ABSOLUTE IDEALISM 89 



exposition of the theory by Laplace simply confirmed its hold. 

 Closely bound up, again, with spatial relativity is the relativity 

 of temporal position and magnitude; for time is habitually treated 

 by the scientist as a sort of one-dimensional space. When this 

 also has been embraced, there remains no convincing reason for 

 questioning the similar nature of the mechanical concepts of 

 mass and force. The general doctrine, then, of the relativity 

 of all the primary qualities of matter becomes so far from para- 

 doxical, that it is apt to meet with unquestioning acceptance. 



But the primary qualities of matter are precisely those upon 

 which rationalism had fixed as constituting its essence. The 

 relativity of the secondary qualities had been recognized by Des- 

 cartes, and it was for this reason that he branded them as mere 

 appearance. Precisely the same conclusion was therefore natural 

 in the case of the primary qualities. Leibniz actually reached 

 this conclusion with respect to extension ; and only the then cha- 

 otic state of elementary mechanics permitted him to avoid equally 

 condemning motion and energy. When therefore, the mechan- 

 ical theory of the eighteenth century had assumed its classi- 

 cal form, the time was ripe for the announcement of the thesis, 

 that all the knowable qualities of material things are determined 

 by their relations to other things, and hence are merely phe- 

 nomenal. 



This conclusion was facilitated by another consideration, 

 which, however, for the rationalists was not clearly distinct from 

 the foregoing. The observable qualities of things are not 

 only relative in the sense of owing their meaning to their implied 

 reference to the qualitites of other things. They are also (with 

 the exception of mass 1 ) relative in the sense that they change in 



^Ve are not surprised to find a disposition to identify the concept of mass with 

 that of matter itself. Size and shape, density and velocity are then recognized as 

 accidents: but the material body not only has mass, but is the mass. Otherwise 

 put, mass shows an evident tendency to replace extension as the essence of matter. 

 But aside from the fact that its 'mathematical' relativity is a fatal obstacle to a 

 strictly rationalistic interpretation, there is a further difficulty yet to be men- 

 tioned. It is readily perceived that the concept of mass has meaning for us only 

 in connection with those of duration, extension, and force> Mass may, indeed, 



