SECT. 10.] Probability before and after the event. 287 



This puts a broad distinction, in popular estimation, between 

 what may be called the objective certainty of the past and of 

 the future, a distinction, however, which from the standing- 

 point of a science of inference ought to have no existence. 



In consequence of this, when we apply to the past and 

 the future respectively the somewhat ambiguous expression 

 the chance of the event, it commonly comes to bear very 

 different significations. Applied to the future it bears its 

 proper meaning, namely, the value to be assigned to a con 

 jecture upon statistical grounds. It does so, because in this 

 case hardly any one has more to judge by than such con 

 jectures. But applied to the past it shifts its meaning, 

 owing to the fact that whereas some men have conjectures 

 only, others have positive knowledge. By the chance of the 

 event is now often meant, not the value to be assigned to a 

 conjecture founded on statistics, but to such a conjecture 

 derived from and enforced by any body else s conjecture, that 

 is by his knowledge and his testimony. 



10. There is a class of cases in apparent opposition to 

 some of the statements in this chapter, but which will be 

 found, when examined closely, decidedly to confirm them. 

 I am walking, say, in a remote part of the country, and sud 

 denly meet with a friend. At this I am naturally surprised. 

 Yet if the view be correct that we cannot properly speak 

 about events in themselves being probable or improbable, 

 but only say this of our conjectures about them, how do we 

 explain this ? We had formed no conjecture beforehand, 

 for we were not thinking about anything of the kind, but 

 yet few would fail to feel surprise at such an incident. 



The reply might fairly be made that we had formed 

 such anticipations tacitly. On any such occasion every 

 one unconsciously divides things into those which are known 

 to him and those which are not. During a considerable 



