The general history of individual facts was developed before the special histories. It contains the residue of facts which have not found a place in the special histories, and has been reduced in extent by the formation and detachment of special branches. As general facts are principally of a political nature, and as it is more difficult to organise these into a special branch, general history has in practice been confounded with political history (_Staatengeschichte_).[197] Thus political historians have been led to make themselves the champions of general history, and to retain in their constructions all the general facts (migrations of peoples, religious reforms, inventions, and discoveries) necessary for the understanding of political evolution. In order to construct general history it is necessary to look for all the facts which, because they have produced changes, can explain either the state of a society or one of its evolutions. We must search for them among all classes of facts, displacements of population, artistic, scientific, religious, technical innovations, changes in the _personnel_ of government, revolutions, wars, discoveries of countries. That which is important is that the fact should have had a decisive influence. We must therefore resist the natural temptation to divide facts into great and small. It goes against the grain to admit that great effects may have had small causes, that Cleopatra's nose may have made a difference to the Roman Empire. This repugnance is of a metaphysical order; it springs from a preconceived opinion on the government of the world. In all the sciences which deal with an evolution we find individual facts which serve as starting-points for series of vast transformations. A drove of horses brought by the Spanish has stocked the whole of South America. In a flood a branch of a tree may dam a current and transform the aspect of a valley. In human evolution we meet with great transformations which have no intelligible cause beyond an individual accident.[198] In the sixteenth century England changed its religion three times on the death of a sovereign (Henry VIII., Edward VI., Mary). Importance not to be measured by the initial fact, but by the facts which resulted from it. We must not, therefore, deny _a priori_ the action of individuals and discard individual facts. We must examine whether a given individual was in a position to make his influence strongly felt. There are two cases in which we may assume that he was: (1) when his action served as an example to a mass of men and created a tradition, a case frequent in art, science, religion, and technical matters; (2) when he had power to issue commands and direct the actions of a mass of men, as is the case with the heads of a state, an army, or a church. The episodes in a man's life may thus become important facts. Accordingly, in the scheme of historical classification a place should be assigned for persons and events.