It is obvious that these assumptions are not only distinct, but that they are independent of each other:--for one of them may be conclusively established, while the other is either disproved, or may remain questionable. A book may contain a true narrative of events, though not written by the author, or in the age, that has commonly been supposed. Or, on the other hand, it may undoubtedly be the production of the alleged author, but may deserve little credit as a professed record of facts. Thus, for example, the Cyropædia is, on good evidence, attributed to Xenophon; but there is little reason to suppose that it deserves to be considered as better than an historical romance:--the _genuineness_ of the work is certain; but its authenticity as a history is, at the best, questionable. Yet the first of these propositions is more independent of the second, than the second can be of the first. For when the antiquity and genuineness of an historical work has been clearly demonstrated, it is seldom difficult to fix the degree of credit that is due to the author; or to discover those particular points on which there may be reason to suspect his veracity, or to question the soundness of his judgment, or to doubt the accuracy of his information. It is then for the purpose of rendering these arguments and inferences intelligible, and more satisfactory also, than otherwise they would be, that, after giving a brief statement of this argument, we shall proceed to bring forward what relates to the manipulative and mechanical methods of multiplying copies of books, and to the diffusion, and preservation of these copies, in ancient times;--that is to say, in all times anterior to the invention of Printing, in the fifteenth century. CHAPTER II. STATEMENT OF THE CASE, AS TO THE AUTHENTICITY OF ANCIENT BOOKS. The antiquity and genuineness of the extant remains of ancient literature may be established by three lines of proof that are altogether independent of each other; and though, in any particular instance, one, or even two out of the three should be wanting, the remaining one may alone be perfectly conclusive:--When the three concur, they present a redundant demonstration of the facts in question. The _first_ line of proof relates to the history of certain copies of a work, which are now in existence. The _second_--traces the history of a work as it may be collected from the series of references made to it by succeeding writers. The _third_--is drawn from the known history of the _language_ in which the work is extant. For understanding what belongs to the first of these three lines of evidence we ought to be acquainted with various particulars relating to the modes of writing practised among ancient nations, and to the materials employed, and to what may be called the business-system by means of which an ancient writer placed himself in communication with his readers.