So the application of our doctrine must be kept for a moment to the exposition and the study of definite parts of history. The modern forms are clear to all. The economic developments of the bourgeoisie, the manifest knowledge of the different obstacles which it has had to overcome in the different countries, and, consequently, the development of the different revolutions, taking this word in its broadest sense, contribute to make our understanding of it easy. To our eyes the pre-history of the bourgeoisie, at the moment of the decline of the Middle Ages, is equally clear, and it would not be difficult to find, for example, in the development of the city of Florence, an attested series of developments, in which the economic and statistical movement finds a perfect correspondence in the political relations and a sufficient illustration in the contemporary development of intelligence already reduced into prose and stripped, in great part, of ideological illusions. Nor would it be impossible to reduce, now, under the definite visual angle of materialism, the whole of ancient Roman history. But for that, and particularly, for the primitive period, there are no direct sources; they are, on the contrary, abundant in Greece, from popular tradition, the epic, and the authentic juridical inscriptions, down to the pragmatic studies of the historical social relations. At Rome, on the other hand, the struggles for political rights carry with them almost always the economic reasons upon which they rest. Thus, the decline of definite classes, the formation of new classes, the movement of conquest, the change of the laws and of the forms of political array, appear to us with perfect clearness. This Roman history is hard and prosaic; it was never clad with these ideological complements which were suited to Greek life. The rigid prose of conquest, of planned colonization, of institutions and of the forms of law, conquered and devised for solving the problems arising from definite frictions and contrasts, makes all Roman history a chain of events which follow each other in a sequence which is grossly evident.