26 THE MECHANISTIC THEORY OF LIFE 



appears to be something in a living organism 

 which acts, within limits, independently of 

 the physical and chemical conditions of en 

 vironment. The apparent autonomous selec- 



t tive action of the organism turns out to 

 be causally dependent in every detail on 

 physical and chemical conditions. The vital 

 principle, if it exists, is therefore determined 

 in its action by those conditions : we can 

 never isolate and clearly identify its action. 

 As a positive scientific working hypothesis it 



. is thus useless ; at the best it only serves to 

 express our ignorance of the exact means by 

 which the parts of a living organism are 

 caused to react in a certain manner to a given 

 physical or chemical change. This being so, 

 the advocates of the mechanistic theory may 

 well ask whether vitalism has any real 

 justification. 



To illustrate the force of this question it 

 is only necessary to refer to the main argu 

 ment for vitalism in the recent writings of 

 Driesch. As is well known he discovered 

 that in the earliest stages of embryonic 

 development the cells of the embryo may be 

 separated completely from one another, or 



