178 THE GRAMMAR OF SCIENCE 



it, but we cannot in the least predict how they would be 

 related to a world which is at present beyond perception. 



§ 10. — Conceptual Contimtity. Ether 



The reader will now be prepared to appreciate scien- 

 tific conceptions, which, if they corresponded to realities 

 of the phenomenal world, would contradict each other. 

 Having destroyed the continuity of bodies by the idea of 

 atom, it might at first sight appear as if our conceptual 

 space were fundamentally different from perceptual space. 

 The latter, as we have seen, is our mode of distinguishing 

 groups of sense-impressions, and where there is nothing 

 to distinguish, there there is no space. The perceptive 

 faculty rather than nature may be said " to abhor a 

 vacuum." On the other hand, having destroyed the con- 

 tinuity of bodies by the atomic hypothesis, we seem at 

 first sight to be postulating a void in conceptual space. 

 But here the physicist compels us to introduce a new 

 continuity. This new continuity is that of the ether, a 

 medium which physicists conceive to fill up the interstices 

 between bodies and between the atoms of bodies. By 

 aid of this concept, the ether (to which we shall return 

 later), we are able to classify and resume other wide 

 groups of sense-impressions. With regard to the per- 

 ceptual existence of the ether, it now stands, some physi- 

 cists would assert, on a rather different footing from that 

 of the atom. By the real existence of anything we mean 

 (p. 70) that it forms a more or less permanent group of 

 sense-impressions. Now this can hardly be asserted of 

 the ether ; we conceive it rather as a conduit for the 

 motions by which we interpret sense-impression. The 

 nerves seem to us conduits of the like kind, but then the 

 nerves also appear to us as permanent groups of sense- 

 impressions apart from their function of conductivity. 

 There are no sense-impressions which we class together 

 and term ether, and on this account it still seems better 

 to consider the ether as a conception rather than a per- 

 ception. It is true that to some minds the ether may 



