declare to be particularly 

 inexplicable by physico-chemical means. 



In the first place, they object that the Mechanicists 

 have never yet succeeded in giving a purely physico- 

 chemical explanation of the vital phenomena. But this 



