A list of books which are prohibited reading for members of the Roman Catholic Church. This practice is in keeping with a tradition which regards certain works as dangerous to the faith and morals of Catholics. Under Pope Gelasius I (492-96) a decree was issued which divided books into three categories: authentic scriptural ones, recommended works, and heretical works. Many specific works were denounced until the formal codification of forbidden books took place under Paul IV (1555-59). One of the tasks of the Congregation of the Inquisition was to compile a catalog of forbidden books, and this was published with papal approval in 1559, the first such list to bear the official title of “Index.”
Due to dissatisfaction with this Index the leaders of the Council of Trent (1545-63) began a revision, but were unable to complete it and appointed a commission for this purpose. As a result the Tridentine Index or Index of Pope Pius IV (1559-65) was issued in 1564. In addition to the list of forbidden books, it contained ten guidelines for regulating censorship. Revisions of the Index include those of Sixtus V (1590), Clement VIII (1596), Alexander VII (1664), Benedict XIV (1751), and Leo XIII (1897 and 1900). The last revision of the Leonine Index took place in 1948. In 1966 at Vatican Council II,* it was declared that no further editions of the Index would be issued, and its chief value today is historical. Catholics are still, however, bound to abide by certain guidelines prohibiting the reading of books which constitute a possible spiritual danger.
See also R.A. Burke, What Is the Index? (1952); and H.C. Gardiner, Catholic Viewpoint on Censorship (1958; rev. ed., 1961).