Mental Processes in Man. 307 



they seem also to differ in place. A sensation of touch 

 may be referred to different parts of the body the hand, 

 the foot, or the forehead. But here we open up an im- 

 portant question Where do we feel a sensation, such as, 

 for example, that of pressure on the skin ? Common sense 

 answers, without hesitation, that we feel it at the particular 

 part of the body which is affected by the external stimulus. 

 I feel the pen with which I write with my finger-tips. And 

 common sense is perfectly right from its own point of 

 view. But it is a well-known fact that a person whose leg 

 has been amputated experiences at times tickling and 

 uneasiness in the absent member. This is due to irritation 

 of the nerve-ends in the stump of the limb. But the 

 sensations are referred outwards to the normal source of 

 origin of impressions, the effects of which were carried 

 inwards by the nerve affected. We shall have to consider 

 hereafter the nature of the relation between physiological 

 and psychological processes the connection of mind and 

 body. Assuming for the present that psychical processes 

 have a physical basis in physiological processes, the fact 

 given above and others of like implication seem to show 

 that the sensation has for its physiological basis some 

 nerve-change in the central nervous system in us, no 

 doubt, in the brain. Of course, it must be remembered 

 that the sensation, as felt, is a mental fact (using the word 

 " mental " in its broadest sense, as belonging to the 

 psychical as opposed to the physiological series). But it 

 would seem that the physiological accompaniment of this 

 mental fact is some nerve-change in the brain. This 

 nerve-change is caused by a stimulus having its origin in 

 the end-organ of the afferent nerve, and we naturally refer 

 the impression outwards to the place of its source of origin 

 under ordinary and normal conditions. In other words, 

 we localize it. That is what common sense means when it 

 says that we feel pressure at the finger-tips. 



To account for this process of localization, it is supposed 

 that every sensation, apart from its special quality as a 

 touch, a taste, or a smell, has a more or less defined 



