I am merely seeking validation, or otherwise, on an article appearing on Reddit/Ask Historians, regarding the 'Index Librorum Prohibitorum'.

This came to attention recently as Elon Musk has called for a 'Moratorium' on research into Artificial Intelligence and some have likened this step to a similar, supposed, historical event.

Is this article factual, or not ? Did the Roman Catholic Church seek to prohibit the publication of Protestant literature, by influencing University and Government powers in the late fifteenth and early sixteenth centuries ?

When the Catholic Church realised that the printing press was being used to proliferate Protestant literature, their response wasn't to ban the printing press, it was to ban printers from publishing heretical texts. Their response to this new technology was not to ban the technology, it was to ban the use of the technology for - in their view - nefarious and dangerous purposes. Local governments and the church would issue an Index Librorum Prohibitorum (Index of Prohibited Books) that publishers were not allowed to print. For example, King Henry II of France issued the Edict of Châteaubriant in 1551 to suppress Protestantism, and among its terms were that publishers had to adhere to the Index Librorum Prohibitorum maintained by the faculty of the University of Paris, and the University of Paris was permitted to inspect publishers twice a year to check for breaches of the Index Librorum Prohibitorum. They had nothing against the printing press itself - they were happy to use it to proliferate their own literature - but they took issue with what it was being used for.

Chartier, Roger, ed. The Culture of Print: Power and the Uses of Print in Early Modern Europe. Princeton University Press, 2014.

Meserve, Margaret. "The Papacy, Power, and Print: The Publication of Papal Decrees in the First Fifty Years of Printing." Print and Power in Early Modern Europe (1500–1800). Brill, 2021. 259-299.

Sachet, Paolo. Publishing for the Popes: The Cultural Policy of the Catholic Church towards Printing in Sixteenth-Century Rome. PhD Diss. University of London, 2015.

Reddit - Ask Historians - Catholic Church : "6 month Moratorium"

It would seem to me that, if this is historically true, then it says a lot about the development of the Roman Catholic Church in history if, at that time, as is alleged, it deliberately aligned itself with government and academia to censor the conscientious exposition of scripture towards a true apprehension of God through his Son, Jesus Christ.

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    Government and academia (which was mostly theology) had been involved in the pursuit of heresy (as defined by the church at the time) since the time of Constantine; which makes your question a rather big subject. I suggest reading a biography of Wycliffe, Luther, or any of the Reformers. Apr 11, 2023 at 6:08
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    @StephenDisraeli Been there. Done that. (Approximately half a century ago : ) What it indicates is that Protestants (at the time) quite rightly discerned where and what was the 'false' prophet' and the 'antichrist' in their own day, which joined religion to 'learning' and to politics against the true movings of the Spirit in accordance with the Word of God.
    – Nigel J
    Apr 11, 2023 at 10:33
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    CATHOLIC ENCYCLOPEDIA: Index of Prohibited Books is quite open about their history of censorship.¶ List of authors and works on the Index Librorum Prohibitorum - Wikipedia is quite interesting (e.g. "Les Misérables" was banned until 1959). Apr 11, 2023 at 13:03
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    @User14 It is not doctrinal, agreed. But it is a matter of comparative Christianity.
    – Nigel J
    Apr 11, 2023 at 15:58
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    "then it says a lot about the development of the Roman Catholic Church" only from a Protestant/liberalism perspective. That is, if Protestantism is true, then Catholicism at that time acted against the truth. This doesn't necessarily follow if Catholicism is in fact true.
    – eques
    Apr 11, 2023 at 21:35

2 Answers 2


The simple answer is, "Yes, it did", and already a list of official Catholic quotations have been given to show this, with the offer to provide many more.

Of note is that the background to Catholic bans of the 16th century shows a predating of similar attempts before moveable type first started to be used in the 11th century in China. Europe caught up three centuries later. The question is only concerned with what happened from the late 15th century into the 16th, however. This is just to point out a consistent "hard line" by catholicism from the early fifteenth century to burn Bible manuscript translations into languages other than Old Latin, and to prevent printing of, or to ensure destruction of already printed Bibles in languages other than the 'approved' one. (As non-Catholic production of Bibles was a main part of the literature they produced, the Bible has to be included in this consideration.)

A law was enacted in 1401 to burn ‘heretics’. After the burning to death of Sir John Oldcastle, a law was passed that whoever read the Scriptures in English should forfeit land, chattels, goods and life, and be condemned as a heretic to God, an enemy to the crown, and a traitor to the kingdom. In 1407 Thomas Arundel, Archbishop of Canterbury, decreed, "We therefore legislate and ordain that nobody from this day forth translate any text of Holy Scripture on his own authority into English." Even as late as 1513, the Dean of St. Paul's cathedral was suspended just for translating the Lord's Prayer into English.

