A NEW EPISTEMOLOGY 225 



turn becomes too rough and knocks the electron out of 

 the atom. 



Other examples of the reciprocal uncertainty have 

 been given, and there seems to be no doubt that it is 

 entirely general. The suggestion is that an association 

 of exact position with exact momentum can never be 

 discovered by us because there is no such thing in Nature. 

 This is not inconceivable. Schrodinger's model of the 

 particle as a wave-group gives a good illustration of how 

 it can happen. We have seen (p. 217) that as the posi- 

 tion of a wave-group becomes more defined the energy 

 (frequency) becomes more indeterminate, and vice versa. 

 I think that that is the essential value of Schrodinger's 

 theory; it refrains from attributing to a particle a kind 

 of determinacy which does not correspond to anything 

 in Nature. But I would not regard the principle of 

 indeterminacy as a result to be deduced from Schro- 

 dinger's theory; it is the other way about. The principle 

 of indeterminacy, like the principle of relativity, repre- 

 sents the abandonment of a mistaken assumption which 

 we never had sufficient reason for making. Just as we 

 were misled into untenable ideas of the aether through 

 trusting to an analogy with the material ocean, so we 

 have been misled into untenable ideas of the attributes 

 of the microscopic elements of world-structure through 

 trusting to analogy with gross particles. 



A New Epistemology. The principle of indeterminacy 

 is epistemological. It reminds us once again that the 

 world of physics is a world contemplated from within 

 surveyed by appliances which are part of it and subject 

 to its laws. What the world might be deemed like if 

 probed in some supernatural manner by appliances not 

 furnished by itself we do not profess to know. 



