402 Testimony. [CHAP. xvi. 



reasonably be referred by every one who has the facts before 

 him. 



9. A criticism somewhat resembling the above has 

 been given by Mill (Logic, Bk. in. Chap, xviii. 3) upon 

 the applicability of the theory of Probability to the credi 

 bility of witnesses. But he has added other reasons which 

 do not appear to me to be equally valid ; he says &quot; common 

 sense would dictate that it is impossible to strike a general 

 average of the veracity, and other qualifications for true 

 testimony, of mankind or any class of them ; and if it were 

 possible, such an average would be no guide, the credibility of 

 almost every witness being either below or above the average.&quot; 

 The latter objection would however apply with equal force 

 to estimating the length of a man s life from tables of mor 

 tality ; for the credibility of different witnesses can scarcely 

 have a wider range of variation than the length of different 

 lives. If statistics of credibility could be obtained, and 

 could be conveniently appealed to when they were obtained, 

 they might furnish us in the long run with as accurate 

 inferences as any other statistics of the same general de 

 scription. These statistics would however in practice natu 

 rally and rightly be neglected, because there can hardly fail 

 to be circumstances in each individual statement which would 

 more appropriately refer it to some new class depending on 

 different statistics, and affording a far better chance of our 

 being right in that particular case. In most instances of 

 the kind in question, indeed, such a change is thus produced 

 in the mode of formation of our opinion, that, as already 

 pointed out, the mental operation ceases to be in any proper 

 sense founded on appeal to statistics 1 . 



1 It may be remarked also that principles of Probability in the 

 there is another reason which tends majority of the cases where testi- 

 to dissuade us from appealing to mony has to be estimated. It often, 



