VI. 



ARE PHYSICAL, BIOLOGICAL, AND PSYCHO- 

 LOGICAL CATEGORIES IRREDUCIBLE ? 1 



The subject of this discussion, as I understand it, is 

 whether the general conceptions or " categories " ordi- 

 narily used in interpreting physical, biological, and 

 psychological phenomena are essentially different and 

 irreconcilable with one another. 



In approaching this question I think we must care- 

 fully distinguish between the conceptions, or, as I should 

 prefer to say, working hypotheses, which we commonly 

 use in interpreting reality, and that reality itself. The 

 discussion applies to our working hypotheses or cate- 

 gories ; and I propose to maintain that our ordinary 

 working conceptions of what we regard as physical, 

 biological, and psychological phenomena are not only 

 different, but irreducible to one another. 



I will deal first with the difference between physical 

 and biological interpretations of experience. The theory 

 which aims at interpreting the phenomena of life as 

 nothing but physical and chemical phenomena, accom- 

 panied, it may be, by consciousness, is generally known 

 as the mechanistic theory of life. The theory which, 



1 Opening paper of a symposium, Aristotelian Society, July 6, 

 1918. 



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