THE MECHANICAL SYSTEM AND ITS LIMITS 375 



that was poor in oxygen and could only make a 

 sufficient use of the oxygen by sticking together. The 

 imagination has a wide field in these problems, but we 

 cannot say whether the construction of multicellulars 

 only took place once or on several occasions. 



As natural selection is not a force that of itself creates 

 more complex organisms, so it is not an absolute 

 principle of progress. It is scientifically illogical to say 

 that animals are " improved " by natural selection. 

 "Good" and "bad "are antithetic and dualistic terms 

 that have no place in a unified conception of the world. 

 The word " improve " would only have a meaning if we 

 recognised any value in the nature of animals. But 

 that is entirely wrong. The man of science has only to 

 determine the processes of the world and discover their 

 causes. For him there are only changes in the world. 

 There can only be an " improvement " if we recognise 

 an end, the good. Mechanism has nothing to do with 

 ends. 



Even if we could recognise value in the nature of 

 animals, we could never say whether certain changes 

 that we observe in animals are improvements or no. 

 Selection adapts animals to their environment at the 

 moment, and we do not know if these will not change, 

 in which case the opposite modifications will have to be 

 selected. For instance, if the animals with the thickest 

 coats survive in a very cold climate, we cannot say that 

 the selection of the thick coat is an improvement for 

 the animals. If that were so the cold would have to 

 remain unchanged, whereas the climate may become 



