tentional or unconscious, which writers are apt to make in passages which they rapidly quote, and again of the individual habits of quotation found in this or that particular writer. In all these cases on the one hand comparative excellence is various and divided; and on the other an exact study of documents will go a great way towards changing vague guesses about possible errors into positive knowledge of the limits within which undoubted errors have been actually found to exist. The corrective process is strictly analogous to that by which evidence from Transcriptional Probability is acquired and reduced to order: but in the present case there is less liability to error in application, because we are drawing inferences not so much from the average ways of scribes as a class as from the definite characteristics of this or that documentary witness.
46. The true range of individuality of text cannot moreover be exactly measured by the range of contents of an existing document. We have no right to assume without verification the use of the same exemplar or exemplars from the first page to the last. A document containing more books than one may have been transcribed either from an exemplar having identical contents, or from two or more exemplars each of which contained a smaller number of books; and these successive exemplars may have been of very various or unequal excellence. As regards alterations made by the transcriber himself, a generalisation obtained from one book would be fairly valid for all the rest. But as regards what is usually much more important, the antecedent text or texts received by him, the prima facie presumption that a generalisation obtained in one book will be applicable in another cannot safely be trusted until the recurrence of
