370 



FOOT-NOTES TO EVOLUTION. 



the intense practicality of the senses and the intellect. 

 They tell us the truth as to external things, in so far as 

 this truth has been essential to our ancestors. Those of 

 our predecessors who did not " see things 

 rac ica 1 y o ^^ they really are," to the degree that 

 the senses. , . ,.\. , , , , 



their life processes demanded, have died, 



leaving no descendants. Our own ancestors, through 

 all the generations, have been creatures of adequate sen- 

 sations and of adequate power of thought. Were it not 

 so, they would have been unable to cope with their en- 

 vironment. In other words, the sensations their brains 

 translated into action were truthful enough to make ac- 

 tion safe. That our ordinary sensations and our induc- 

 tions from them are truthful so far as they go, is proved 

 by the fact that we have safely trusted them. This is 

 shown also by the instruments of precision which are 

 the tools of science. That instruments of precision like- 

 wise tell the truth, is shown by the fact that we can 

 trust our lives to them. That they are more trust- 

 worthy than the unaided senses, is shown by their greater 

 safety. 



But while our senses tell the truth as to familiar 

 things, as rocks and trees, foods and shelter, friends and 

 enemies, they do not tell the whole truth. They go 

 only as far as the demands of the environment have 

 compelled them to go. Chemical composition they do 

 not show. Objects too small to be handled are too 

 small to be seen. Bodies too distant to be reached are 

 never correctly apprehended. Accuracy of sense grows 

 less as the square of the distance increases ; and sun 

 and stars, clouds and sky, are in fact very different from 

 what they seem. 



In matters not vital to action exact knowledge loses 

 its importance. It is perfectly safe, in the ordinary 

 affairs of life, to believe in witches and incantations, 



