CONSTITUENTS OF MATTER 127 



or unconscious inference, how much is mental inter- 

 pretation, and how doubtful is the residuum which can 

 be regarded as crude datum. From these facts it is 

 argued by the psychologists that the notion of a datum 

 passively received by the mind is a delusion, and it is 

 argued by the physiologists that even if a pure datum of 

 sense could be obtained by the analysis of experience, 

 still this datum could not belong, as common sense sup- 

 poses, to the outer world, since its whole nature is con- 

 ditioned by our nerves and sense organs, changing as 

 they change in ways which it is thought impossible to 

 connect with any change in the matter supposed to be 

 perceived. This physiologist's argument is exposed to 

 the rejoinder, more specious than solid, that our know- 

 ledge of the existence of the sense organs and nerves is 

 obtained by that very process which the physiologist has 

 been engaged in discrediting, since the existence of the 

 nerves and sense organs is only known through the 

 evidence of the senses themselves. This argument may 

 prove that some reinterpretation of the results of phy- 

 siology is necessary before they can acquire metaphysical 

 validity. But it does not upset the physiological argu- 

 ment in so far as this constitutes merely a reductio ad 

 absurdum of naive realism. 



These various lines of argument prove, I think, that 

 some part of the beliefs of common sense must be aban- 

 doned. They prove that, if we take these beliefs as a 

 whole, we are forced into conclusions which are in part 

 self-contradictory ; but such arguments cannot of them- 

 selves decide what portion of our common-sense beliefs 

 is in need of correction. Common sense believes that 

 what we see is physical, outside the mind, and continuing 

 to exist if we shut our eyes or turn them in another 

 direction. I believe that common sense is right in 



