SECT. 4] Testimony. 397 



question, but these would not differ sufficiently in their 

 results to make it worth our while to do so. In other words, 

 the different propositions which are applicable to the case in 

 point arrange themselves into a limited number of groups, 

 which, and which only, need be taken into account ; whence 

 the range of choice amongst them is very much diminished 

 in practice. 



4. The reasons for the conditions above described are 

 not difficult to detect. Where these conditions exist the 

 process of selecting a series or class to which to refer any 

 individual is very simple, and the selection is, for the par 

 ticular purposes of inference, final. In any case of insurance, 

 for example, the question we have to decide is of the very 

 simple kind ; Is A.B. a man of a certain age ? If so one in 

 fifty in his circumstances will die in the course of the year. 

 If any further questions have to be decided they would be of 

 the following description. Is A.B. a healthy man ? Does he 

 follow a dangerous trade ? But here too the classes in 

 question are but few, and the limits by which they are 

 bounded are tolerably precise ; so that the reference of an 

 individual to one or other of them is easy. And when we 

 have once chosen our class we remain untroubled by any 

 further considerations ; for since no other statistics are sup 

 posed to offer a materially different average, we have no 

 occasion to take account of any other properties than those 

 already noticed. 



The case of games of chance, already referred to, offers 

 of course an instance of these conditions in an almost ideal 

 state of perfection ; the same circumstances which fit them 

 so eminently for the purposes of fair gambling, fitting them 

 equally to become examples in Probability. When a die is 

 to be thrown, all persons alike stand on precisely the same 

 footing of knowledge and of ignorance about the result ; the 



