ON THE NOTION OF CAUSE 223 



and therefore could not be expected to realise that 

 induction itself, their own darling, required a logical 

 principle which obviously could not be proved induc- 

 tively, and must therefore be a priori if it could be 

 known at all. 



The view that the law of causality itself is a priori 

 cannot, I think, be maintained by anyone who realises 

 what a complicated principle it is. In the form which 

 states that " every event has a cause ' it looks simple ; 

 but on examination, " cause ' is merged in " causal law," 

 and the definition of a " causal law ' is found to be far 

 from simple. There must necessarily be some a priori 

 principle involved in inference from the existence of one 

 thing to that of another, if such inference is ever valid ; 

 but it would appear from the above analysis that the 

 principle in question is induction, not causality. Whether 

 inferences from past to future are valid depends wholly, 

 if our discussion has been sound, upon the inductive 

 principle : if it is true, such inferences are valid, and if 

 it is false, they are invalid. 



IV. I come now to the question how the conception of 

 causal laws which we have arrived at is related to the 

 traditional conception of cause as it occurs in philosophy 

 and common sense. 



Historically, the notion of cause has been bound up 

 with that of human volition. The typical cause would 

 be the fiat of a king. The cause is supposed to be 

 " active," the effect " passive." From this it is easy to 

 pass on to the suggestion that a " true ' cause must 

 contain some prevision of the effect ; hence the effect 

 becomes the " end ' at which the cause aims, and tele- 

 ology replaces causation in the explanation of nature. 

 But all such ideas, as applied to physics, are mere 

 anthropomorphic superstitions. It is as a reaction against 



