THE CONCEPTUAL WORLD 3 



have been propagated along the sensory nerves, and 

 must have reached the brain, affecting masses of 

 nerve cells there. Nothing in physiology seems to 

 indicate that we can inhibit or repress the activity 

 of the distance sense-receptors, visual, auditory, and 

 olfactory, with their central connections in the brain ; 

 they must have functioned, and must have been 

 physically affected by the events that took place out- 

 side ourselves, and yet we were unconscious, in the 

 fullest sense of this term, of all this activity. Why 

 is it, then, that our perception was so much less than 

 the actual physical reception of external stimuli that we 

 must postulate as having occurred ? Sherlock Holmes 

 would have said that we really saw and heard all these 

 things although we did not observe them, but the full 

 explanation involves a much more careful consideration 

 of the phenomena of perception than this saying 

 indicates. 



There is, of course, no doubt that we did see and 

 hear and smell all the things that occurred in the street 

 during our aimless peregrination, that is, all the things 

 which so happened that they were capable of affecting 

 our organs of sense. This is true if we mean by seeing 

 and hearing and smelling merely the stimulation of 

 the nerve-endings of the visual, auditory, and olfactory 

 organs, and the conduction into the brain of the 

 nervous impulses so set up. But merely to be stimu- 

 lated is only a part of the full activity of the brain ; the 

 stimulus transmitted from the receptor organs must 

 result in some kind of bodily activity if it is to affect 

 our stream of consciousness. Two main kinds of 

 activity are induced by the stimulation of a receptor 

 organ and a central ganglion, (i) those which we call 

 reflex actions, and (2) those actions which we re- 

 cognise as resulting from deliberation. We must now 



