Index Librorum Prohibitorum

The Index Librorum Prohibitorum (English: List of Prohibited Books) was a list of publications prohibited by the Catholic Church. A first version (the Pauline Index) was promulgated by Pope Paul IV in 1559, and a revised and somewhat relaxed form (the Tridentine Index) was authorized at the Council of Trent. The promulgation of the Index marked the "turning-point in the freedom of enquiry" in the Catholic world. The final (20th) edition appeared in 1948, and it was formally abolished on 14 June 1966 by Pope Paul VI.

The avowed aim of the list was to protect the faith and morals of the faithful by preventing the reading of immoral books or works containing theological errors. Books thought to contain such errors included some scientific works by leading astronomers such as Johannes Kepler's Epitome astronomiae Copernicianae, which was on the Index from 1621 to 1835. The various editions of the Index also contained the rules of the Church relating to the reading, selling and pre-emptive censorship of books, including translations of the Bible into the "common tongues".

Canon law still recommends that works concerning sacred Scripture, theology, canon law, church history, and any writings which specially concern religion or good morals, be submitted to the judgment of the local Ordinary. The local Ordinary consults someone whom he considers competent to give a judgment and, if that person gives the nihil obstat ("nothing forbids") the local Ordinary grants the imprimatur ("let it be printed"). Members of religious institutes require the imprimi potest (it can be printed) of their major superior to publish books on matters of religion or morals.

Some of the scientific works that were on early editions of the Index (e.g. on heliocentrism) have long been routinely taught at Catholic universities worldwide. Giordano Bruno, whose entire works were placed on the Index on 8 February 1600 was burned alive at the stake (albeit after being turned over to the secular authorities for teaching the heresy of pantheism, not for heliocentrism or other scientific views). In 2002, a retired Roman Catholic bishop gave his personal approval to the writings of Maria Valtorta, which had been on the Index (though never in a printed edition) and which have still not been given official Church approval. Mary Faustina Kowalska, whose writings were likewise forbidden, was canonized in 2000, and Antonio Rosmini-Serbati, one of whose works was on the Index, was beatified in 2007. The developments since the abolition of the Index signify "the loss of relevance of the Index in the 21st century."