t mention but would have done if he had
known of it. Arguments may also be founded on the circumstance that
particular facts are mentioned with approval, or particular opinions
expressed, and help us to make a conjectural estimate of the status, the
environment, and the character of the author.

When the internal analysis of a document is carefully performed, it
generally gives us a tolerably accurate notion of its authorship. By
means of a methodical comparison, instituted between the various
elements of the documents analysed and the corresponding elements of
similar documents whose authorship was known with certainty, the
detection of many a forgery[82] has been rendered possible, and
additional information acquired about the circumstances under which most
genuine documents have been produced.

The results obtained by internal analysis are supplemented and verified
by collecting all the external evidence relative to the document under
criticism which can be found scattered over the documents of the same or
later epochs--quotations, biographical details about the author, and so
on. Sometimes there is a significant absence of any such information:
the fact that an alleged Merovingian charter has not been quoted by
anybody before the seventeenth century, and has only been seen by a
seventeenth-century scholar who has been convicted of fraud, suggests
the thought that it is modern.

II. Hitherto we have considered only the simplest case, in which the
document under examination is the work of a single author. But many
documents have, at different times, received additions which it is
important to distinguish from the original text, in order that we may
not attribute to X, the author of the text, what really belongs to Y or
Z, his unforeseen collaborators.[83] There are two kinds of
additions--interpolations and continuations. To interpolate is to insert
into the text words or sentences which were not in the author's
manuscript.[84] Usually interpolations are accidental, due to the
negligence of the copyist, and explicable as the introduction into the
text of interlinear glosses or marginal notes; but there are cases where
some one has deliberately added to (or substituted for) the author's
text words or sentences out of his own head, for the sake of
completeness, ornament, or emphasis. If we had before us the manuscript
in which the deliberate interpolation was made, the appearance of the
added matter and the traces