128 MYSTICISM AND LOGIC 



regarding what we see as physical and (in one oi 

 several possible senses) outside the mind, but is 

 probably wrong in supposing that it continues to exist 

 when we are no longer looking at it. It seems to 

 me that the whole discussion of matter has been obscured 

 by two errors which support each other. The first of these 

 is the error that what we see, or perceive through any of 

 our other senses, is subjective : the second is the belief 

 that what is physical must be persistent. Whatever 

 physics may regard as the ultimate constituents of matter, 

 it always supposes these constituents to be indestructible. 

 Since the immediate data of sense are not indestructible 

 but in a state of perpetual flux, it is argued that these 

 data themselves cannot be among the ultimate con- 

 stituents of matter. I believe this to be a sheer mistake. 

 The persistent particles of mathematical physics I regard 

 as logical constructions, symbolic fictions enabling us to 

 express compendiously very complicated assemblages of 

 facts ; and, on the other hand, I believe that the actual 

 data in sensation, the immediate objects of sight or touch 

 or hearing, are extra-mental, purely physical, and among 

 the ultimate constituents of matter. 



My meaning in regard to the impermanence of physical 

 entities may perhaps be made clearer by the use of Berg- 

 son's favourite illustration of the cinematograph. When 

 I first read Bergson's statement that the mathematician 

 conceives the world after the analogy of a cinematograph, 

 I had never seen a cinematograph, and my first visit to 

 one was determined by the desire to verify Bergson's 

 statement, which I found to be completely true, at least 

 so far as I am concerned. When, in a picture palace, we 

 see a man rolling down hill, or running away from the 

 police, or falling into a river, or doing any of those other 

 things to which men in such places are addicted, we know 



