INTRODUCTION xv 



Helmholtz indeed acknowledged that all objects must 

 appear different to each subject ; but he was seeking 

 the reality behind appearances. Many have done this 

 before him : but he differed from his predecessors in 

 supposing that what lies behind appearance is not the 

 *' Weltgeist," but the physical laws of the universe. 

 That is a matter of taste. 



Helmholtz remained consistently a physicist even in 

 extremes, and his exceptional genius paved the way for 

 materialism, whether he would or no, since it invested 

 physics with an unmerited halo. 



No attempt to discover the reality behind the world 

 of appearance, i.e. by neglecting the subject, has ever 

 come to anything, because the subject plays the decisive 

 role in constructing the world of appearance, and on the 

 far side of that world there is no world at all. 



All reality is subjective appearance. This must con- 

 stitute the great, fundamental admission even of biology. 

 It is utterly vain to go seeking through the world for 

 causes that are independent of the subject ; we always 

 come up against objects, which owe their construction 

 to the subject. 



When we admit that objects are appearances that 

 owe their construction to a subject, we tread on firm 

 and ancient ground, especially prepared by Kant to 

 bear the edifice of the whole of natural science. Kant 

 set the subject, man, over against objects, and discovered 

 the fundamental principles according to which objects 

 are built up by our mind. 



The task of biology consists in expanding in two 

 directions the results of Kant's investigations: — (i) by 

 considering the part played by our body, and especially 

 by our sense-organs and central nervous system, and 

 (2) by studying the relations of other subjects (animals) 

 to objects. 



To make things easier to understand, I shall first 

 of all endeavour to reproduce in current biological 

 terminology the main results of Kant's line of research. 



It is Kant's undying merit to have discovered an 

 organisation in our subject, and to have revealed its 



