IN MAN'S NEVER-ENDING ENDEAVOUR 



to understand, and thus ultimately to control, 

 the world in which he lives, the theories we as- 

 sociate with the name of Darwin have been among the most 

 important advances in recorded history. It was Darwin's work 

 that persuaded the human race to adopt a view of living crea- 

 tures which at first sight seems complicated and unlikely, but 

 which is really much more profound than the simpler ideas 

 that had reigned previously. In earlier times mankind had in 

 general been content to accept uncritically the picture of the 

 living world he could see when he observed it during his short 

 lifetime. The world appeared to be filled with many different 

 kinds of animals and plants, which formed a number of species 

 between which there were few intermediates. The horse and 

 the ass were two different kinds, with little connection between 

 them. There were, of course, some thinkers before Darwin who 

 maintained that this lack of connection between species was 

 illusory, and that over long periods of time species changed 

 and were in reality connected by sequences of evolutionary 

 alterations. It is, however, to Darwin that the credit must go 

 for presenting the arguments for this conclusion so forcibly 

 that the world as a whole was persuaded that it is correct. It 

 is to him, more than to anyone else, that mankind today owes 

 one of the most fundamental of its beliefs: namely, that the 

 natures of the various living beings in the world are not ele- 

 mentary facts with which mankind is faced, but that the or- 

 ganisms inhabiting the earth's surface have been brought into 

 being by causal processes which are in principle capable of be- 

 ing controlled and directed. 



It followed from the theory of evolution that man himself, 

 who can scarcely deny that he is an animal, must be subject to 

 the laws of evolutionary change which affect all living things. 

 The theory of evolution is therefore inescapably connected with 

 the other systems of thought by which man has attempted to 



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