FITNESS 19 



of the foundation of thermodynamics. 1 To- 

 day we know that just so much heat, neither 

 more nor less, may be obtained by the com- 

 plete conversion of a unit of electrical energy 

 or by a given chemical process. We know, 

 moreover, that not every conceivable change 

 from one form of energy to another is possible. 

 On the whole, energy can flow in but one 

 direction; perpetual motion is impossible; 

 and useful energy is steadily becoming de- 

 graded, dissipated, and useless. 



Such laws are fully worthy of a place be- 

 side the periodic law, and they justify equal 

 confidence in the adequacy of our current 

 descriptions of matter and of energy for the 

 purposes of biology. 



C 



SPACE AND TIME 



Since Kant revolutionized modern phi- 

 losophy, the whole world has steadily realized 

 that between matter and energy on the one 

 hand, and space and time on the other, there 

 is a real and highly significant difference. 2 



1 An excellent account of this period may be found in 

 Merz's "History of European Thought in the Nineteenth 

 Century," Vol. II, Chap. VII, "On the Physical View of 

 Nature." 



2 For a brief statement of Kant's argument see Royce, 

 "The Spirit of Modern Philosophy," pp. 121-125. 



