218 THE RIDDLE OF THE UNIVERSE. 



strenuous opposition from the vitalistic biologists and 

 the dualist and spiritualist philosophers. For these 

 the peculiar " spiritual forces " of human nature are 

 a group of "free" forces, not subject to the law of 

 energy ; the idea is closely connected with the dogma 

 of the " freedom of the will." We have, however, 

 already seen (p. 208) that the dogma is untenable. 

 Modern physics draws a distinction between " force " 

 and "energy," but our general observations so far 

 have not needed a reference to it. 



The conviction that these two great cosmic theorems, 

 the chemical law of the persistence of matter and the 

 physical law of the persistence of force, are funda- 

 mentally one, is of the utmost importance in our 

 monistic system. The two theories are just as 

 intimately united as their objects — matter and force 

 or energy. Indeed, this fundamental unity of the 

 two laws is self-evident to many monistic scientists 

 and philosophers, since they merely relate to two 

 different aspects of one and the same object, the 

 cosmos. But, however natural the thought may be, 

 it is still very far from being generally accepted. It 

 is stoutly contested by the entire dualistic philosophy, 

 vitalistic biology, and parallelistic psychology ; even, 

 in fact, by a few (inconsistent) monists, who think 

 they find a check to it in " consciousness," in the 

 higher mental activity of man, or in other phenomena 

 of our " free mental life." 



For my part, I am convinced of the profound 

 importance of the unifying " law of substance," as 

 an expression of the inseparable connection in reality 

 of two laws which are only separated in conception. 

 That they were not originally taken together and their 

 unity recognised from the beginning is merely an 



