“Of the duties and obligations which ought to be most carefully and faithfully performed in this Apostolic Office, this is the chief and most important matter, namely,--to watch zealously and make every effort that the integrity of the faith and morals of Christians shall not be impaired. If this were ever necessary, it is especially so in this age--when, in the midst of unbounded license of character and morals, almost all the teaching which Jesus Christ, the Saviour of Mankind, entrusted to the care of his Church for the salvation of the human race is attacked, with daily criticism and discussion. “In this criticism, our opponents use various and innumerable stratagems and artifices for the purpose of causing injury; but especially dangerous is the lack of moderation in their writings and the influence of these pernicious writings among the people. For nothing worse can be imagined for contaminating the minds of men, both by making them despise religion and by suggesting many incentives to sin. Wherefore the Church, the guardian and protector of the integrity of faith and morals, in fear of this great evil, long ago came to the conclusion that measures must be adopted to guard against the danger. To this end, it made continued efforts to prohibit men, as far as practicable, from the reading of pernicious books, which are the worst kind of poison. Even the very remote age of St. Paul saw an eager zeal in this matter. And in like manner, every subsequent generation has witnessed the watchful care of the holy Fathers, the instructions of the bishops, and the decrees of the Church councils. “Especially do the records of literature bear witness to the care and diligence shown by the Roman pontiffs to prevent the writings of heretics, a constant menace to the community, from making their way unnoticed into circulation. The earlier years are full of examples of this. Anastasius I condemned by a solemn edict the more dangerous writings of Origen; Innocent I did the same with all the works of Pelagius, and Leo the Great with those of the Manichaeans. There are known to be decretal letters about the same matter concerning the acceptance and the non-acceptance of certain books. For one of these letters Gelasius is responsible. Likewise, in the course of years, the decree of the Holy See has condemned the pestilent books of the Monothelites, of Abélard, Marsilius of Padua, of Wyclif, and of Huss.