THE EVOLUTION OF MAN 



deed simple, but so is the solution of the Gordian 

 knot which, according to the legend, was not 

 solved by a clear grasp of the question, but by 

 a blow of the sword. The idea of evolution re- 

 quires that the thing which develops must ex- 

 plain the cause of its development by another 

 thing out of which it developed. There must be 

 as close a relation between these two things as 

 there is between father and son, a deep-seated 

 and intimate likeness combined with an assump- 

 tion of differentiation through progress. Such a 

 relationship and likeness exist between certain 

 chemical and physical qualities and parts of the 

 living amoeba, and such simple chemical combin- 

 ations of so-called inorganic substances, as water, 

 air and the like. But there is no such likeness 

 in regard to the most characteristic mark of an 

 amoeba, that is to say, subjective feeling, which 

 is completely missing in purely chemical reac- 

 tions. Here, we have the old and always relia- 

 ble philosophical axiom that "sensation" cannot 

 be derived from mere "motion." It is true that 

 the field of sensation likewise is strictly under the 

 control of the law of causation and does not ad- 

 mit of any "miracles." But, for this very reason 

 it is never possible to derive a process of sensa- 

 tion from so totally different a thing as a process 



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