# Canons and Decrees of the Council of Trent/Second Part/The Bull of our Holy Lord Pius IV.

Incipit: Dominici gregis custodiae
THE BULL OF OUR HOLY LORD PIUS IV., BY DIVINE PROVIDENCE POPE.
APPROBATION OF THE INDEX OF PROHIBITED BOOKS, WITH THE RULES CONFIRMED BY THE FATHERS DEPUTED BY THE HOLY COUNCIL OF TRENT, AND THE PROHIBITION TO KEEP OR READ THESE BOOKS.
Pius IV., pope, for the future memory hereof.
Appointed over the protecting the Lord's flock by the disposition of the Lord, like unto a wakeful shepherd, we ​cease not to guard the flock itself with the utmost care and diligence from imminent dangers, lest through our negligence the sheep may perish, which were redeemed by the most precious blood of our Lord Jesus Christ. But although those matters which appertain to lay open the truth of faith and to confute the heresies of modern times were so enucleated and defined in the œcumenical and general Council of Trent, by the influence of the grace of the Holy Ghost, that it is now easy for each person to distinguish sound and Catholic doctrine from that which is false and spurious; yet, whereas the reading of books published by heretics is wont not only to corrupt mere simple men, but also to lead learned and erudite men into various errors and opinions, foreign to the truth of the Catholic faith, for this matter, also, we deemed it necessary to provide.
But, knowing that the fittest remedy for that evil was, if an index or catalogue of the books which are either heretical, or suspected of heretical depravity, or at least, are injurious to morals and piety, were drawn up and published, we referred that matter to the sacred Synod of Trent: this [synod], out of so great a number of bishops and other most earned men, chose for drawing up that index many prelates distinguished as well for learning as judgment, from nearly all nations. They, indeed, perfected that index by God's help, not without the greatest labour and much watching; certain most distinguished theologians also being called in to the council. But, the council being over, when, in pursuance of the decree of the synod itself, that index had been presented to us, so that it should not be published before it had been approved by us, we delivered it to certain most learned and approved prelates, to be read over most carefully, and to be examined, and we ourselves read it.
When, therefore, we had ascertained that it had been drawn up with great study, keen judgment, and long care, and besides, most conveniently digested; we, desiring to consult for the salvation of souls, and for that reason to take care that no books and writings of any kind, which are disapproved in it either as heretical, or as suspected of heretical depravity, or as detrimental to piety and purity of morals, or at least, as requiring any correction, should ​after be read by the faithful in Christ, by our apostdic anthority do approve by these presents the index itself, together with the rules prefixed to it, and we command and decree that it be printed and published, and that it be received everywhere by all Catholic universities and all others soever, and that these rules be observed; prohibiting all and every one, as well ecclesiastical persons, secular and regular, of what we order, or dignity soever they may be. as lay persons endowed with any honour and dignity soever, that no one should dare to read or keep any books contrary to the prescriptions of these rules, and the prohibition of the index itself.
But if any one shall act in opposition to these rules and Prohibition, he, indeed, who shall read or keep the books of heretics, or the writings of any author condemned and prohibited on account of heresy or the suspicion of false dogma, shall, by the very feet, fall under the penalty of excommunication, and for that reason it may be lawful to inquire into, and proceed against him as one suspected of heresy, besides the other penalties appointed for this by the Apostolic See and the sacred canons. But let him who shall read or keep books prohibited for any other cause besides the guilt of deadly sin, know that ne is to be severely punished at the discretion of the bishops; notwithstanding any constitutions and ordinances soever to the contrary; or if an indult has been granted to any collectively or separately by the same see, so that they may not be excommunicated by apostolic letters, not making full and express and word for word mention of such indult.
But that these things may come to the knowledge of all men, and that no one may be able to make use of the plea of ignorance, we will and command, that these letters be read out openly and with a loud voice by some ushers of our court in the Vatican Basilica of the prince of the apostles, and in the Lateran church, at the time when the people is wont to be assembled therein, in order to be present at the solemn sacrifice of the masses, and after they have been read out, they be affixed to the doors of these churches, and also of those of the apostolic chancery, and in the usual place of the Campo di Piore, and let them be left there for some time, that they may be read and become known to all. But ​when they shall be removed thence, let copies of them remain affixed in the same places. But by this reading, publication, and affixing, we will that each and every person included in these letters, in three months, to be reckoned from the day of its publication and affixion, be [thereby] bound and obliged in the same manner as if they had been published and read out to themselves. To copies also of it, which copies have been written, subscribed by the hand of some public notary, and vouched for by the seal and subscription of some person constituted in ecclesiastical dignity, we command and decree that credit be attached without any doubt.
Given at Rome, at St. Peter's, under the seal of the Fisherman, on the 24th day of March, 1564, the fifth year of our pontificate.
Antoninus Florabellus Lavellinus