132 ORGANISM AND MECHANISM 



evolution is simply a continuation of a historical inorganic 

 process of increasing differentiation and heterogeneity. It 

 may be continuous with it, but it is not a continuation of 

 it, any more than the evolution of human societary forms 

 is a continuation of the evolution of mammals. The issues 

 changed when organisms began, and again when man began. 

 Moreover, what is called, for instance, the evolution of 

 the solar system should rather be called the development 

 of the solar system, since it is the differentiation of one 

 mass into explicit manifoldness. The originative nebula 

 or whirling mass of planetesimals is comparable to a great 

 world-egg, to borrow Hume's phrase, and we may think of 

 it as developing into several embryos, as eggs sometimes do. 

 But, so far as we know, there was no struggle between the 

 various planets, or between them and their environmental 

 limitations. There was no sifting process which eliminated 

 some and left others surviving. Whether we speak of the 

 history, or differentiation, or development, or evolution of 

 the solar system, we must recognise that it was a very dif- 

 ferent process from organic evolution. In the former there 

 were no alternatives, no trial-and-error methods. There 

 was nothing comparable to the staking of individual lives 

 and losing them which is characteristic of that sublime ad- 

 venture which we call organic evolution. The theory of 

 organic evolution starts with the assumption of variability, 

 which transcends mechanical interpretation and is perhaps 

 least obscure at present when we think of it most anthropo- 

 morphically as experimenting in self-expression. Moreover, 

 the organism is in some measure a genuine agent even in 

 the process of natural selection. It is often anything but 

 a passive pawn. It does not simply submit to the apparently 

 inevitable. It often evades its fate by a change of habit 



