SECT. 32.] Modality. 329 



large number of ordinary representative cases are submitted 

 to a court consisting even of exactly similar materials to the 

 one whose decisions we wish to test. Provided always that we 

 make the monstrous assumption that the judgments of men 

 about matters which deeply affect them are independent 

 in the sense in which the tosses of pence are independent, 

 then the statistics of mere agreement and disagreement will 

 serve our purpose. We might be able to say, for instance, 

 that a jury of a given number, deciding by a given majority, 

 were right nine times out of ten in their verdict. Conclu 

 sions of this kind, in reference to the French courts, are 

 what Poisson has attempted at the end of his great work on 

 the Probability of Judgments ; though I do not suppose that 

 he attached much numerical accuracy to his results. 



A scarcely more hopeful means would be found by a 

 reference to certain cases of legal presumptions. A con 

 clusive presumption is denned as follows : &quot; Conclusive, or 

 as they are elsewhere termed imperative or absolute pre 

 sumptions of law, are rules determining the quantity of evi 

 dence requisite for the support of any particular averment 

 which is not permitted to be overcome by any proof that the 

 fact is otherwise 1 .&quot; A large number of such presumptions 

 will be found described in the text-books, but they seem to 

 refer to matters far too vague, for the most part, to admit of 

 any reduction to statistical frequency of occurrence. It is 

 indeed maintained by some authorities that any assignment 

 of degree of Probability is not their present object, but that 

 they are simply meant to exclude the troublesome delays 



x. Then the chance of their agree- ment is confirmed by the second, we 



ing is x 2 + (l x) 2 , for they agree if have the means of determining or. 



both are right or both wrong. If 1 Taylor on Evidence : the latter 



the statistical frequency of this agree- part of the extract does not seem 



ment is known, that is, the fre- very clear, 

 quency with which the first judg- 



