CHAPTER III 



Of all young creatures, the human infant is the most 

 helpless, the least equipped Avith instinct for the hattle 

 of life ; of all grown creatures the adult man is the most 

 helpful, the best equipped with reason for the strife. 

 Beyond all other creatures, the human being possesses 

 the power of mentally varying in response to stimula- 

 tion from the environment, and thereby bringing him- 

 self into completer harmony with it. And always, owing 

 to the imitative instinct, as strong in him as in lower 

 animals, his variations tend to reproduce those of his 

 immediate predecessors. At birth his mind, mainly the 

 product of that great mass of nerve tissue, the cerebrum, 

 is an unploughed field, which, ploughed by experience, 

 brings forth, according to the seed that is sown ; a blank 

 unwritten page on which chance shall write ; a mass of 

 clay ductile to the hands of the moulder. 



If we bear steadily in view the two cardinal facts, (1) 

 that the mind of man is compounded almost entirely of 

 acquired traits, — acquired knowledge, acquired ways of 

 thinking and acting, acquired likes and dislikes, &c. ; and 

 (2) that the action of Natural Selection has plainly been 

 such as to cause in him, not an evolution of this or that 

 mental trait, but mainly of a power of acquiring mental 

 traits in response to stimulation, we are able to under- 

 stand many things which at first sight seem puzzling. 



165 