Jan Huss of Prague was confessor to the Queen of Bohemia. He became a Protestant Reformer. The pope excommunicated Huss and had Wycliffe’s writings publicly burned despite the king of Bohemia, the nobility, the University and the majority of the people supporting Huss and his teaching. This is related to the question as it shows Catholicism over-riding objections to such treatment by the king, the nobility and the university at that time. Such objections from such quarters seem to have been stifled.

At Constance a Council was opened in 1414, which lasted three and a half years. One of its tasks was to combat the teachings associated with Wycliff and Huss. Huss was invited to attend and Emperor Sigismund assured him of safe conduct. Despite the Imperial promise, he was seized and cast into a foul dungeon on an island in lake Constance. To justify this, the Council issued a decree in 1415 that a decision given by the Holy Spirit is infallible and forever binding, so that the church is not bound to keep faith with a heretic. Every effort was made to get Huss to recant his belief that salvation is by grace, through faith, and apart from works of law. He was willing to recant anything he had taught which could be shown from Holy Scripture to be wrong, though he would withdraw nothing that he saw to be taught in the Word of God. He was burned to death for that. It wasn’t just due to preaching from a disapproved translation of the Bible. He could have preached the same doctrines of grace from any Bible, in any language that he could read (and he could read Latin). It was WHAT he taught from the Scriptures that got him burned. In 1480 the Catholic monarchs Ferdinand and Isabella made the Spanish Inquisition a royal instrument with its centre at Madrid.

That predates the 1520 decrees already quoted in an answer here but helps to understand what led up to the era in question. The Index Librorum Prohibitorum list of prohibited books started in 1559 during the Council of Trent was not closed until 1966.

That last point bringing us into the 20th century, it may be worth giving a bit more attention to a previously posted quote of Pope Pius XI in Allocution, December 20, 1926: “Catholics may not support, favor, or read papers which are edited by men whose writings are in notable opposition to Catholic doctrine in faith and morals...”

There was a BBC news item last night where the matter of specially trained editors going through modern books to change "politically incorrect" language that would upset people in certain groups had a promoter explain why this was a jolly good idea. Then an academic spoke in warning of this censorship now manifesting in Britain. It might only be a question of time before the Bible, and Bible-supporting literature, receives such "politically correct" censorship, this time from mainly non-religious sources. Everything I've found on this matter of Catholic banning of Protestant literature, including the Bible, confirms the quotes you give.


It has always been the Church's policy to extirpate heresy.

Pope Pius VIII, Traditi Humilitati, 1829: “The heretics have disseminated pestilential books everywhere, by which the teachings of the impious spread, much as a cancer. To counteract this most deadly pest, spare no labor.”

This was also practised against Luther and other Protestant heretics.

Pope Leo X, Exsurge Domine, 1520: “Moreover, because the preceding errors and many others are contained in the books or writings of Martin Luther, we likewise condemn, reprobate, and reject completely the books and all the writings and sermons of the said Martin, whether in Latin or any other language, containing the said errors or any one of them; and we wish them to be regarded as utterly condemned, reprobated, and rejected. We forbid each and every one of the faithful of either sex, in virtue of holy obedience and under the above penalties to be incurred automatically, to read, assert, preach, praise, print, publish, or defend them. They will incur these penalties if they presume to uphold them in any way, personally or through another or others, directly or indirectly, tacitly or explicitly, publicly or occultly, either in their own homes or in other public or private places. Indeed immediately after the publication of this letter these works, wherever they may be, shall be sought out carefully by the ordinaries and others [ecclesiastics and regulars], and under each and every one of the above penalties shall be burned publicly and solemnly in the presence of the clerics and people.”

And it didn't stop at burning books...

Pope Leo X, Exsurge Domine, 1520, ex cathedra: “Some of these errors we have decided to include in the present document; their substance is as follows: ...33. That heretics be burned is against the will of the Spirit. ...No one of sound mind is ignorant how destructive, pernicious, scandalous, and seductive to pious and simple minds these various errors are, how opposed they are to all charity and reverence for the holy Roman Church who is the mother of all the faithful and teacher of the faith; how destructive they are of the vigor of ecclesiastical discipline, namely obedience. This virtue is the font and origin of all virtues and without it anyone is readily convicted of being unfaithful.”

