THE RELATION OF MIND AND BODY 293 



the supply be quickly restored. Make some other minute 

 alteration in the chemical composition of the blood and a 

 man's behaviour is completely altered : he ma} 7 be reduced to 

 below the level of a beast. We are in this way forced to admit 

 that if there be a soul, all its manifestations are dependent on 

 physical conditions ; and this being so, it seems scarcely worth 

 arguing whether, as the vitalists and (to use Dr. McDougall's 

 term) "animists" maintain, there is something else in a man 

 or animal apart from physical phenomena mysteriously accom- 

 panied by gleams of consciousness. 



It is the premises of this argument which I wish to examine ; 

 indeed there must be examined with the utmost care if ever the 

 two sciences of biology and psychology are to be set on a firm 

 theoretical basis. Living, as we do, in a time when physical 

 conceptions are on all hands tacitly or explicitly assumed to 

 correspond to the reality of our visible universe, it is difficult 

 to obtain a popular hearing for any doubts on the subject ; and 

 even from the philosophical side there comes the argument that, 

 unreal in ultimate analysis as the physical universe is, physical 

 conceptions are nevertheless the forms under which alone such 

 knowledge as we possess is possible. 



Now it seems to me very clear that in the case of living 

 organisms and their physiological environment, we cannot 

 express the observed facts by means of physical and chemical 

 conceptions but must and do have recourse to the conception 

 of organic unity ; and must use this conception as our funda- 

 mental working hypothesis just as the physicist uses the 

 conceptions of matter and energy. This means nothing less 

 than a definite break all along the line, including the environ- 

 ment, with the purely physical conception of nature. We may, 

 it is true, endeavour to give a physical description of the 

 phenomena of life ; but such attempted description cannot 

 express the main facts. 1 The time at my disposal does not 



1 In his Address as President of the British Association Prof. Schafer deals 

 with "The Nature, Origin and Maintenance of Life " and defends the thesis that 

 "the problems of life are problems of matter." Needless to say, I am unable to 

 accept his general conclusions. It appears to me that he has failed to apprehend 

 correctly the general trend of biological advance, particularly during the last fifty 

 years ; and that he completely ignores the fundamental difficulties involved in 

 a physico-chemical conception of life. Living organisms are distinguished from 

 everything else that we at present know by the fact that they maintain and 

 reproduce themselves with their characteristic structure and activities. Nothing 



