v.] IN THE THEORY OF NATURAL SELECTION. 303 



necessary to seek the aid of some general theory for the 

 arrangement and grouping of those which we already possess. 

 This has been my object in the present paper. 



But it may be perhaps objected that these phenomena are 

 far too complicated to be attacked at the present time, and that 

 we ought to wait quietly until the simpler phenomena have 

 been resolved into their components. It may be asked whether 

 the trouble and labour involved in the attempt to solve such 

 questions as heredity or the transformation of species are not 

 likely to be wasted and useless. 



It is true that we sometimes meet with such opinions, but 

 I believe that they are based upon a misunderstanding of the 

 method which mankind has always followed in the investiga- 

 tion of nature, and which must therefore be founded upon the 

 necessary relations existing between mankind and nature. 



Science has often been compared to an edifice which has 

 been solidly built by laying stone upon stone, until it has 

 gradually risen to greater height and perfection. This com- 

 parison holds good up to a certain point, but it leads us to 

 easily overlook the fact that this metaphorical building does not 

 at any point rest upon the ground, and that, at least up to the 

 present time, it has remained floating in the air. Not a single 

 branch of science, not even Physics itself, has commenced 

 building from below ; all branches have begun to build at 

 greater or less heights in the air, and have then built down- 

 wards : and even Physics has not yet reached the ground, for 

 it is still very uncertain as to the nature of matter and force. 

 In no single group of phenomena can we begin with the in- 

 vestigation of ultimate causes, because at this very point our 

 means of reasoning stop short. We cannot begin with ultimate 

 phenomena and gradually lead up to those which are more 

 complicated : we cannot proceed synthetically and deductively, 

 building up the phenomena from below ; but we must as a rule 

 proceed analytically and inductively, proceeding from above 

 downwards. 



No one will dispute these statements, but they are often for- 

 gotten, as is proved by the above-mentioned objection. If we 

 were only permitted to attack the more complicated phenomena 

 after gaining a complete insight into the simpler ones, then all 

 scientists would be physicists and chemists, and not until 



