46 THE PHILOSOPHY OF BIOLOGY 



marked gap separates these slight individual deviations 

 in the images seen by normal individuals from the 

 large deviations seen by those whose perceptions are 

 what we call pathological ones. The normal universe 

 common to the majority of men and women is an 

 aggregate of molecules in motion. But this is a 

 conclusion with which modern physics has been unable 

 to remain content, for molecules must be able to act 

 on each other across empty space, and this is incon- 

 ceivable. The universe therefore consists of a homo- 

 geneous immaterial medium, the ether of space, and 

 this is the true substantia physica. Molecules and 

 radiation are conditions of the ether, and for the 

 physicist it is the only reality. The ' materialism ' 

 of our own time is therefore the belief in the existence, 

 unconditioned by time or anything else, of the ether, 

 or physical continuum ; a homogeneous medium, of 

 which matter and energy, and the consciousness of 

 the organism, are only states or conditions. 



The materialism of the twentieth century, like the 

 idealism of Berkeley, thus rinds that there is something 

 outside our own consciousness that possesses absolute 

 existence. To the materialist it is the ether of space, 

 and to Berkeley it is the existence of absolute Mind. 

 But if our desire to avoid metaphysics is a genuine one, 

 we must reject the notion of the universal ether no 

 less than we must reject the notion of an absolute 

 Mind, and we must rest content with pure phenomenal- 

 ism. For each of us there can be no existence except 

 that which is perceived or conceptualised. There is 

 nothing but our own consciousness ; there cannot even 

 be an Ego which perceives ; there is only perception. 

 We never do really believe this in spite of our profes- 

 sions of reason. We find on strict self-analysis that 

 we believe that there is an Ego that perceives and 



