RESPIRATION 399 



of the maintenance of organic identity. Up to a certain point one 

 can apply the same reasoning to conscious activities by showing 

 how exquisitely dependent they are from moment to moment on 

 the integrity of normal "conditions of life" in the internal en- 

 vironment, and how they play their part in maintaining this in- 

 tegrity in accordance with Claude Bernard's conception. But such 

 treatment of them is wholly insufficient, since they evidently par- 

 ticipate in that spiritual world to which reference has already 

 been made. Hence they cannot be described in terms of the work- 

 ing hypotheses of biology, and attempts to describe them ade- 

 quately in such terms are merely childish. A fortiori they cannot 

 be described in physical terms. 



Perception and volition are often referred to as processes occur- 

 ring in the cerebral hemispheres as a result of physical impulses 

 communicated along sensory nerves from outside. For certain 

 limited practical purposes this is a useful view to take of them. 

 But, as already pointed out, perception and volition as such are 

 not capable of description as events occurring at a certain time and 

 place, since from their very nature they include other times and 

 places, and may be said to be creative of time and space. The 

 working conception under which we attempt to describe them as 

 events occurring here and now is totally inadequate; and in so 

 far as we express them in terms of this conception we reduce them 

 to mere abstractions. By a process of abstraction we can observe 

 in ourselves and interpret as mere physiological or even physical 

 events our perceptions and voluntary actions. These observations 

 constitute an important part of our existing practical knowledge, 

 but they belong to physics or physiology, and not to psychology, 

 since in making them we deliberately leave out of account all that 

 is characteristic of conscious activity. 



To those who argue that all our conscious activities are depend- 

 ent on physical conditions, the reply is that "physical conditions" 

 are in ultimate analysis only imperfect abstractions. If once we re- 

 gard them as anything more, we are plunged into all the difficul- 

 ties which modern philosophy since Descartes has been continu- 

 ously and successfully grappling with. The universe is a spiritual 

 universe, and not a dualistic universe of matter and mind. 



This book is concerned with physiology and not psychology. 

 I have claimed for physiology its rightful practical sphere in 

 distinction from that of physics and chemistry. But we have 

 reached a limit to the sphere of physiology when we come to deal 

 with conscious activity. 



