28 DEVELOPMENT AND PURPOSE CHAP, n 



sides of the relation, and by so doing we may justly extend 

 our conception of the psychical life on the one side just as 

 we extend the physical life on the other. 



The physical processes associated with consciousness are 

 changes of the nature of which very little is known in the 

 mass of interconnected nerve cells and fibres constituting 

 the hemispheres of the brain. There is no known differ- 

 ence of fundamental quality between these processes and 

 those which go forward in lower nerve centres, and which 

 are not normally attended by consciousness, while there are 

 many acts which are performed sometimes consciously, at 

 other times, if attention is otherwise occupied, uncon- 

 sciously. It is a fair inference that on the physical side 

 there is no gulf between the processes attended by con- 

 sciousness and those not so attended. But we have already 

 seen that on the mental side there is true continuity of 

 character, the conscious shading off from the clear light 

 through every gradation of dimness to the utter dark, 

 while that which was dark- may under new conditions enter 

 into the light. The inference is that organic processes 

 which do not involve clear consciousness may yet include a 

 psychical element, or, more accurately, that the psychical 

 concomitant of neural process may be regarded as varying 

 from a maximum to a zero point, which is perhaps reached 

 in the cases which we shall find in which a reaction has 

 become once for all stereotyped. Thus we may take the 

 psycho-physical whole as a continuous unity, the differences 

 within which are either differences of degree or at most 

 differences of species within a genus. Our business then 

 is to consider the general character of the behaviour of this 

 unity, and then to set out the specific differences of its 

 functions in such a way as to exhibit the various phases of 

 the psychical factor from its lowest to its highest forms. 



