The problem consists in this: that our doctrine necessitates a new criticism of the sources of history. And I do not wish to be understood as speaking exclusively of the criticism of documents in the proper and ordinary sense of the word, because as for this we may content ourselves with what is delivered to us ready made by the critics, the scholars, and the professional philologists. But I would speak of that immediate source which is behind the so called documents properly and which, before expressing itself and fixing itself in these, resides in the spirit and in the form of the consciousness in which the actors accounted to themselves for the motives of their own work. This spirit, that is to say, this consciousness, is often inadequate to the causes which we are now in a position to discover, from which it follows that the actors seem to us enveloped, as it were, in a circle of illusions. To strip the historic facts from these envelopes which clothe the very facts while they are developing--this is to make a new criticism of the sources in the realistic sense of the word and not in the formal documentary sense. It is, in short, to make react upon the knowledge of past conditions the consciousness of which we are now capable, and thereby to reconstruct them anew. But this revision of the most direct sources, if it marks the extreme limit of the historic self-consciousness which may be reached, may be an occasion for falling into a serious error. As we place ourselves at a point of view which is beyond the ideological views to which the actors in history were indebted for a consciousness of their work and in which they often found both the motives and the justification of their action, we may falsely believe that these ideological views were a pure appearance, a simple artifice, a pure illusion in the vulgar sense of the word. Martin Luther, like the other great reformers, his contemporaries, never knew, as we know to-day, that the Reformation was but an episode in the development of the Third Estate, and an economic revolt of the German nation against the exploitation of the Papal court. He was what he was, as an agitator and a politician, because he was wholly taken up with the belief which made him see in the class movement which gave an impulse to the agitation a return to true Christianity and a divine necessity in the vulgar course of events. The study of remote effects, that is to say, the increasing strength of the bourgeoisie of the cities against the feudal lords, the increase of the territorial dominion of the princes at the expense of the inter-territorial and super-territorial power of the emperor and the pope, the violent repression of the movement of the peasants and the more properly proletarian movement of the Anabaptists permit us now to reconstruct the authentic history of the economic causes of the Reformation, particularly in the final proportions which it took, which is the best of proofs.