V. The problem of historical method may be finally stated as follows. Out of the different elements we find in documents we form mental images. Some of these, relating entirely to physical objects, are furnished to us by illustrative monuments, and they directly represent some of the physical aspects of the things of the past. Most of them, however, including all the images we form of psychic facts, are constructed on the model either of ancient representations, or, more frequently, of the facts we have observed in our own experience. Now, the things of the past were only partially similar to the things of the present, and it is precisely the points of difference which make history interesting. How are we to represent to ourselves these elements of difference for which we have no model? We have never seen a company of men resembling the Frankish warriors, and we have never personally experienced the feelings which Clovis had when setting out to fight against the Visigoths. How are we to make our imagination of facts of this kind harmonise with the reality? Practically, what happens is as follows. Immediately on the reading of a sentence in a document an image is formed in our minds by a spontaneous operation beyond our control. This image is based on a superficial analogy, and is, as a rule, grossly inaccurate. Any one who searches his memory may recall the absurd manner in which he first represented to himself the persons and scenes of the past. It is the task of history to rectify these images gradually, by eliminating the false elements one by one, and replacing them by true ones. We have seen red-haired people, bucklers, and Frankish battle-axes (or at least drawings of these objects); we bring these elements together, in order to correct our first mental image of the Frankish warriors. The historical image thus ends by becoming a combination of features borrowed from different experiences. It is not enough to represent to oneself isolated persons, objects, and actions. Men and their actions form part of a whole, of a society and of a process of evolution. It is, therefore, further necessary to represent to oneself the relations between different men and different actions (nations, governments, laws, wars). But in order to imagine relations it is necessary to have a conception of collectivities or wholes, and the documents only give isolated elements. Here again the historian is obliged to use a subjective method. He imagines a society or a process of evolution, and in this imaginary framework he disposes the elements furnished by the documents. Thus, whereas biological classification is guided by the objective observation of physical units, historical classification can only be effected upon subjective units existing in the imagination.