Scope and Purport of Evolution 49 



the special interpretations of reflex action, instinct, 

 memory, reason, emotion, and will are such as to 

 make the " Principles of Psychology " indubitably 

 the most suggestive book upon mental phenomena 

 that was ever written. 



Toward the end of the first edition of the " Origin 

 of Species," published in 1859, Mr. Darwin looked 

 forward to a distant future when the conception of 

 gradual development might be applied to the phe- 

 nomena of intelligence. But the first edition of 

 the " Principles of Psychology," in which this was so 

 successfully done, had already been published four 

 years before, in 1855, so that Mr. Darwin in 

 later editions was obliged to modify his statement, 

 and confess that, instead of looking so far forward, 

 he had better have looked about him. I remem- 

 ber hearing Mr. Darwin laugh merrily over this at 

 his own expense. 



This extension of the doctrine of evolution to 

 psychical phenomena was what made it a universal 

 doctrine, an account of the way in which the world, 

 as we know it, has been evolved. There is no sub- 

 ject, great or small, that has not come to be af- 

 fected by the doctrine, and, whether men realize it 

 or not, there is no nook or corner in speculative 

 science where they can get away from the sweep 

 of Mr. Spencer's thought. 



