194 THE GRAMMAR OF SCIENCE 



depends not upon its absolute correspondence with any- 

 thing in the real world — a correspondence at once 

 rebutted by the ideal character of geometrical forms — but 

 upon the power it gives us of briefly resuming the facts 

 of perception or of economising thought/ The geometry 

 of motion has been technically termed kijieviatics^ from 

 the Greek word Kiviqixa, signifying a movement. It teaches 

 us how to represent and measure motion in the abstract, 

 without reference to those particular types of motion which 

 a long series of experiments, and much careful observation 

 of the world of phenomena, have shown us are best fitted 

 to exhibit the special changes in the sphere of perception. 

 When we apply what we have learnt in the geometry 

 of motion to those particular types of motion — natural 

 types, as they may be conveniently called — and investi- 

 gate how they are related, then we are led to the 

 so-called Laws of Motion and to those conceptions of Mass 

 and Force'^ upon which our physical description of the 

 universe depends. These will form the topics of succeed- 

 ing chapters, but, in order to see our way more clearly 

 through that maze of metaphysics which at present 

 obstructs the entry to physics, we must devote some space 

 to a discussion of the elementary notions of kinematics. 



1 The term economy of thought, originally due, I think, to Professor Mach 

 of Vienna, embraces in itself a very important series of ideas. Its value is 

 rendered more significant if we remember how thought depends on stored 

 sense- impressions, and that it is difficult to deny to these and to their nexus — 

 association — a physical or kinetic aspect, the iiiipi-ess oi owx terminology (p. 42). 

 The economy of thought thus becomes closely associated with an economy of 

 energy. The range of perceptions is so wide, their sequences so varied and 

 complex, that no single brain could retain a clear picture of the relationship 

 of the smallest group but for the shorthand descriptions provided by the con- 

 ceptions of science. Dr. Wallace, in his Darwhiism, declares that he can 

 find no ground for the existence of pure scientists, especially mathematicians, 

 on the hypothesis of natural selection. If we put aside the fact that great 

 power in theoretical science is correlated with other developments of increasing 

 brain-activity, we may, I think, still account for the existence of pure 

 scientists as Mr. Wallace would himself account for that of worker-bees. 

 Their functions may not fit them individually to survive in the struggle for 

 existence, but they are a source of strength and efficiency to the society which 

 produces them. The solution of Mr. Wallace's difficulty lies, I think, in the 

 social profit to be derived from science as an economy of intellectual energy. 



'■^ Not force as the cause of motion, but force as a measure of motion. 



