70 THE FITNESS OF THE ENVIRONMENT 



that there are not an infinity of important 

 physical properties ; in fact there are very 

 few. And in the second place it is evident, 

 both from centuries of experience in physical 

 science and from the postulates above adopted 

 regarding life, which undoubtedly do in the 

 main describe its physico-chemical character- 

 istics, that very few properties indeed are of 

 importance in the least comparable with those 

 which I have mentioned. 



Finally, it is in the highest degree probable 

 that we are acquainted with most of the truly 

 essential physical properties, and know them as 

 biologically important, when they are so ; and I 

 think we shall find it possible to consider them 

 all, and thus to make the argument complete. 



Meanwhile it should be noted that there are 

 two different ways of illustrating the fitness 

 of a physical property. Properly employed, 

 both are free from fallacy, and it will be de- 

 sirable for us to employ both. Thus it may 

 be shown, as in the case of the temperature of 

 the ocean, that a particular property of water, 

 its high specific heat, automatically produces 

 a maximum of something which is favorable 

 to life. Or again, as in the case of the regula- 

 tion of the temperature of the human body by 

 the process of perspiration, it may be shown 

 that a particular property of water, its high 



