understand the conditions
under which mediaeval scholars worked, it is of the utmost importance
to realize this state of uncertainty and flux.

Not that in manuscript days there was indifference to accuracy.
Serious scholars and copyists laid great stress upon it. With
insistent fervour they implored one another to be careful, and to
collate what had been copied. But there are limits to human powers.
Collation is a dull business; and unless done with minute attention,
cannot be expected to yield perfect correctness. When a man has copied
a work of any length, it is hard for him to collate it with the
original slowly. Physically, of course, he easily might: but the
spirit is weak, and, weary of the ground already traversed once, urges
him to hurry forward, with the inevitable result.

With a manuscript, too, the possible reward might well seem scarcely
worth the labour; for how could any permanence be ensured for critical
work? A scholar might expend his efforts over a corrupt author, might
compare his own manuscript with others far and near, and at length
arrive at a text really more correct. And yet what hope had he that
his labour was not lost? His manuscript would pass at his death into
other hands and might easily be overlooked and even perish. Like a
child's castle built upon the sand, his work would be overwhelmed by
the rising tide of oblivion. Such conditions are disheartening.

Thus mediaeval standards of accuracy were of necessity low. In default
of good instruments we content ourselves with those we have. To draw a
line straight we use a ruler; but if one is not to be had, the edge of
a book or a table may supply its place. In the last resort we draw
roughly by hand, but with no illusions as to our success. So it was
with the scholar of the Middle Ages. His instruments were imperfect;
and he acquiesced in the best standards he could get: realizing no
doubt their defects, but knowing no better way.

But with printing the position was at once changed. When the type had
been set up, it was possible to strike off a thousand copies of a
book, each of which was identical with all the rest. It became worth
while to spend abundant pains over seeking a good text and correcting
the proofs--though this latter point was not perceived at first--when
there was the assured prospect of such uniformity to follow. One
edition could be distinguished from another by the dates on title-page
and colophon; and work once done wa