EVOLUTION THE MASTER-KEY 



was that of a railway engineer. These facts are 

 worth remembrance in their bearing on Spencer's 

 status as a psychologist. He made contributions 

 to every branch of science, and laid all under 

 contribution for his philosophic system ; but he cer- 

 tainly followed the advice to know a little of every- 

 thing and everything of something, for in psy- 

 chology he was not only a pioneer by reason of one 

 great idea, but was also a specialist a master 

 alike of principles and details, to quote the au- 

 thoritative obituary notice in Nature. 



Yet though Locke's immortal essay lay upon his 

 father's shelves, Spencer did not acquire enough 

 interest in the science of mind even to impel him 

 to the opening of any work that dealt with it until 

 his meeting with Lewes, in his thirty-first year, 

 led him to read that Biographical History of Philos- 

 ophy which has opened a door into a new world 

 for so many of us before even emerging from our 

 teens. 



But when at length Spencer did awake to the 

 fascinations of psychology, he forthright proceeded, 

 with the audacity of genius, to plan a book of at 

 least two volumes which was to deal with the 

 whole subject. We need not wonder that the 

 project languished until there came to him a 

 simple but important idea which was capable of 

 comparatively brief treatment, and gave him the 

 needed start. He began to write the Principles 

 of Psychology when he was thirty-four, three years 

 after his introduction to the subject through a 

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