EVOLUTION THE MASTER-KEY 



it may be maintained that even a speculative 

 opinion on this matter may well affect conduct in 

 that it can scarcely fail to affect one's intellectual 

 and emotional attitude towards life. 



Let us note, then, in the first place, that the 

 Pythagorean idea of exact recurrence, or, indeed, 

 the idea of anything like exact recurrence, is in- 

 compatible with the modern scientific belief that 

 causation is universal. This belief, if it be true, 

 implies that every act, however small, whether per- 

 formed on the house-tops or in solitude, affects, 

 in its measure, the whole subsequent course of 

 events of all events, since 



"thou canst not stir a flower 

 Without troubling of a star" 



a statement which Newton has taught us to be 

 literally true. 



In the second place, there is the fact, which 

 cannot be discounted by the Aristotelian specula- 

 tion quoted above, that human knowledge is now 

 capable of influencing external events in a measure, 

 which, amazing though it would have seemed to 

 our great-grandfathers, promises future develop- 

 ments to which we can set no measure whatever. 

 The agnostic assertion as to our knowledge of 

 reality, which is implied in the term unknowable, 

 and which is deduced from the considerations of 

 psychology, is entirely compatible with the belief 

 that there is no necessary limit whatever to 



