V 



3i6 THEORETICAL BIOLOGY 



Karl Ernst von Baer, who in his day investigated this 

 problem very thoroughly, also decided to deny purposeful- 

 ness in Nature altogether. Instead of " purpose," he declared 

 that " goal " was the decisive thing. We can make Baer's 

 idea clear to ourselves by an example that he selected. When 

 a bullet leaves the barrel of a gun and hits the target, the 

 target is the factor that prescribes the path for the ball. If 

 we imagine the act of shooting to be eliminated, we must 

 ascribe to the ball itself the property of being influenced 

 directly by the target in the direction its movement takes. 

 In such a case the ball possesses what Baer calls " effort 

 towards a goal." 



In the same way, Baer declares that the embryo displays 

 effort towards a goal. Considering the time at which he was 

 writing, this presentation of the matter was quite correct. 

 It suffered, however, from the circumstance that the target 

 was placed too near. If what we have in mind is not the full- 

 grown body, but its congruity with the surrounding-world, 

 then the environment becomes the goal into which the body 

 with all its receptors and effectors has to grow. But from 

 the surrounding-world, namely the inorganic medium, no 

 influence can proceed enabling the germ to follow a definite 

 course during its development. A direct reciprocal effect 

 between germ and surrounding-world, such as the doctrine 

 of effort towards a goal presupposes, cannot be assumed. 

 The main difficulty — namely, the congruity of organism 

 and environment — is not solved by effort towards a goal. 



If we could ascribe to the environment all properties, 

 and these in their full degree, the solution would be simple. 

 Then every shape assumed by the animal would straightway 

 be in congruity with the outer world. But things are not so. 

 When an animal gets into a strange environment, it is usually 

 unable to make a suitable surrounding-world for itself, 

 and, because it cannot fit in, it perishes. The external world. 



