THE UNITY OF NATURE. 269 



digestion, assimilation, and circulation. Only two 

 branches of the life of the organism, mental action 

 and reproduction, retained any element of mystery, 

 and seemed inexplicable without assuming a vital 

 force. But immediately after Miiller's death such 

 important discoveries and advances were made in 

 these two branches that the uneasy " phantom of 

 vital force " was driven from its last refuge. By 

 a very remarkable coincidence Johannes Muller 

 died in the year 1858, which saw the publication 

 of Darwin's first communication concerning his 

 famous theory. The theory of selection solved the 

 great problem that had mastered Muller — the question 

 of the origin of orderly arrangements from purely 

 mechanical causes. 



Darwin, as we have often said, had a twofold 

 immortal merit in the field of philosophy — firstly, 

 the reform of Lamarck's theory of descent, and its 

 establishment on the mass of facts accumulated in 

 the course of the half- century ; secondly, the con- 

 ception of the theory of selection, which first revealed 

 to us the true causes of the gradual formation of 

 species. Darwin was the first to point out that the 

 " struggle for life " is the unconscious regulator which 

 controls the reciprocal action of heredity and adapta- 

 tion in the gradual transformation of species ; it is 

 the great " selective divinity " which, by a purely 

 " natural choice," without preconceived design, creates 

 new forms, just as selective man creates new types by 

 an ''artificial choice" with a definite design. That 

 gave us the solution of the great philosophic problem : 

 " How can purposive contrivances be produced by 

 purely mechanical processes without design ?" Kant 

 held the problem to be insoluble, although Empedocles 



