1. On the presumption that the general method of this treatise for the solution of questions in the theory of probabilities, has been sufficiently elucidated in the previous chapters, it is proposed here to enter upon one of its practical applications selected out of the wide field of social statistics, viz., the estimation of the probability of judgments. Perhaps this application, if weighed by its immediate results, is not the best that could have been chosen. One of the first conclusions to which it leads is that of the necessary insufficiency of any data that experience alone can furnish, for the accomplishment of the most important object of the inquiry. But in setting clearly before us the necessity of hypotheses as supplementary to the data of experience, and in enabling us to deduce with rigour the consequences of any hypothesis which may be assumed, the method accomplishes all that properly lies within its scope. And it may be remarked, that in questions which relate to the conduct of our own species, hypotheses are more justifiable than in questions such as those referred to in the concluding sections of the previous chapter. Our general experience of human nature comes in aid of the scantiness and imperfection of statistical records.