76 BIOLOGY AND PHYSICAL SCIENCES 



for organic life, as the idea of life is 

 one of the fundamental ideas. There is 

 no reason why a category or general 

 conception of life should not be just 

 as much constitutive of our experience as 

 the category of substance. Here, there 

 fore, we have a possible way out of our 

 difficulties with the mechanistic theory of 

 life. In trying to reduce life to physical 

 and chemical mechanism we are perhaps 

 in some way confusing two different cate 

 gories. Kant's general philosophical con 

 clusions have in any case thrown a quite 

 new light on our conceptions of the physical 

 world, and have taught us that the validity of 

 these conceptions is of a very different nature 

 from what was previously believed. It may 

 be that just as we cannot base physics on the 

 purely mathematical conceptions of exten 

 sion, so we cannot base biology on the 

 purely physical conceptions of matter and 

 energy. With these possibilities in mind let 

 us return to a discussion of the facts which 

 biological investigation discloses. 



What we have first to ask is whether, as a 

 matter of fact, we habitually use, in dealing 



