286 THE GRAMMAR OF SCIENCE 



If the reader once grasps that every corpuscle in the 

 universe must be conceived as influencing the motion of 

 every other corpuscle, he will then fully appreciate the 

 complexity of the corpuscular dance by aid of which we 

 symbolise the world of sense -impressions. The law of 

 motion just stated probably applies to prime-atoms, and 

 through them to chemical atoms, molecules, and particles. 

 Possibly it does not apply to distant ether-elements 

 directly, but these, perhaps, influence each other's motion 

 only indirectly by directly influencing the motion of their 

 immediate neighbours. In this case the " action at a 

 distance " generally asserted of corpuscles of gross 

 " matter " may very probably be conceived as due to the 

 action between adjacent ether-elements. We should then 

 have to state the first law as follows : — 



Every corpuscle, zvhether of ether or gross " mattcrl^ 

 influences iJie motion of the adjacent ether corpuscles, and 

 tJirough them of every other corpuscle, however distant ; the 

 influence thus spread is nevertheless very insignificant at 

 great as compared zvith small distances. 



S 4. — The Second Law of Motion, or the Principle of Inertia 



Now, in constructing the universe conceptually from 

 our corpuscles, it is impossible to take into account the 

 influence of all the corpuscles upon each other at one and 

 the same time. Accordingly we neglect at once influences 

 which even in the aggregate are beyond our powers of 

 measurement. Further, we purposely exclude from con- 

 sideration slight, if measurable, variations of motion due 

 to more distant groups. We isolate a particular group of 

 corpuscles, and this group which we deal with conceptually 

 apart from the rest we term, for the purposes of some 

 particular discussion, the f eld. 



The most limited field that we can conceive is that of 

 a single corpuscle. If we could isolate such a corpuscle 

 from the rest of the conceptual universe, how would it 

 move ? At first sight the question is absurd, because in 

 Chapter VI. (p. 206) we saw that motion is meaningless 



