CHAPTER III 

 THE UNDERLYING IDEA 



WE have seen in the preceding chapters how the 

 idea of evolution worked its way through the minds 

 of men. Man after man got a glimpse of the idea, 

 even among the ancient philosophers. But no one 

 could speak convincingly on the subject before modern 

 times, when a wider acquaintance with the animal 

 world gave a body of facts on which it was safe to 

 base conclusions. Even then the idea eluded men, 

 until there came a worker trained by a long voyage 

 around the world in which he had nothing to do ex- 

 cept to study nature. He finally gathered in his mind 

 material sufficient to convince himself not only of the 

 truth of evolution but of the process by which this 

 evolution was brought about. Every scientific prin- 

 ciple is simple in its basal idea. In actual life the 

 action of the principle may be so bound up with 

 others as to need a skillful mind for its detection. But 

 under all the complexities and modifications, like a 

 silver thread woven into a cloth, runs the basal idea. 

 Until a master has detected it the presence of it may 

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