“But in the 15th century, with the invention of the new art of printing, not only were prohibitions made against wicked books that had actually appeared, but efforts were also made to prevent the publication of any further such books. This foresight was demanded for that age not on any trivial grounds, but by the necessity for the preservation of the public integrity and safety; because an art, most excellent in itself, and the source of very great advantages, which had come into existence originally for the purpose of propagating Christian civilisation, had been speedily perverted by the action of many into a powerful instrument of evil. The great and pernicious influence of wicked writers had more serious and more rapid results because of this very increase in the extent of the circulation of literature. Therefore, by a most wise policy, both Alexander VI and Leo X, my predecessors, made regulations, adapted to the character of the times, to keep publishers in the path of duty. “Later, as the evil was recognised as more serious, it became necessary to use strict and more strenuous measures to check the contagious spread of wicked heresies. To this end, the same Leo X, and afterwards Clement VII, positively forbade any one to read or to possess the books of Luther. But when, in accordance with the calamities of the age, the foul collection of dangerous books had increased beyond all bounds and had penetrated in every direction, the need of a more far-reaching and more immediate remedy was recognised. This remedy was first opportunely suggested by our predecessor Paul IV, namely, the publication of a list of writers and books, from the perusal of which the faithful were to abstain. Not long afterwards, the Fathers of the Synod of Trent took further measures for checking the increasing license of writing and of reading. In accordance with their wish and instructions, directors and theologians chosen for this purpose took great pains not only in amplifying and perfecting the Index which Paul IV had published, but also in framing rules to be observed in the publishing, reading, and possessing of books. To these rules, Pius IV added the weight of the Apostolic authority. “But the needs of the public welfare, which in the beginning had caused to be framed the Rules of Trent, promulgated from the council, came in later years to call for further action. Therefore, the Roman pontiffs, and especially Clement VIII, Alexander VII, and Benedict XIV, with full understanding of the requirements and with thoughtful discretion, framed further decrees to explain these rules and to adapt their instruction to the later generations.