CHAPTER VII 



MATTER 



§ I. — " All things move " — but only in Conception 



An old Greek philosopher, who lived perhaps some five 

 hundred years B.C., chose as the dictum in which he 

 summed up his teaching the phrase: ^^ All tilings flow y 

 After-ages, not understanding what Heraclitus meant — it 

 is doubtful whether he understood himself — dubbed him 

 " Heraclitus the Obscure." But to-day we find modern 

 science almost repeating Heraclitus' dictum when it says : 

 " All tilings are in motion" Like all dicta which briefly 

 resume wide truths, this dictum of modern science re- 

 quires expanding and explaining if it is not to be misin- 

 terpreted. By the words " All things are in motion " we 

 are to understand that, step by step, science has found it 

 possible to describe our experience of perceptual changes 

 by types of relative motion : this motion being that of 

 the ideal points, the ideal rigid bodies, or the ideal strain- 

 able media which stand for us as the signs or symbols 

 of the real world of sense-impressions. We interpret, 

 describe, and resume the sequences of this real world of 

 sense- impressions by discussing the relative positions, 

 velocities, accelerations, rotations, spins, and strains of an 

 ideal geometrical world which stands for us as a concep- 

 tual representation of the perceptual world. In our 

 Chapter V. we saw that space and time did not themselves 

 correspond to actual perceptions, but were modes under 

 which we perceived, and by which we discriminated, 

 groups of sense-impressions. So motion as the combina- 



