Index Librorum Prohibitorum

• 1. Introduction

  ›

  The Index Librorum Prohibitorum, the Catholic Church's official list of forbidden books, ran for four centuries and eventually grew to condemn 4,000 titles. At its height, it targeted not just radical pamphleteers or anonymous heretics, but the most celebrated minds in European civilization: Galileo Galilei, René Descartes, John Locke, Immanuel Kant, Voltaire, Victor Hugo, and Jean-Paul Sartre all found their work on the list. The questions worth asking are how such a list came to exist, who actually enforced it, and why, after 406 years, it was quietly dissolved in 1966 without anyone declaring the condemned books free of error.

• 2. The Press as Threat

  ›

  Johannes Gutenberg's refinement of moveable type around 1440 transformed books from rare objects into mass-produced objects, and European governments and churches spent the next century scrambling to contain the consequences. In 1557 the English crown addressed the problem by chartering the Stationers' Company, restricting the right to print to the two universities and to 21 existing London printers, who between them operated 53 presses. France took a harder line. The printer and writer Étienne Dolet was burned at the stake for atheism in 1546. The 1557 Edict of Compiègne applied the death penalty to heretics and resulted in the burning of a noblewoman. Printers were regarded as radical by the French authorities; some 800 authors, printers, and book dealers were incarcerated in the Bastille. Early prohibition indexes had begun appearing in 1529, with Catholic Netherlands going first, followed by Venice in 1543 and Paris in 1551. By mid-century, in the tense atmosphere of the wars of religion across Germany and France, both Protestant and Catholic authorities had concluded that only a coordinated catalogue of prohibited works could stop the spread of heresy.

• 3. The First Roman Lists

  ›

  The first Roman Index was printed in 1557 under Pope Paul IV, but then withdrawn for reasons that remain unclear. A new index followed in 1559, banning the entire output of approximately 550 authors. The principle behind it was explicit: "The Pauline Index felt that the religious convictions of an author contaminated all his writing." The censors' work was considered so severe that it met resistance even within Catholic intellectual circles. After the Council of Trent authorized a revised list under Pope Pius IV, the so-called Tridentine Index was issued in 1564, and it remained the structural basis for all later editions until Pope Leo XIII published his own revision in 1897. The consequences of the Tridentine list reached well beyond theology. Protestant scholars writing on any subject were blacklisted. Obedient Catholics were denied access to the botanist Conrad Gesner's Historiae animalium, the botanical works of Otto Brunfels, the legal theory of Christoph Hegendorff and Johann Oldendorp, and the geography of Sebastian Münster. Also included was the Libri Carolini, a theological work from the 9th-century court of Charlemagne that had been published in 1549 by Bishop Jean du Tillet, and which had already appeared on two earlier prohibition lists before being folded into the Tridentine Index.

• 4. The Congregation's Machine

  ›

  In 1571, a dedicated body called the Sacred Congregation of the Index was created specifically to manage the list. It met several times a year, and between sessions each candidate work was examined by two reviewers before the congregation voted collectively on whether to include it. The pope then held final authority over any addition or removal. Condemnations were not always absolute. The congregation could attach a mitigating clause: donec corrigatur, meaning "forbidden until corrected," or donec expurgetur, meaning "forbidden until purged." This sometimes produced extensive lists of required corrections, published separately as the Index Expurgatorius. The English scholar Thomas James cited the Expurgatorius in 1627 as "an invaluable reference work to be used by the curators of the Bodleian Library when listing those works particularly worthy of collecting" -- in other words, a shopping list for a Protestant institution. The Congregation of the Index was merged with the Holy Office in 1917 under Pope Benedict XV's motu proprio Alloquentes Proxime, and from that point the Holy Office managed the Index alone.

