1 1 6 The Evolution Hypothesis. 



tion. We reach a line of limit, on the one side of it 

 is force, on the other nothing : that line divides 

 being from not-being. But Mr. Spencer has been at 

 great pains to show that no such mental process is 

 possible ; that non-existence cannot be presented in 

 thought. Taking his own criterion as the test of 

 truth, this conception must be rejected. 



One other criticism may be added. The unification 

 of knowledge is the answer of philosophy to the 

 craving for unity of thought. That evolution seems 

 to explain nature so as to let the mind pass con- 

 tinuously onward without break in the connection of 

 fact with fact, is a chief source of its hold on men of 

 science. In view of this habit of scientific thinking, 

 it is curious to see how the very first step in the pro- 

 cess is a breach of continuity. If the universe be 

 infinite, continuity is broken by every line that marks 

 heterogeneity : if the universe be finite, the mind 

 must fix a circumscribing limit ; when thought reaches 

 that line, it is sharply arrested by a boundary beyond 

 which nothing exists. Now, if the law of continuity 

 must be broken when we come to the " walls of the 

 world ; " if evolution lays down limiting, or differenc- 

 ing, lines as essential to its initial process in inter- 

 preting the universe, it is manifest that breach of 

 continuity lies at the root of all mental activity, that 

 it is an essential necessity of thought, and " to know 

 in part " is the normal condition of intelligence. 



One other mode of conceiving the primal form of 



