198 Prof. L. T. More on the 



matter to the role of a mere variation in this otherwise 

 changeless plenum, — making it an attribute rather than an 

 entity. I£ his theory denies the infinite divisibility of 

 matter, it apparently accepts its indefinite divisibility ; the 

 atom, as a variation limited only by our power of observation, 

 must become smaller with each advance in the refinement of 

 our apparatus. Such a plenum must remain a pure creation 

 of the imagination, and its existence is not determinable by 

 physical or experimental methods ; it must therefore be 

 classed as a problem for the metaphysician. The distinction 

 between atoms continually diminishing in size and the 

 infinite, or at least indefinite, divisibility of matter is merely 

 a question of words — the definition of what matter is. 



As another fundamental principle, we shall postulate the 

 objective reality and conservation of matter. The quanti- 

 tative measure of this matter is its mass or inertia, which is 

 also to be taken as an invariable factor in the derived quan- 

 tities, force and energy. M. Hannequin * expresses this 

 idea well when he says : ' w II n'existe done rien, dans le 

 monde mecanique, que des masses en mouvement ou, pour 

 parler un langage rigoureux, qu'une somme constante 

 d'energie de mouvement et des masses sur lesqueles elle se 

 distribute." Although mass is here considered to be infi- 

 nitely divisible, its scientific unit of measurement is at any 

 time, the least amount of which we have cognizance ; at 

 present, this happens to be the electron or corpuscle. 

 Further consideration of this unit is left to the discussion of 

 the atom. 



Few things have been brought out more clearly by the work 

 of the school of energetics than that, if we accept the doctrine 

 of the conservation of energy, either of the two quantities, 

 mass or energy, may be considered as the fundamental unit 

 from which the other can be derived. This undoubtedly 

 follows from the fact that we have no conception of mass 

 without energy or of energy without mass. But while it is 

 thus possible mathematically to make either of them a 

 starting point for the explanation of phenomena, the advo- 

 cates of energetics apparently soon develop a pronounced 

 tendency to prefer the abstract to the concrete and to sub- 

 tilize objective facts into metaphysical ideas. A science 

 like physics, to be useful and not merely an intellectual 

 gymnastics should preserve in all its speculations a close 

 touch with the practical and the concrete, a certain common 

 sense. The history of the science shows these advantages 

 have been obtained most frequently by those who maintain 

 * L'hypoihhe des atonies, p. 127. 



