of his. This kind of argument
assumes that the authorship of the work we start from is undisputed;
which is practically the case with the _Ethics_ and _The Canterbury
Tales_.

But, now, granting that a work is by a good author, or contemporary with
the events recorded, or healthily related to others that were
contemporary, it remains to consider whether it has been well preserved
and is likely to retain its original sense. It is, therefore, desirable
to know the history of a book or MS., and through whose hands it has
passed. Have there been opportunities of tampering with it; and have
there been motives to do so? In reprinting books, but still more in
copying MSS., there are opportunities of omitting or interpolating
passages, or of otherwise altering the sense. In fact, slight changes
are almost sure to be made even without meaning to make them, especially
in copying MSS., through the carelessness or ignorance of transcribers.
Hence the oldest MS. is reckoned the best.

If a work contains stories that are physically impossible, it shows a
defect of judgment in the author, and decreases our confidence in his
other statements; but it does not follow that these others are to be
rejected. We must try to compare them with other evidence. Even
incredible stories are significant: they show what people were capable
of believing, and, therefore, under what conditions they reasoned and
acted. One cause of the incredibility of popular stories is the fusion
of legend with myth. A legend is a traditionary story about something
that really happened: it may have been greatly distorted by stupidity,
or exaggeration, or dramatisation, or rationalisation, but may still
retain a good deal of the original fact. A myth, however, has not
necessarily any basis of fact: it may be a sort of primitive philosophy,
an hypothesis freely invented to explain some fact in nature, such as
eclipses, or to explain some social custom whose origin is forgotten,
such as the sacrificing of a ram.

All historical conclusions, then, depend on a sum of convergent and
conflicting probabilities in the nature of circumstantial evidence. The
best testimony is only highly probable, and it is always incomplete. To
complete the picture of any past age there is no resource but the
Comparative Method. We use this method without being aware of it,
whenever we make the records of the last generation intelligible to
ourselves by our own experience. Without it nothing