We have the example of Marx, and there is an argument from fact which admits of no reply. But he was the first and the principal author of the decisive concepts of this doctrine, reducing it at once into an instrument of political orientation, in his character of an incomparable publicist, during the revolutionary period of 1848 to 1850. And then he applied it with the greatest precision in that essay entitled Eighteenth Brumaire of Louis Bonaparte, of which it may be said today, at a great distance, and after so many publications, if we except certain infinitesimal details and certain false forecasts, that it would be possible to make neither corrections nor important complements. I will not repeat, since I am not writing a bibliography, the list of the different writings of Marx or Engels--of which we have so many attempts from the Peasants' War (1850) down to his posthumous writings on The Present Unity of Germany--which are an application of the doctrine, nor those of their successors and of the popularizers of scientific socialism. Even in the socialist press we may read, from time to time, valuable attempts at explanation of certain political events, in which is found, precisely by reason of historic materialism, a clearness of vision which would be sought in vain among the writers and the disputants who have not yet torn away the fantastic veils and ideological envelopes of history. Here is not the place to take up the defense of an abstract thesis, as an advocate would do. It is evident, nevertheless, in all the histories which have been written up to the present time, that there is always at bottom, if not in the explicit intentions of the writers, certainly in their spirit, a tendency, a principle, a general view of life; and so this doctrine, which has enabled us to study the social structure in an objective manner, must finally direct with precision the researches of history, and must end in a narrative complete, transparent and integral. Helps are not lacking.