of all their evolutions would not be enough to exhaust the subject-matter of history. There remains a number of unique facts which we cannot pass over, because they explain the origin of certain states of society, and form the starting-points of evolutions. How could we study the institutions or the evolution of France if we ignored the conquest of Gaul by Cæsar and the invasion of the Barbarians?
This necessity of studying unique facts has caused it to be said that history cannot be a science, for every science has for its object that which is general. History is here in the same situation as cosmography, geology, the science of animal species: it is not the abstract knowledge of the general relations between facts, it is a study which aims at explaining reality. Now, reality exists but once. There has been but a single evolution of the world, of animal life, of humanity. In each of these evolutions the successive facts have not been the product of abstract laws, but of the concurrence, at each moment, of several circumstances of different nature. This concurrence, sometimes called chance, has produced a series of accidents which have determined the particular course taken by evolution. Evolution can only be understood by the study of these accidents; history is here on the same footing as geology or palæontology.
Thus scientific history may go back to the accidents, or events, which traditional history collected for literary reasons, because they struck the imagination, and employ them for the study of evolution. We may thus look for the facts which have influenced the evolution of each one of the habits of humanity. Each event will be arranged under its date in the evolution which