ON THE NOTION OF CAUSE 187 



most once, and the law would cease to give information. 

 An " event," then, is a universal denned sufficiently 

 widely to admit of many particular occurrences in time 

 being instances of it. 



(2) The next question concerns the time-interval. 

 Philosophers, no doubt, think of cause and effect as 

 contiguous in time, but this, for reasons already given, is 

 impossible. Hence, since there are no infinitesimal time- 

 intervals, there must be some finite lapse of time T 

 between cause and effect. This, however, at once raises 

 insuperable difficulties. However short we make the 

 interval r, something may happen during this interval 

 which prevents the expected result. I put my penny in 

 the slot, but before I can draw out my ticket there is an 

 earthquake which upsets the machine and my calcula- 

 tions. In order to be sure of the expected effect, we 

 must know that there is nothing in the environment to 

 interfere with it. But this means that the supposed 

 cause is not, by itself, adequate to insure the effect. 

 And as soon as we include the environment, the prob- 

 ability of repetition is diminished, until at last, when the 

 whole environment is included, the probability of repeti- 

 tion becomes almost nil. 



In spite of these difficulties, it must, of course, be 

 admitted that many fairly dependable regularities of 

 sequence occur in daily life. It is these regularities that 

 have suggested the supposed law of causality ; where they 

 arc found to fail, it is thought that a better formulation 

 could have been found which would have never failed. 

 I am far from denying that there may be such sequences 

 which in fact never do fail. It may be that there will 

 never be an exception to the rule that when a stone of 

 more than a certain mass, moving with more than a 

 certain velocity, comes in contact with a pane of glass of 



