to each other, either by imitation and convention (language, rites, ceremonies), or from the influence of custom and obligatory regulations (social institutions, political institutions in countries where the authorities are obeyed). A large number is requisite for facts where individual initiative plays a more important part (art, science, morality), and sometimes, as in respect of private conduct, all generalisation is as a rule impossible.
VI. Descriptive formulæ are in no science the final result of the work. It still remains to group the facts in such a way as to bring out their collective import, it still remains to search for their mutual relations; these are the general conclusions. History, by reason of the imperfection of its mode of acquiring knowledge, needs, in addition, a preliminary operation for determining the bearing of the knowledge acquired.
The work of criticism has supplied us with nothing but a number of isolated remarks on the value of the knowledge which the documents have permitted us to acquire. These must be combined. We shall therefore take a whole group of facts entered under a common heading—a particular class of facts, a country, a period, an event—and we shall summarise the results yielded by the criticism of particular facts so as to obtain a general formula. We shall have to take into consideration: (1) the extent, (2) the value of our knowledge.
(1) We shall ask ourselves what are the blanks left by the documents. By working through the scheme used for the grouping of facts it is easy to discover what are the classes of facts on which we lack information. In the case of evolution, we notice which links are missing in the chain of successive modifications; in the case