74 ESSAYS OF A BIOLOGIST 



all phenomena. It is merely that we have not yet 

 found a method for the direct detection of mental 

 processes as we have, say, for electrical processes; 

 but something of the same general nature, the same 

 category as mind must, if we wish to preserve our 

 scientific sanity, our belief in the orderliness of the 

 world, be present in lower organisms and in the life- 

 less matter from which they originally sprang. 



In the present state of our knowledge, the study 

 of physics and chemistry can be pursued without 

 any reference to mental processes. But the study 

 of biology cannot: and that is one reason why the 

 centre of gravity of science as a whole is shifting — 

 it is shifting for exactly the same reason that the 

 centre of gravity of a house shifts during its con- 

 struction — because the foundations have to be built 

 first. 



Our second reason is as follows. Biology is once 

 more the link between root and flower, between 

 physics and chemistry and human affairs, in regard 

 to evolution. I say evolution : it would be better to 

 broaden the idea by saying the directional processes 

 to be seen in the universe. So far as a main direc- 

 tion is to be observed in physics and chemistry, it is, 

 as all authorities are agreed, towards the degradation 

 of energy and a final state in which not only life but 

 all activity whatsoever will be reduced to nothing, 

 all the waters of energy run down into a single dead 

 level of moveless ocean. Biology, on the other 

 hand, presents us with the spectacle of an evolution 



