THE NEW EPISTEMOLOGICAL OUTLOOK 305 



though the practical change is unimportant there are 

 fundamental theoretical consequences. All probabilities 

 rest on a basis of a priori probability, and we cannot say 

 whether probabilities are large or small without having 

 assumed such a basis. In agreeing to accept those of our 

 calculated probabilities which are very high as virtually 

 equivalent to certainties on the old scheme, we are as it 

 were making our adopted basis of a priori probability 

 a constituent of the world-structure — adding to the 

 world a kind of symbolic texture that cannot be ex- 

 pressed on the old scheme. 



On the atomic scale of phenomena the probabilities 

 are in general well-balanced, and there are no "naps" 

 for the scientific punter to put his shirt on. If a body is 

 still defined as a bundle of pointer readings (or highly 

 probable pointer readings) there are no "bodies" on 

 the atomic scale. All that we can extract is a bundle of 

 probabilities. That is in fact just how Schrodinger tries 

 to picture the atom — as a wave centre of his probability 

 entity i|>. 



We commonly have had to deal with probabilities 

 which arise through ignorance. With fuller knowledge 

 we should sweep away the references to probability and 

 substitute the exact facts. But it appears to be a funda- 

 mental point in Schrodinger's theory that his probabili- 

 ties are not to be replaced in that way. When his ip is 

 sufficiently concentrated it indicates the point where the 

 electron is; when it is diffused it gives only a vague 

 indication of the position. But this vague indication is 

 not something which ideally ought to be replaced by 

 exact knowledge; it is ip itself which acts as the source 

 of the light emitted from the atom, the period of the 

 light being that of the beats of i|>. I think this means 

 that the spread of ty is not a symbol for uncertainty aris- 



