SECT. 6.] Credibility of Extraordinary Stories. 411 



can do is to endeavour, as best we may, to ascertain, from 

 the circumstances of the case, what number of alternatives* 

 the witness may be supposed to have had before him. When 

 he simply testifies to some matter well known to be in dis 

 pute, and does not go much into detail, we may fairly con 

 sider that there were practically only the two alternatives- 

 before him of saying yes or no. When, on the other hand, 

 he tells a story of a more original kind, or (what comes to 

 much the same thing) goes into details, we must regard him 

 as having a wide comparative range of alternatives before 

 him. 



These two classes of examples, viz. that of the black and 

 white balls, in which only one form of error is possible, and 

 the numbered balls, in which there may be many forms of 

 error, are the only two which we need notice. In practice it 

 would seem that they may gradually merge into each other, 

 according to the varying ways in which we choose to frame 

 our question. Besides asking, Did you see A strike B ? and, 

 What did you see ? we may introduce any number of inter 

 mediate leading questions, as, What did A do ? What did 

 he do to 5? and so on. In this way we may gradually narrow 

 the possible openings to wrong statement, and so approach 

 to the direct alternative question. But it is clear that all 

 these cases may be represented numerically by a supposed 

 diminution in the number of the balls which are thus distin 

 guished from each other. 



6. Of the two plans mentioned in 4 we will begin 

 with the latter, as it is the only methodical and scientific one 

 which has been proposed. Suppose that there is a bag with 

 1000 balls, only one of which is white, the rest being all 

 black. A ball is drawn at random, and our witness whose 

 veracity is T % reports that the white ball was drawn. Take 

 a great many of his statements upon this particular subject, 



