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 was done for all time, if enough copies of a book were taken off. This necessarily produced a great change in methods of study. Instead of a single manuscript, in places perhaps hopelessly entangled, and always at the mercy of another manuscript of equal or greater authority that might appear from the blue with different readings, the scholar received a text which represented a recension of, it may be, several manuscripts, and whose roughnesses had been smoothed out by the care of editors more or less competent. The precious volumes to which modern book-lovers reverently give the title of 'Editio princeps', had almost as great honour in their own day, before the credit of priority and antiquity had come to them; for in them men saw the creation of a series of 'standard texts', norms to which, until they were superseded, all future work upon the same ground could be referred. As a result, too, of the improved correctness of the texts, instead of being satisfied with the general sense of an author, men were able to base edifices of precise argument upon the verbal meaning of passages, in some confidence that their structures would not be overset.