DEDUCTION. 125 



portance, , . . the tendency in organic beings 

 descended from the same stock to diverge in 

 character as they become modified." That they 

 have thus diverged was proved by their arrange- 

 ment into groups within groups. "I can re- 

 member," he went on, "the very spot in the 

 road, whilst in my carriage, when to my joy 

 the solution occurred to me; and this was long 

 after I had come to Down." 1 The solution was 

 this, "that the modified offspring of all 

 dominant and increasing forms tend to become 

 adapted to many and highly diversified places 

 in the economy of nature." 



It seems very simple now to understand that 

 the tree-like arrangement of species must be 

 regarded as a direct consequence of the prin- 

 ciple of natural selection. It might even seem 

 easy to infer the tree-like arrangement as a de- 

 duction from the principle, and to discover it, if 

 it had not already been discovered empirically. 

 It is not because Darwin was so slow a thinker 

 that it took him so long to discover the relation 

 of cause and effect between natural selection 

 and the tree-like arrangement of species; but 

 it was because he was a strong and persistent 

 thinker that he discovered it at all. The think- 

 ing out of such connections is always a slow 



1 Life and Letters, Vol. I. pp. 68-70. 



