48 THE STORY OF THE LIVING MACHINE. 



proves that mental power is dependent upon brain 

 structure. Further, it is found that certain visible 

 changes occur in certain parts of the brain the 

 brain cells when they are excited into mental ac- 

 tivity. Such series of facts point to an association 

 between the mental side of sensations and physical 

 structure of the machine. But they do not prove 

 any correlation between them. The unlikeness of 

 mental and physical phenomena is so absolute 

 that we must hesitate about drawing any connec- 

 tion between them. It is impossible to conceive 

 the mental side of a sensation as a form of wave 

 motion. If, further, we take into consideration the 

 other phenomena associated with the nervous sys- 

 tem, the more distinctly mental processes, we have 

 absolutely no data for any comparison. We can 

 not imagine thought measured by units, and until 

 we can conceive of such measurement we can get 

 no meaning from any attempt to find a correlation 

 between mental and physical phenomena. It is 

 true that certain psychologists have tried to build 

 up a conception of the physical nature of mind; 

 but their attempts have chiefly resulted in building 

 up a conception of the physical nature of the brain, 

 and then ignoring the radical chasm that exists 

 between mind and matter. The possibility of de- 

 scribing a complex brain as growing parallel to the 

 growth of a complex mind has been regarded as 

 equivalent to proving their identity. All attempts 

 in this direction thus far have simply ignored the 

 fact that the stimulation of a nerve, a purely phys- 

 ical process, is not the same thing as a mental ac- 

 tion. What the future may disclose it is hazardous 

 to say, but at present the mental side of the liv- 

 ing machine has not been included within the con- 

 ception of the mechanical nature of the organism. 



