The most common manuscripts of the time, which had hitherto been the cheapest mode of intellectual communication, were especially fitted to be reproduced by the new art; they were those illustrated abridgments of Scriptural history or doctrine, called _Biblia Pauperum_, or books of the poor preachers, which had long been used in popular religious instruction, in accordance with the mediæval custom of conveying religious ideas to the illiterate more quickly and vividly through pictures than was possible by the use of language alone. In the sixth century Gregory the Great had defended wall-paintings in the churches as a means of religious instruction for the ignorant population which then filled the Roman provinces. In a letter to the Bishop of Marseilles, who had shown indiscreet zeal in destroying the pictures of the saints, he wrote: “What writing is to those who read, that a picture is to those who have only eyes; because, however ignorant they are, they see their duty in a picture, and there, although they have not learned their letters, they read; wherefore, for the people especially, painting stands in the place of literature.”[27] In conformity with this opinion these manuscripts were composed at an early period; they were written rapidly by the scribes, and illustrated with designs made with the pen, and rudely colored by the rubricators. They served equally to take the place of the Bible among the poor clergy--for a complete manuscript of the Scriptures was far too valuable a treasure to be within their reach--and to aid the people in understanding what was told them; for, doubtless, in teaching both young and old the monks showed these pictures to explain their words, and to make a more lasting impression upon the memory of their hearers. These designs, it is worth while to point out, exhibit the immobility of mind in the mediæval communities, guided, as they were, almost wholly by custom and tradition; the designs were not original, but were copied from the artistic representations in the principal churches, where the common people may have seen them, when upon a pilgrimage or at other times, carved among the bass-reliefs or glowing in the bright colors of the painted windows. They were copied without change, the scenes were conceived in the same manner, the characters were represented after the same conventional type, even in the details there was slight variation; and as the decorative arts in the churches were subordinated to architecture, these designs not infrequently bear the stamp of their original purpose, and are marked by the characteristics of mural art. They were copied, too, not only by the scribes from early representations, but they were reproduced by the great masters of the Renaissance from the manuscripts and block-books themselves; Dürer, Quentin Matzys, Lukas van Leyden, Martin Schön, and, in earlier times, Taddeo Gaddi and Orcagna, took their conceptions from these sources.