PREDICTABILITY OF EVENTS 299 



(2) Whether or not there is a causal scheme at the 

 base of atomic phenomena, modern atomic theory is not 

 now attempting to find it; and it is making rapid prog- 

 ress because it no longer sets this up as a practical aim. 

 We are in the position of holding an epistemological 

 theory of natural knowledge which does not correspond 

 to actual aim of current scientific investigation. 



Predictability of Events. Let us examine a typical case 

 of successful scientific prediction. A total eclipse of the 

 sun visible in Cornwall is prophesied for 1 1 August 

 1999. It is generally supposed that this eclipse is 

 already predetermined by the present configuration of 

 the sun, earth and moon. I do not wish to arouse 

 unnecessary misgiving as to whether the eclipse will 

 come off. I expect it will; but let us examine the grounds 

 of expectation. It is predicted as a consequence of the 

 law of gravitation — a law which we found in chapter vil 

 to be a mere truism. That does not diminish the value 

 of the prediction; but it does suggest that we may not be 

 able to pose as such marvellous prophets when we come 

 up against laws which are not mere truisms. I might 

 venture to predict that 2 + 2 will be equal to 4 even in 

 1999; but if this should prove correct it will not help 

 to convince anyone that the universe (or, if you like, the 

 human mind) is governed by laws of deterministic type. 

 I suppose that in the most erratically governed world 

 something can be predicted if truisms are not ex- 

 cluded. 



But we have to look deeper than this. The law of 

 gravitation is only a truism when regarded from a 

 macroscopic point of view. It presupposes space, and 

 measurement with gross material or optical arrange- 

 ments. It cannot be refined to an accuracy beyond the 



