sy to establish; the plagiarist, whether he
abridges or expands, nearly always betrays himself sooner or later.[86]

When there are three documents in a family their mutual relationships
are sometimes harder to specify. Let A, B, and C be the documents.
Suppose A is the common source: perhaps B and C copied it independently;
perhaps C only knew A through the medium of B, or B knew it only through
C. If B and C have abridged the common source in different ways, they
are evidently independent. When B depends on C, or _vice versa_, we have
the simplest case, treated in the preceding paragraph. But suppose the
author of C combined A and B, while B had already used A: the genealogy
begins to get complicated. It is more complicated still when there are
four, five, or more documents in a family, for the number of possible
combinations increases with great rapidity. However, if too many
intermediate links have not been lost, criticism succeeds in
disentangling the relationships by persistent and ingenious applications
of the method of repeated comparisons. Modern scholars (Krusch, for
example, who has made a speciality of Merovingian hagiography) have
recently constructed, by the use of this method, precise genealogies of
the utmost solidity.[87] The results of the critical investigation of
authorship, as applied to the filiation of documents, are of two kinds.
Firstly, lost documents are reconstructed. Suppose two chroniclers, B
and C, have used, each in his own way, a common source X, which has now
disappeared. We may form an idea of X by piecing together the fragments
of it which occur imbedded in B and C, just as we form an idea of a lost
manuscript by comparing the partial copies of it which have been
preserved. On the other hand, criticism destroys the authority of a host
of "authentic" documents--that is, documents which no one suspects of
having been falsified--by showing that they are derivative, that they
are worth whatever their sources may be worth, and that, when they
embellish their sources with imaginary details and rhetorical
flourishes, they are worth just nothing at all. In Germany and England
editors of documents have introduced the excellent system of printing
borrowed passages in small characters, and original passages whose
source is unknown in larger characters. Thanks to this system it is
possible to see at a glance that celebrated chronicles, which are often
(very wrongly) quoted, are mere compilations,