PT. n. Mr. Darwin and Mr. Buckle. 93 



the whole of that wonderful machinery by which 

 living beings, from their lowest to their highest forms, 

 have been produced in all their marvellous combi- 

 nations follow from his motive power of Natural 

 Selection and Sexual Selectibn alone. But it is for 

 him to prove his system. The first and obvious 

 character imprinted upon the whole is that of in- 

 vention, emanating from a superior Power, a superior 

 Intelligence, and a superior Will. 



I have remarked in a previous part of this Essay 

 that all our progress in knowledge and in Science is 

 attained by three methods : the first by the appli- 

 cation of the exact sciences to the determination of 

 all those questions to which they can be applied ; the 

 second, the evidence of fact ; and the third, experi- 

 ment employed to elicit fact. Now the first step in 

 Mr. Darwin's theory may be regarded as founded 

 upon the first of these methods ; the ratio of increase 

 in living- beings is an arithmetical problem which 

 follows from the premises. But his second propo- 

 sition that all the countless varieties of organised 

 Life upon this globe are derived from the action of 

 two principles, that of Natural Selection and of 

 Sexual Selection, is a proposition which cannot be 

 mathematically demonstrated, and which must be 



