SECT. 8.] Fallacies. 337 



logical right (so long as we confine ourselves to this view) to 

 make his surprise a ground for disbelieving the event. To 

 do this is to fall into the fallacy described at the commence 

 ment of this chapter. The fact of my not having been likely 

 to have guessed a thing beforehand is no reason in itself for 

 doubting it when I am informed of it. (2) Or I may stop 

 short of the events reported, and apply the rules of Proba 

 bility to the report itself. If so, what I mean is that such a 

 story as this now before me is of a kind very generally false, 

 and that I cannot therefore attach much credit to it now. 

 (3) Or I may accept the truth of the report, but doubt the 

 fact of the stranger having taken the book at random. If 

 so, what I mean is, that of men who take books in the way 

 described, only a small proportion will be found to have 

 taken them really at random ; the majority will do so because 

 they had by some means ascertained, or come to suspect, 

 what there was inside the book. 



Each of the above three meanings is a possible and a 

 legitimate meaning. The only requisite is that we should be 

 careful to ascertain which of them is present to the mind, so 

 as to select the appropriate statistics. The first makes in 

 itself the most legitimate use of Probability ; the drawback 

 being that at the time in question the functions of Pro 

 bability are superseded by the event being otherwise known. 

 The second or third, therefore, is the more likely meaning to 

 be present to the mind, for in these cases Probability, if it 

 could be practically made use of, would, at the time in 

 question, be a means of drawing really important inferences. 

 The drawbacks are the difficulty of finding such statistics, 

 and the extreme disturbing influence upon these statistics of 

 the circumstances of the special case. 



8. (II.) Closely connected with the tendency just 

 mentioned is that which prompts us to confound a true 

 v. 22 



