[89] It would be instructive to draw up a list of the celebrated historical works, such as Augustin Thierry's _Histoire de la Conquête de l'Angleterre par les Normands_, whose authority has been completely destroyed after the authorship of their sources has been studied. Nothing amuses the gallery more than to see an historian convicted of having built a theory on falsified documents. Nothing is more calculated to cover an historian with confusion than to find that he has fallen into the error of treating seriously documents which are no documents at all. [90] One of the crudest (and commonest) forms of "uncritical method" is that which consists in employing as if they were documents, and placing on the same footing as documents, the utterances of modern authors on the subject of documents. Novices do not make a sufficient distinction, in the works of modern authors, between what is added to the original source and what is taken from it. [91] See a list of examples in Bernheim's _Handbuch_, pp. 283, 289. [92] It is because it is necessary to subject documents of mediæval and ancient history to the most searching criticism in respect of authorship that the study of antiquity and the middle ages passes for more "scientific" than that of modern times. The truth is, that it is merely hampered by more preliminary difficulties. [93] _Revue philosophique_, 1887, ii. p. 170. [94] The theory of the critical investigation of authorship is now settled, _ne varietur_; it is given in detail in Bernheim's _Lehrbuch_, pp. 242-340. For this reason we have had no scruple in dismissing it with a short sketch. In French, the introduction of M. G. Monod to his _Études critiques sur les sources de l'histoire mérovingienne_ (Paris, 1872, 8vo) contains elementary considerations on the subject. Cf. _Revue Critique_, 1873, i. p. 308. [95] Renan, _Feuilles détachées_, p. 103. [96] It would be very interesting to have information on the methods of work of the great scholars, particularly those who undertook long tasks of collection and classification. Some information of this kind is to be found in their papers, and occasionally in their correspondence. On the methods of Du Cange, see L. Feugère, _Étude sur la vie et les ouvrages de Du Cange_ (Paris, 1858, 8vo), pp. 62 _sqq._ [97] See J. G. Droysen, _Grundriss der Historik_, p. 19: "Critical classification does not exclusively adopt the chronological point of view.... The more varied the points of view which criticism uses to group materials, the more solid are the results yielded by converging lines of inquiry."