CAUSATION AND TIME'S ARROW 4&) 



be recognised if the closed system of the world were 

 broken into by standards foreign to it. 



For convenience I shall call the relation of effect to 

 cause causation, and the symmetrical relation which does 

 not distinguish between cause and effect causality. In 

 primary physics causality has completely replaced 

 causation. Ideally the whole world past and future is 

 connected into a deterministic scheme by relations of 

 causality. Up till very recently it was universally held 

 that such a determinate scheme must exist (possibly 

 subject to suspension by supernatural agencies outside 

 the scope of physics) ; we may therefore call this the 

 "orthodox" view. It was, of course, recognised that we 

 were only acquainted with part of the structure of this 

 causal scheme, but it was the settled aim of theoretical 

 physics to discover the whole. 



This replacement in orthodox science of causation by 

 causality is important in one respect. We must not let 

 causality borrow an intuitive sanction which really 

 belongs only to causation. We may think we have an 

 intuition that the same cause cannot have two alternative 

 effects; but we do not claim any intuition that the same 

 effect may not spring from two alternative causes. For 

 this reason the assumption of a rigid determinateness 

 enforced by relations of causality cannot be said to be 

 insisted on by intuition. 



What is the ground for so much ardent faith in the 

 orthodox hypothesis that physical phenomena rest ulti- 

 mately on a scheme of completely deterministic laws? 

 I think there are two reasons — 



(i) The principal laws of Nature which have been 

 discovered are apparently of this deterministic type, 

 and these have furnished the great triumphs of physical 

 prediction. It is natural to trust to a line of progress 



