to the knowledge of facts is one of the chief parts of Historical Methodology. It is the domain of criticism. The seven following chapters will be devoted to it. We shall endeavour, first of all, to give a very summary sketch of the general lines and main divisions of the subject.
I. We may distinguish two species of documents. Sometimes the past event has left a material trace (a monument, a fabricated article). Sometimes, and more commonly, the trace is of the psychological order—a written description or narrative. The first case is much simpler than the second. For there is a fixed relation between certain physical appearances and the causes which produced them; and this relation, governed by physical laws, is known to us. But a psychological trace, on the other hand, is purely symbolic: it is not the fact itself; it is not even the immediate impression made by the fact upon the witness's mind, but only a conventional symbol of that impression. Written documents, then, are not, as material documents are, valuable by themselves; they are only valuable as signs of psychological operations, which are often complicated and hard to unravel. The immense majority of the documents which furnish the historian with starting-points for his reasonings are nothing else than traces of psychological operations.
This granted, in order to conclude from a written document to the fact which was its remote cause—that is, in order to ascertain the relation which connects the document with the fact—it is necessary to reproduce the whole series of intermediate causes which have given rise to the document. It is necessary to revive in imagination the whole of that series of acts performed by the author of the document