THE PROBLEM OF BODY AND MIND 255 



scientific investigators can entertain; (VI) the theory of animism 

 or the soul -theory; and (VII) the identity hypothesis, or two-aspect 

 theory, or correlation theory. 



A case can be reasonably stated for the theory of psychical 

 monism, for the soul-theory, and for the two-aspect theory, and a 

 decision must be left with the individual according to his personal 

 experience. Each theory has its qwn advantages and its own dif- 

 ficulties. When the biological facts are dominant in the mind the 

 balance will swing towards the ' two-aspect theory ' or ' identity 

 hypothesis,' which regards the living creature as a psycho-physical 

 unity, psychosis and neurosis being two aspects of one and the 

 same continuous life. 



Perhaps, as in the case of vitalism, the most consistent scientific 

 position is to keep firmly to the fact that just as the everyday 

 functions of the organism, not to speak of its development, hered- 

 ity, and evolution, cannot be adequately described in terms of 

 chemico-physical concepts, so it appears that many of the forms of 

 behaviour cannot be adequately described in terms of the concepts 

 of biology. A new aspect of reality is expressed requiring new 

 categories psychological categories. This is but a pedantic way 

 of expressing what was said of old : " Surely the life is more 

 than food." 



