The Implications of Trial and Error 161 



pie of selection will account, directly or indirectly, 

 for whatever there is of purposiveness in organiza- 

 tion and behavior is of course an open question. 

 But there is no other factor which is certainly opera* 

 tive in shaping descent along adaptive lines, and as 

 entities are not to be multiplied beyond necessity," 

 it is, I believe, justifiable to adhere to th& theory 

 of selection until its inadequacy is clearly established. 



The position to which we are led is that the se- 

 curing of any advantage through the method of trial 

 and error presupposes congenital modes of response 

 which are adapted to secure the welfare of the in- 

 dividual. The method is not the primary source 

 of adaptive reactions so far as the individual is 

 concerned. It cannot be the primary source of adap- 

 tive behavior in the evolution of the race. A method 

 of blundering into success instead >of attaining v it 

 directly, it would be of no service unless the or- 

 ganism were capable of turning to profit its fortu- 

 nate trial movement. In order to do this the or- 

 ganism must be provided for the situation by its 

 inherited endowment. 



Certain writers on -genetic psychology have at- 

 tempted to explain the beginnings of adaptive re- 

 actions on the basis of individual experience alone. 

 Given an organism which just responded to stimuli 

 in a perfectly random manner, they attempt to show 

 how the environment would discipline it into acting 

 in accordance with its own welfare. Aside from 

 those functions which Jensen has included under the 



