of events, what episodes, what groups of actors are still unknown to us; what facts enter or disappear from the field of our knowledge without our being able to trace their beginning or end. We ought to construct, mentally at any rate, a tabulated scheme of the points on which we are ignorant, in order to keep before our minds the distance separating the knowledge we have from a perfect knowledge.
(2) The value of our knowledge depends on the value of our documents. Criticism has given us indications on this point in each separate case, these indications, so far as relating to a given body of facts, must be summarised under a few heads. Does our knowledge come originally from direct observation, from written tradition, or from oral tradition? Do we possess several traditions of different bias, or a single tradition? Do we possess documents of different classes or of one single class? Is our information vague or precise, detailed or summary, literary or positive, official or confidential?
The natural tendency is to forget, in construction, the results yielded by criticism, to forget the incompleteness of our knowledge and the elements of doubt in it. An eager desire to increase to the greatest possible extent the amount of our information and the number of our conclusions impels us to seek emancipation from all negative restrictions. We thus run a great risk of using fragmentary and suspicious sources of information for the purpose of forming general impressions, just as if we were in possession of a complete record. It is easy to forget the existence of those facts which the documents do not describe (economic facts, slaves in antiquity), it is easy to exaggerate the space