INTRODUCTORY EXPLANATION. 29 



Supreme Being, this theory leaves the question exactly 

 where it found it ; and the same of all questions of his- 

 torical evidence. If we were to assume fictitious data, 

 we might, as in all other sciences of inference, produce a 

 consequence which should be as true as the premises, 

 standing or falling with them. The science itself is 

 the deduct'on of the probability in a complicated case 

 from the probability in a known and simple case. But 

 where is the known and simple case in the historical 

 question ? In valuing testimony, no theory of the 

 method in which conflicting evidence should be com- 

 bined will help us to the original value of the several 

 parts of it, any more than an investigation of the 

 method of solving an equation will help us to a know- 

 ledge of the particular equations which apply in any 

 given case. 



The two great theoretical questions before us are : 

 I. What is the measure of probability ? II. What is 

 the way of using it ? The necessary preliminary to 

 application is, the result of the measurement in a case 

 to which the method of measuring can be applied, and 

 has been applied. The mistakes which have arisen from 

 confounding these considerations are numerous. For in- 

 stance, tell me how many times per cent, a given man will 

 be wrong in his judgment, and I can tell you exactly, 

 positively, and mathematically, how much more likely a 

 unanimous jury (not starved) is to have arrived at a true 

 decision, than another in which the voices are 8 to 4. 

 But that does not put me one step nearer to ascertaining 

 what is the per centage of erroneous conclusions in 

 the judgments of a single individual. The miscon- 

 ceptions just alluded to are equally prevalent with regard 

 to all the sciences ; a person who studies astronomy is 

 frequently asked what the moon is made of. 



Much of the objection, religious or not, made against 

 probability in general, is connected with the notion 

 already mentioned, (page 7.) that it is a fundamental 

 quality of events, external to ourselves, which is under 

 consideration : on which the rational feeling must be, 



