Chapter X — On prohibited Books

I. The prohibition of books is ancient, and is found in Acts chapter 19: And many of them who had followed curious arts, brought together their books, and burnt them before all. The Council of Nicaea commanded the books of Arius to be burned, as Socrates narrates, book 1, chapter 6.

II. For a twofold reason the books of Heretics are prohibited: both that the evil of seduction may be impeded, and that the Heretics may be confounded. Heretical books are proscribed in the Bull Coenae. Under this prohibition are not comprehended the books of the Jews, of the Mahometans, or of the Heathen. This prohibition has annexed to it the penalty of excommunication when four conditions concur: 1. That the books be those of Heretics. 2. That they teach Heresy, or treat of Religion. 3. That they be knowingly read, retained, or printed. 4. That this be done without the authority of the supreme Pontiff. Those books treat of Religion which expound sacred Scripture and Theology; which interpret the affairs of Monks, of Clerics, the worship of the Saints, and rites; but not those which handle philosophical and historical matters and other inferior arts.

III. He who reads a book of a catholic author in which the errors of the Heretics were described is not subject to the penalties of the Bull, because the book is not a Heretic's, but a Catholic's. The same must be said of one reading a book of a catholic author in which certain heresies were written through ignorance. Nor does it matter whether the books of Heretics are written by pen or published in type. He who reads a sermon, an oration, an epistle, or a disputation of a Heretic containing heresy is subject to the penalties of the Bull — whatever Sanchez teaches to the contrary. Wherefore the opinion of Fr. Sporer is not to be admitted, who with Sanchez, Laymann, and others teaches that he does not incur the excommunication who should read a writing of a Heretic of fewer than ten leaves. There is, however, a parvity of matter in this reading. What is it? Azor assigns one or two little verses; Suarez, two or three lines; Sanchez, a page of a leaf; Fagundez assigns a page and a half; and each speaks according to his own pleasure. A certain rule cannot be designated. Deliberate reading is not free of venial fault. Wherefore the one safe way is to abstain altogether from this reading. Yet the circumstances of the person reading, of the thing read, and other things of this kind must be regarded, that the gravity of the fault may be defined.

IV. He who reads a book of a Heretic which in no way treats of Religion is not subject to the penalties enacted in the Bull Coenae. Yet the books of the Heresiarchs — of Luther, of Calvin, and of the others — are all forbidden, in whatever matter.

V. That anyone may incur the penalties contained in the Bull, he must read knowingly; that is, knowledge is required both of the law and of the fact: he must know both that the reading of a heretical book is forbidden, and that the book which he reads is heretical. To the same penalties is subject he who hands a heretical book to another to be read, that he may hear the reader. But he who by fortuitous chance hears another reading is not subject to the penalties contained in the Bull, but can sin more or less according to the diversity of circumstances. A Theologian, a Preacher, a Confessor, when grave necessity presses, can read the books of the Heretics, either to confound the Heretics or to confirm the Catholics. Yet this rarely happens.

VI. Those who have obtained a license, either from the supreme Pontiff or from the Congregation of the Holy Office, to read heretical books, if they suffer danger of seduction, and feel their mind shaken by grave temptations, sin mortally in reading such books. For no pontifical license can free from the duty of avoiding an occasion that gravely allures. But those who suffer no temptation do not sin gravely, even if they read from mere curiosity. Not only do they sin gravely who without legitimate faculty read heretical books, and incur the reserved excommunication; but also those who retain them for any cause whatsoever, whether for show and ornament, or to fill their libraries.

VII. Printers of heretical books sin mortally, and contract the excommunication — as do all those who lend helping hands to the printers, who hand over the book to be printed, who furnish inks or types: because all contribute to the printing, and favor the Heretics.

VIII. In the Tridentine and Roman Index, besides the books of the Heresiarchs, many books of Catholics are prohibited. The former are named of the first class, the latter of the second. Those books of Catholics are prohibited which contain errors hostile to the doctrine of faith or of morals, or which instill a suspicion of error, or offend pious ears, or furnish scandal, or contain lax opinions. Books of this class are sometimes prohibited until they be corrected. This happens when in the book absolutely sound doctrine is contained, but some proposition, which is not capital, has fallen from the author's pen beside his intention, or from a slip of the mind, or through ignorance. Such books are prohibited under mortal sin, and an excommunication not reserved.

IX. There are several other kinds of books prohibited in the aforesaid Index. First, all books treating of Magic. Secondly, books of astrology. Thirdly, all obscene books are prohibited by the law itself; nor does any faculty or license avail for the reading of these, for they are by their nature pestilential. Finally, in the fourth rule of the Roman Index the reading of the sacred Bible in the vernacular tongue is forbidden without the license of Superiors. A book proscribed in one language is proscribed in every other, unless there be a difference, and a correction have been made.