312 THE GRAMMAR OF SCIENCE 



result from the nature we postulate for the ether and 

 from the particular types of ether-motion by aid of which 

 we construct the various phases of gross " matter." 



It is not, therefore, questioning the well-established 

 results of modern physics when we ask whether to con- 

 ceive the ether as a pure mechanism ^ is, after all, scientific. 

 The object of science is to describe in the fewest words 

 the widest range of phenomena, and it is quite possible 

 that a conception of the ether may one day be formed 

 in which the mechanism of gross " matter " itself may, to 

 a great extent, be resumed. Indeed, it is on these points 

 of the constitution of the ether and the structure of the 

 prime-atom that physical theory is at present chiefly at 

 fault. There is plenty of opportunity for careful experi- 

 ments to define more narrowly the perceptual facts we 

 want to describe scientifically ; but there is still more 

 need for a brilliant use of the scientific imagination 

 (p. 30). There are greater conceptions yet to be formed 

 than the law of gravitation or the evolution of species by 

 natural selection. It is not problems that are wanting, 

 but the inspiration to solve them ; and those who shall 

 unravel them will stand the compeers of Newton, Laplace, 

 and Darwin. 



§ I 2. — Density as the Basis of the Kinetic Scale 



If our mechanism as it is formulated in the above 

 laws of motion can only be definitely asserted as true for 

 particles, we have still to ask how the geometrical forms 

 by which we symbolise perceptual bodies are to be con- 

 ceived as constructed from particles, and how many 

 different families of particles we are to postulate. Now 

 in order to appreciate the answer to this question, we 

 must define what we mean by sameness of substance. 

 Suppose we take two portions of different bodies, or of the 



1 By a pure mechanism the writer means the reader to understand a 

 system which is conceived to obey all the fundamental laws of motion as 

 stated in mechanical treatises. 



