in A MENTAL WORK 143 



supply of oxygen, and for its absorption, 

 some nervous system for the genera- 

 tion of the highest energies of life, 

 some optical arrangement for the pur- 

 poses of sight all of these, and many 

 more, involve, of necessity, likenesses 

 and correspondences between all living 

 things in the animal kingdom. These 

 correspondences hang together by a 

 purely mental and rational chain of 

 common necessities which have been 

 seen and have been accordingly provided 

 for. These mental relations between 

 needs and their supply are entirely in- 

 dependent of the methods employed, 

 and, as a fact, the methods employed do 

 very considerably vary. The argument 

 would be exactly the same if the methods 

 of supply were much more various than 

 they actually are. If the one method 

 employed has never been anything but 

 ordinary generation, with the single 



