THE ARGUMENT 267 



unique, as those which have been considered 

 and set forth. 



With the assurance that, in such measure 

 as the present state of science permits, our 

 study has been indeed exhaustive, a final 

 argument arises. So far as we can see, all the 

 properties of water, carbonic acid, and the 

 three elements are fit, according to our defi- 

 nition of fitness. There is nothing about these 

 substances that is really and seriously inferior 

 to the same thing in any other substance; 

 and in all the subjects which we have reviewed 

 not a single disability of the primary constit- 

 uents of the environment has come to light. 



in 



SUMMARY 



For the convenience of my readers the argu- 

 ment which has been developed in the course 

 of the preceding pages is here re-stated in 

 outline. 



I. Fitness is a mutual or reciprocal 

 relationship between the organ- 

 ism and the environment. 



II. Life is a mechanism (from the 

 point of view of physical sci- 

 ence) . Accordingly it must be — 



