66 The Evolution Hypothesis. 



such a formula be discoverable evolution cannot be 

 raised to the dignity of an all-embracing hypothesis, 

 or successfully maintained as a sufficient explanation 

 of any individual thing. It has, in that case, no 

 claim to rank as a cosmic philosophy. 



A unifying principle is indispensable, if evolution is 

 to be accepted as a rational theory. Under that prin- 

 ciple every knowable law must be subsumed. There 

 may not be any law discoverable in any department 

 of thought that cannot be brought under it, as the 

 lower under the higher generalization. 



The weight of Socrates was determined by the 

 dynamic law of gravity, and when his disciples 

 covered his face after death his body was still subject 

 to that law ; but governing his action while alive 

 were other laws laws of the true Socrates. If among 

 these there were any the laws of thought and con- 

 science, for example not reducible to unity with the 

 physical universe, it would be but trifling with the 

 question to affirm that knowledge is unified, simply 

 because the body of Socrates is known to have been 

 included under physical law while the real Socrates, 

 who passed out of reach of his disciples, is left out 

 of account. The principle that is to unify all 

 knowledge must account for all the known phases, 

 of all known phenomena, and especially those charac- 

 teristics by which they are differenced. It is not 

 enough that it should deal with a part of concrete 

 being, it must deal with all concrete being : it must 



