GROUNDS OF DISBELIEF. 171 



tion. In the cast of a perfectly fair die, the chances are five 

 to one against throwing ace, that is, ace will be thrown on an 

 average only once in six throws. But this is no reason against 

 believing that ace was thrown on a given occasion, if any 

 credible witness asserts it ; since though ace is only thrown 

 once in six times, some number which is only thrown once in 

 six times must have been thrown if the die was thrown at all. 

 The improbability, then, or in other words, the unusualness, 

 of any fact, is no reason for disbelieving it, if the nature of the 

 case renders it certain that either that or something equally 

 improbable, that is, equally unusual, did happen. Nor is this 

 all : for even if the other five sides of the die were all twos, or 

 all threes, yet as ace would still on the average come up once 

 in every six throws, its coming up in a given throw would be 

 not in any way contradictory to experience. If we disbelieved 

 all facts which had the chances against them beforehand, we 

 should believe hardly anything. We are told that A. B. died 

 yesterday : the moment before we were so told, the chances 

 against his having died on that day may have been ten 

 thousand to one ; but since he was certain to die at some time 

 or other, and when he died must necessarily die on some par- 

 ticular day, while the preponderance of chances is very great 

 against every day in particular, experience affords no ground 

 for discrediting any testimony which may be produced to the 

 event's having taken place on a given day. 



Yet it has been considered, by Dr. Campbell and others, as 

 a complete answer to Hume's doctrine (that things are incre- 

 dible which are contrary to the uniform course of experience) , 

 that we do not disbelieve, merely because the chances were 

 against them, things in strict conformity to the uniform course 

 of experience ; that we do not disbelieve an alleged fact merely 

 because the combination of causes on which it depends occurs 

 only once in a certain number of times. It is evident that 

 whatever is shown by observation, or can be proved from laws 

 of nature, to occur in a certain proportion (however small) of 

 the whole number of possible cases, is not contrary to expe- 

 rience ; though we are right in disbelieving it, if some other 

 supposition respecting the matter in question involves on the 



