DISCUSSION 107 



to disprove. He represents it to himself as an 

 absolutely beneficial design, working out its 

 purpose without reference to any external 

 conditions of evolution. In reality there is 

 in the organisms only a relatively beneficial 

 design, dependent upon definite external 

 influences, and so possessing definite limita- 

 tions. If an organism is brought into unusual, 

 and for it unnatural, surroundings, it is obvious 

 that it will not always act beneficially. Plate 

 has not proved anything against the existence 

 of an immanent directing principle in nature. 



In order to show that merely selection and not 

 design controls the organic world, Professor Plate 

 had recourse to the following simile. ' If an engineer 

 wishes to construct a pump, he follows the principle 

 of natural selection if he puts together the parts 

 of the pump without much consideration, and 

 makes perhaps two hundred pumps in hopes that 

 one or other may chance to answer his purpose. No 

 one would say that a man of this kind acts with 

 design, but this is how nature acts according to the 

 principle of selection.' 



I should like to contrast this picture of 

 Professor Plate's with another, far better suited 

 to illustrate the real relation between design 

 and natural selection. Let us imagine that 

 some company offers a prize for the pump 

 that best answers a given purpose. Various 



