INDEX LIBRORUM PROHIBITORUM  , the title of the official list of those books which on doctrinal or moral grounds the Roman Catholic Church authoritatively forbids the members of her communion to read or to possess, irrespective of works forbidden by the general rules on the subject . Most governments, whether civil or ecclesiastical, have at all times in one way or another acted on the general principle that some control may and ought to be exercised over the literature circulated among those under their jurisdiction . If we set aside the heretical books condemned by the early councils, the earliest known instance of a list of proscribed books being issued with the authority of a bishop of Rome is the Notitia librorum apocryphorum qui non recipiuntur, the first redaction of which, by Pope Gelasius (494), was subsequently amplified on several occasions . The document is for the most part an enumeration of such apocryphal works as by their titles might be supposed to be part of Holy Scripture (the " Acts " of Philip, Thomas and Peter, and the Gospels of Thaddaeus, Matthias, Peter, James the Less and other's).' Subsequent pontiffs continued to exhort the episcopate and the whole body of the faithful to be on their guard against heretical writings, whether old or new; and one of the functions of the Inquisition when it was established was to exercise a rigid censorship over books put in circulation . The majority of the condemnations were at that time of a specially theological character . With the discovery of the art of printing, and the wide and cheap diffusion of all sorts of books which ensued, the need for new precautions against heresy and immorality in literature made itself felt, and more than one pope (Sixtus IV. in 1479 and Alexander VI. in 1501) gave special directions to the archbishops of Cologne, Mainz., Trier and Magdeburg regarding the growing abuses of the printing press; in 1515 the Lateran council formulated the decree De Impressione Librorum, which required that no work should be printed without previous examination by the proper ecclesiastics' authority, the penalty of unlicensed printing being excommunication of the culprit, and confiscation and destruction of the books . The council of Trent in its fourth session, 8th April 1546, forbade the sale or possession of any anonymous religious book which had not previously been seen and approved by the ordinary; in the same year the university of Louvain, at the command of Charles V., prepared an " Index " of'pernicious and forbidden books, a second edition of which appeared in 1550 . In 1557, and again in 1559, Pope Paul IV., through the Inquisition at Rome, published what may be regarded as the first Roman Index in the modern ecclesiastical use of that term (Index auctorum et librorum qui tanquam haeretici aut suspecti aut perversi ab Officio S . R . Inquisitionis reprobantur et in universa Christiana republics interdicuntur) . In this we find the three ' Hardouin, Conc. ii . 940; Labbe, Conc. ii .

938-941 . The whole document has also been reprinted in

Smith's Dict. of Chr . •Antiq., art . " Prohibited Books."authors condemned with all their writings; prohibited books, the authors of which are known; pernicious books by anonymous authors . An excessively severe general condemnation was applied to all anonymous books published since 1519; and a list of sixty-two printers of heretical hooks was appended . This excessive rigour was mitigated in 1561 . At the 18th session of the council of Trent (26th February 1562), in consideration of the great increase in the number of suspect and pernicious books,.and also of the inefficacy of the many previous "censures " which had proceeded from the provinces and from Rome itself, eighteen fathers with a certain number of theologians were appointed to inquire into these " censures," and to consider what ought to be done in the circumstances . At the 25th session (4th December 1563) this committee of the council was reported to have completed its work, but as the subject did not seem (on account of the great number and variety of the books) to admit of being properly .discussed by the council, the result of its labours was handed over to the pope (Pius IV.) to deal with as he should think proper . In the following March accordingly were published, with papal approval, the Index librorum prohibitorum, which continued to be reprinted and brought down to date, and the " Ten Rules " which, supplemented and explained by Clement VIII., Sixtus V., Alexander VII., and finally by Benedict XIV . (loth July 1753), regulated the matter until the pontificate of Leo XIII . The business of condemning pernicious books and of correcting the Index to date has been since the time of Pope Sixtus V. in the hands of the " Congregation of the Index," which consists of several cardinals, one of whom is the prefect, and more or less numerous " consultors and " examiners of books." An attempt has been made to publish separately the Index Librorum Expurgandorum or Expurgatorius, a catalogue of the works which may be read after the deletion or amending of specified passages; but this was soon abandoned . With the alteration of social conditions, however, the Rules of Trent ceased to be entirely applicable .

Their application to publications which had no concern with morals or

religion was no longer conceivable; and, finally, the penalties called for modification . Already, at the Vatican Council, several bishops had submitted requests for a reform of the Index, but the Council was not able to deal with the question . The reform was accomplished by Leo XIII., who, on the 25th of January 1897, published the constitution Officiorum, in 49 articles . In this constitution, although the writings of heretics in support of heresy are condemned as before (No . I), those of their books which contain nothing against Catholic doctrine or which treat other subjects are permitted (Nos . 2-3) . Editions of the text of the Scriptures are permitted for purposes of study; translations of the Bible into the vulgar tongue have to be approved, while those published by non-Catholics are permitted for the use of scholars (Nos . 5-8) . Obscene books are forbidden; the classics, however, are authorized for educational purposes (Nos . 9-10) . Articles 11-14 forbid books which outrage God and sacred things, books which propagate magic and superstition, and books which are pernicious to society . The ecclesiastical laws relating to sacred images, to indulgences, and to liturgical books and books of devotion are maintained (Nos .

15-20) . Articles 21-22 condemn immoral and irreligious

newspapers, and forbid writers to contribute to them . Articles 23-26 deal with permissions to read prohibited books; these are given by the bishop in particular cases, and in the ordinary course by the Congregation of the Index. in the second part of the constitution the pope deals with the censorship of books . After indicating the official publications for which the authorization of the divers Roman congregations is required, he goes on to say that the others are amenable to the ordinary of the editor and, in the case of regulars, to their superior (Nos . 30-37) . The examination of the books is entrusted to censors, who have to study them without prejudice; if their report is favourable, the bishop gives the imprimatur (Nos . 38-40) . All books concerned with the religious sciences and with ethics are submitted to preliminary censorship, and in addition to this ecclesiastics have to obtain a personal authorization for all their books and for the acceptance of the editorship of a periodical (Nos . 41-42) . The penalty of excommunication ipso facto is only maintained for reading books written by heretics or apostates in defence of heresy, or books condemned by name under pain of excommunication by pontifical letters (not by decrees of the Index) . By the same constitution Leo XIII. ordered the revision of the catalogue of the Index . The new Index, which omits works anterior to 1600 as well as a great number of others included in the old catalogue, appeared in 19oo .

The encyclical Pascendi of Pius X . (8th

September 1907) made it obligatory for periodicals amenable to the ecclesiastical authority to be submitted to a censor, who subsequently makes useful observations . The legislation of Leo XIII. resulted in the better observance of the rules for the publication of books, but apparently did not modify the practice as regards the reading of prohibited books . It is to be regretted that the catalogue does not discriminate among the prohibited works according to the motive of their condemnation and the danger ascribed to reading them . The tendency of the practice among Catholics at large is to reduce these condemnations to the proportions of the moral law . See H . Reusch, Der Index der verbotenen Bucher (Bonn, 1883) ; A . Arndt, De Libris prohibitis commentarii (Ratisbon, 1895) ; A . Boudinhon, La Nouvelle Legislation de l'index (Paris, 1899) ; J . Hilgers, Der Index der verbotenen Bucher (Freiburg in B., 1904); A . Vermeersch, De prohibition et censura librorum (Tournai, 1907) ; T . Hurley, Commentary on the Present Index Legislation (Dublin, 1908) .

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