The Index Librorum Prohibitorum (List of Prohibited Books)—also called Index Expurgatorius—is a list of publications which Roman Catholics were banned from reading, "pernicious books", and also the rules of the Church relating to books. The aim of the list was to prevent the reading of immoral books or works containing theological errors and so prevent the corruption of the faithful.

It was created in 1559 by the Sacred Congregation of the Inquisition of the Roman Catholic Church (later the Congregation for the Doctrine of the Faith). The index was regularly updated until the 1948 edition, with materials being added by either the Congregation or the Pope. The list was not simply a reactive work; the authors were encouraged to defend their works, they could re-publish with elisions if they wished to avoid a ban, and pre-publication censorship was encouraged.

The 32nd edition, published in 1948, contained 4,000 titles censored for various reasons: heresy, moral deficiency, sexual explicitness, political incorrectness, and so on. Notable writers on the list were Laurence Sterne, Voltaire, Daniel Defoe, Nicolaus Copernicus, Honoré de Balzac, Jean-Paul Sartre, as well as the Dutch sexologist Theodor Hendrik van de Velde, author of the sex manual The Perfect Marriage .

Some of the Index's actions were of a definite political content: in 1926, the Action Française magazine, espousing far-right French causes, was put in the Index.

The Index's effects were felt throughout much of the Catholic world. For many years in areas as diverse as Quebec and Poland it was very difficult to find copies of indexed works, especially outside of major cities. The index as an official list was relaxed in 1966 under Pope Paul VI following the end of the Second Vatican Council and largely due to practical considerations. It remains a sin for Catholics to read books which are injurious to faith and/or morals.

See also

• Banned books
• Censorship

External links

• Contemporary Catholic's dilemma
• Facsimile of the 1559 index
• List of famous authors in the index
• "Index of Prohibited Books", The Catholic Encyclopedia, 1913: "The first Roman Index of Prohibited Books (Index librorum prohibitorum), published in 1559 under Paul IV, was very severe, and was therefore mitigated under that pontiff by decree of the Holy Office of 14 June of the same year. It was only in 1909 that this Moderatio Indicis librorum prohibitorum (Mitigation of the Index of Prohibited Books) was rediscovered in "Codex Vaticanus lat. 3958, fol. 74", and was published for the first time." The effectiveness of such a mitigation is open to question.