IDEAS OF PHYSICAL CHEMISTRY 11 



that we can ascribe all the phenomena which we see to the 

 combination of these essential principles, of whose nature 

 we know nothing, and which are, consequently, infinite to us. 

 This does not preclude our singling out finite portions of 

 these, so to speak, and defining them by each other. 



We have seen that we are not justified in calling substance 

 a manifestation of matter free of energy: it is so intimately 

 connected with certain forces (such as gravitation) which are 

 convertible into so-called manifestations of pure energy, 

 that we cannot conceive of it as existing deprived of these, 

 and yet remaining recognizable. But we may neverthe- 

 less class all substances together in one general class called 

 matter. 



Thus also, the various modes of energy heat, motion, 

 electricity, chemical affinity are phenomena which we 

 dare not ascribe to energy alone, for we cannot conceive them 

 as separated from matter. We can, therefore, speak of their 

 differentiation also, although we may picture the tran- 

 scendental energy as one and homogeneous. Indeed, con- 

 sciously or unconsciously, this distinction is made in the 

 science of thermodynamics, which proposes to treat energy 

 in its abstractest form. . . . 



In view of these philosophical complications, I propose 

 that we do not allow ourselves to be hampered by metaphys- 

 ical notions as to the respective homogeneity of matter and 

 energy, but that we accept frankly, at the outset, the appear- 

 ance of substances and forces in various distinct forms. 

 Physical research will show us that there exist between all 

 these forms certain relations, about which it is our duty to 

 procure definite ideas. If the advance of knowledge shall 

 gratify our love of symmetry, by proving that the correla- 

 tions of the various forms may be traced to the existence of a 

 simpler set of relations, of a higher order, well and good ! But 



