SIR JAMES JEANS 247 



solve; it merely verified the substantiality of matter. 

 And however science may progress, stones must always 

 remain substantial bodies, just because they and their 

 class form the standard by which we define the quality 

 of substantiality. 



It has been suggested that the lexicographer might 

 really have disproved the Berkeleian philosophy if he 

 had chanced to kick, not a stone but a hat in which 

 some small boy had surreptitiously concealed a brick. 

 As Sir Peter Chalmers Michell puts it, "the element 

 of surprise is sufficient warrant for external reality," 

 and "a second warrant is permanence with change — 

 permanence In your own memory, change in exter- 

 nality." This, of course, merely disproves the sophist 

 error of "all this is a creation of my own mind, and 

 exists in no other mind." But it is hard to do any- 

 thing in life which does not disprove this. The argu- 

 ment from surprise, and from new knowledge in gen- 

 eral, is powerless against the concept of a universal 

 mind of which your mind and mine, the mind which 

 surprises and that which is surprised, are units or even 

 excrescences. Each individual brain cell cannot be 

 acquainted with all the thoughts which are passing 

 through the brain as a whole. 



Yet the fact that we possess no absolute extraneous 

 standard against which to measure substantiality, does 

 not preclude our saying that two things have the same 

 degree, or different degrees of substantiality. If I 

 dash my foot against a stone in my dreams, I shall 

 probably wake up with a pain in my foot, to discover 

 that the stone of my dreams was literally a creation 

 of my mind and of mine alone, prompted by a nerve- 

 impulse originating in my foot. This stone may t)^ify 



