274 THE GRAMMAR OF SCIENCE 



it can throw absolutely no light on the reason why- 

 material particles move. " Force is a direct object of 

 sense," write Sir William Thomson and Professor Tait.-^ 

 Force " is not a term for anything objective," writes 

 Professor Tait.^ In the face of such contradictions, is it 

 not better to cease supposing that any lucid explanation 

 of the why of motion can be abstracted from the idea of 

 force ? 



But may not our particles, like two dancers, hold 

 hands, and so the one " enforce " the other's motion ? 

 We must not say that this holding hands is impossible, 

 although the particles be 90,000,000 miles apart. We 

 conceive light as easily traversing those 90,000,000 miles 

 by aid of the ether, and may not our particles hold hands 

 by means of the ether ? All scientists hope that this may 

 be so, at any rate conceptually, although they have not 

 yet conceived how it can be so. But if we phenomen- 

 alised the ether and were able to describe by aid of it 

 action at a distance of millions of miles, we should still 

 be left with the problem : Why does the relative position 

 of two adjacent parts of ether influence the motion of 

 those parts ? It might seem at first sight easier to 

 explain why two adjacent ether elements " move each 

 other " than why two distant particles of matter do. The 

 common-sense philosopher is ready at once with an 

 explanation : They pull or push each other. But what do 

 we mean by these words ? A tendency when a body is 

 strained to resume its original form ; a tendency in a 

 certain relative position of its parts to a certain relative 

 motion of its parts. But why does this motion follow on 

 a particular position ? It is the old problem over again, 

 with the difference that relative position now involves 

 small instead of large distances. It will not do to 

 attribute it to the elasticity of the medium ; this is merely 

 giving the fact a name. We do indeed try to describe 

 the phenomenon of elasticity conceptually, but this is 

 solely by constructing elastic bodies out of non-adjacent 



1 A Treatise on Natural Philosophy, part i. p. 220. Cambridge, 1879. 

 2 The Properties of Matter. Edinburgh, 1885. 