• 5. The Twentieth Edition

  ›

  The final edition of the Index, published in 1948, contained 4,000 titles. The condemned works spanned heresy, moral deficiency, and sexual explicitness. Philosophers Schopenhauer and Nietzsche were absent, not because they were exempt but because their works were considered heretical under the existing Tridentine rule that heretical works are automatically forbidden without needing explicit listing; no separate denunciation was required. The Nazi philosopher Alfred Rosenberg's Myth of the Twentieth Century did make the list, condemned for scorning and rejecting "all dogmas of the Catholic Church, and the fundamentals of the Christian religion." More striking was what was absent: Adolf Hitler's Mein Kampf. Church historian Hubert Wolf, after gaining access to the Vatican Apostolic Archive, found that the Holy Office had studied the book for three years before deciding it should not appear on the Index, because Hitler was a head of state. The Holy Office justified the decision by citing chapter 13 of Paul the Apostle's Epistle to the Romans, regarding state authority as coming from God. The Vatican did criticize Mein Kampf in the encyclical Mit Brennender Sorge, issued in March 1937.

• 6. Enforcement and Its Limits

  ›

  The Index was directly enforceable only within the Papal States. Elsewhere it applied only if the local civil powers chose to adopt it, which happened in several Italian states. In the Holy Roman Empire, book censorship had predated the Index; it came under Jesuit control at the end of the 16th century but had limited practical effect, because German princes set up their own systems independently. France did not recognize the Church's Index at all. It was French officials who decided which books were banned, and they operated on their own criteria. Spain maintained a separate Index Librorum Prohibitorum et Expurgatorum, which largely mirrored the Roman version but added a distinct category: books that were permitted once a forbidden passage, sometimes a single sentence, was physically removed or "expurgated." Cardinal Ottaviani acknowledged in April 1966 that the Congregation for the Doctrine of the Faith could not keep up with the volume of contemporary literature, a candid admission that the enforcement mechanism had lost its practical grip long before the formal dissolution.

• 7. The First Woman Listed

  ›

  Magdalena Haymairus became the first woman placed on the Index in 1569, listed for a children's book titled Die sontegliche Episteln über das gantze Jar in gesangsweis gestellt, a collection of Sunday Epistles put into hymns. Other women who appeared on the Index over the centuries included Anne Askew, Olympia Fulvia Morata, Ursula of Munsterberg, who lived from 1491 to 1534, Veronica Franco, and Paola Antonia Negri, who lived from 1508 to 1555. The Index's treatment of individual authors could also shift with time. Writings by the philosopher Antonio Rosmini-Serbati were placed on the Index in 1849 but removed by 1855. Pope John Paul II later cited Rosmini's work as a significant example of philosophical inquiry enriched by engaging the data of faith. Contrary to a widely held belief, the works of Charles Darwin were never included in the Index at any stage.

• 8. Dissolution and Its Aftermath

  ›

  On the 7th of December 1965, Pope Paul VI issued the motu proprio Integrae servandae, reorganizing the Holy Office as the Sacred Congregation for the Doctrine of the Faith. The Index was not listed among the new body's responsibilities, prompting immediate questions about its status. Cardinal Alfredo Ottaviani, pro-prefect of the congregation, confirmed that it was no longer in force. A June 1966 notification from the congregation stated that the Index retained its "moral force" in that it taught Christians to beware of writings that could endanger faith and morals, but it no longer carried the force of ecclesiastical positive law with associated penalties. The obligation, in other words, was transferred from law to conscience. In a letter dated the 31st of January 1985, Cardinal Joseph Ratzinger, then Prefect of the Congregation and later Pope Benedict XVI, reinforced this position by noting that a decision against a condemned work could be reversed, but "only after profound changes that neutralize the harm which such a publication could bring forth among the ordinary faithful." The 1758 edition had already removed the general prohibition against works advocating heliocentrism as fact rather than hypothesis, a small but telling adjustment: two Franciscan mathematicians had published an edition of Isaac Newton's Principia Mathematica in 1742, sixteen years earlier, with a preface conceding that the work assumed heliocentrism and could not be explained without it.