MATTER 259 



by which we briefly describe the sequences and relation- 

 ships we perceive between various groups of phenomena. 

 The ether is thus a mode of resuming our perceptual 

 experience ; but, like a good many other conceptions of 

 which we have no direct perception, physicists project 

 it into the phenomenal world and assert its real existence. 

 There seems to be just as much, or little, logic in this 

 assertion as in the postulate that there is a real substratum, 

 matter, at the back of groups of sense-impressions ; both 

 at present are metaphysical statements. Now there is no 

 evidence forthcoming that the ether must be conceived as 

 either hard or heavy ,^ and yet it can be strained or its 

 parts put in relative motion. Further, from Professor 

 Tait's standpoint, it occupies space. Hence those who 

 associate matter with hardness and weight must be pre- 

 pared to deny that the ether is matter, or be content to 

 call it non-matter. It is worth noting, at the same time, 

 that the metaphysicians — whether they be materialists 

 asserting the phenomenal existence both of space and of 

 a permanent substratum of sense-impression, or " common- 

 sense " philosophers asking us to knock our heads against 

 stone walls — reach hopelessly divergent results when they 

 say that matter is that which moves, that matter occupies 

 space, and that matter is that which is heavy and hard. 



8 8. — Matter as no7i-Matter in Motion 



There is, however, a still greater dilemma in store for 

 the " common-sense " philosophers. We have not yet 

 reached a clear conception of what the ether, the non- 

 matter of our philosophers, consists in. There are in fact 

 two, at first sight, completely divergent ways in which the 

 ether is reached as a conceptual limit to our perceptual 

 experience (see p. 181), but it is the great hope of science 

 at the present day that " hard and heavy matter " will be 



1 I venture to think Sir William Thomson's attempt to weigh ether a 

 retrograde step (see his Lectures on Molectilar Dynamics, pp. 206-8, 

 Baltimore, 18S4). If the ether be a sufficiently wide-embracing conception, 

 gravitation should flow from it, and this certainly was Sir William's view when 

 he propounded the vortex atom. 



