The set of general questions will only apply to phenomena of constant occurrence: it cannot anticipate the thousands of local or accidental events which enter into the life of an individual or a nation; it will, therefore, not contain all the questions which the historian must answer before he can give a complete picture of the past. The detailed study of the facts will require the use of lists of questions entering more into detail, and differing according to the nature of the events, the men, or the societies studied. In order to frame these lists, we begin by setting down those questions or matters of detail which are suggested by the mere reading of the documents; but for the purpose of arranging these questions, often indeed for the purpose of making the list complete, recourse must be had to the systematic _a priori_ method. Among the classes of facts, the persons, and the societies with which we are well acquainted (either from direct observation or from history), we look for those which resemble the facts, the persons, or the societies which we wish to study. By analysing the scheme of arrangement used in the scientific treatment of these familiar cases we shall learn what questions ought to be asked in reference to the analogous cases which we propose to investigate. Of course the model must be chosen intelligently; we must not apply to a barbarous society a list of questions framed on the study of a civilised nation, and ask with regard to a feudal domain what agents corresponded to each of our ministers of state--as Boutaric did in his study of the administration of Alphonse of Poitiers. This method of drawing up lists of questions which bases all historical construction on an _a priori_ procedure, would be objectionable if history really were a science of observation; and perhaps some will think it compares very unfavourably with the _a posteriori_ methods of the natural sciences. But its justification is simple: it is the only method which it is possible to employ, and the only method which, as a matter of fact, ever has been employed. The moment an historian attempts to put in order the facts contained in documents, he constructs out of the knowledge he has (or thinks he has) of human affairs a scheme of arrangement which is the equivalent of a list of questions--unless, perhaps, he adopts a scheme which one of his predecessors has constructed in a similar manner. But when this work has been performed unconsciously, the scheme of arrangement remains incomplete and confused. Thus it is not a case of deciding whether to work with or without an _a priori_ set of questions--we must work with such a set in any case--the choice merely lies between the unconscious use of an incomplete and confused set of questions and the conscious use of a precise and complete set. VI. We can now sketch the plan of historical construction in a way which will determine the series of synthetic operations necessary to raise the edifice.