Many who call themselves Catholics recoil at the teaching of the Church on burning heretics, however, that is because they are not looking with the eyes of faith but are as godless men who perceive only the corporal.

Consider that a murderer deserves death for sowing death, but how much more serious is the destruction of souls compared to the body?

St. Jerome, Homilies on the Psalms: “The doer of evil has, indeed, killed his own soul; but the heretic — the liar — has killed as many souls as he has seduced... Every heretic is bloodthirsty, for every day he spills the blood of souls.”

St. Thomas Aquinas, Summa theologiae II-II, q. 11. a. 3: “Therefore if forgers of money and other evil-doers are forthwith condemned to death by the secular authority, much more reason is there for heretics, as soon as they are convicted of heresy, to be not only excommunicated but even put to death.”

St. Peter Canisius, doctor of the Church, admonishes rulers for not fulfilling their duty of administering justice and protecting the people with the sword.

“Herein magistrates offend, when they bear the sword in vain, and are not, as they are called, God’s ministers and revengers unto wrath, to those that behave themselves wickedly or seditiously.”

Nevertheless, the Holy Roman and Universal Inquisiton of the Holy Office was quite lenient for it never condemned anyone as a heretic unless he admitted to being one. The liar Galileo escaped death by concealing his heresy and was therefore branded vehemently suspect of heresy.

Pope Pius IX tackles the root of the error of freedom of the press and condemns the Second Vatican Council with his apostolic authority a century in advance.

Pope Pius IX, Quanta Cura (#’s 3-6), Dec. 8, 1864, ex cathedra: “From which totally false idea of social government they do not fear to foster that erroneous opinion, most fatal in its effects on the Catholic Church and the salvation of souls, called by Our predecessor, Gregory XVI, an INSANITY, namely, THAT ‘LIBERTY OF CONSCIENCE AND WORSHIP IS EACH MAN’S PERSONAL RIGHT, which ough to be legally proclaimed and asserted in every rightly constituted society; and that a right resides in the citizens to an absolute liberty, which should be restrained by no authority whether ecclesiastical or civil, **whereby they may be able openly and publicly to manifest and declare any of their ideas whatever, either by word of mouth, by the press, or in any other way. But while they rashly affirm this, they do not understand and note that they are preaching liberty of perdition… Therefore, BY OUR APOSTOLIC AUTHORITY, WE REPROBATE, PROSCRIBE, AND CONDEMN ALL THE SINGULAR AND EVIL OPINIONS AND DOCTRINES SPECIALLY MENTIONED IN THIS LETTER, AND WILL AND COMMAND THAT THEY BE THOROUGHLY HELD BY ALL THE CHILDREN OF THE CATHOLIC CHURCH AS REPROBATED, PROSCRIBED AND CONDEMNED.” (Denz. 1690; 1699)

Statements to a similar effect are almost countless, here is one more:

Pope Pius XI, Allocution, December 20, 1926: “Catholics may not support, favor, or read papers which are edited by men whose writings are in notable opposition to Catholic doctrine in faith and morals...”

I also recommend all Protestants read Exsurge Domine and consider how merciful the Church was to Luther despite the enormous evil he was doing.

  • "that is because they are not looking with the eyes of faith but are as godless men who perceive only the corporal." Or because they understand Romans 13 to reserve the sword to the state, and/or the complete absence of any punishments save excommunication in the NT. I think the church needs to be far hotter on false teaching AND that its role is not to kill. Apr 12, 2023 at 1:18
  • Also, on Catholicism's own terms, wouldn't Pius IX be wrong if he contradicts an ecumenical council rather than vice versa? Apr 12, 2023 at 1:20
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    Freedom of speech and of the press and that "LIBERTY OF CONSCIENCE AND WORSHIP IS EACH MAN’S PERSONAL RIGHT" are insanity? Shall a man truly love God with a gun pointed at his head? Jesus taught no such thing. "Whosoever will, let him take the water of life freely!" I believe that you are representing Catholicism but you cannot really believe you are representing the Gospel of God by advocating for the burning of heretics. Apr 12, 2023 at 13:03
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    Any example from the Gospels, the Acts of the apostles, or the epistles advocating for or demonstrating the burning of an heretic would definitely buttress your case...have you any? Apr 12, 2023 at 21:53
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    " but you don't have any counter-arguments" Here's one: "Dearly beloved, avenge not yourselves, but rather give place unto wrath: for it is written, Vengeance is mine; I will repay, saith the Lord. Therefore if thine enemy hunger, feed him; if he thirst, give him drink: for in so doing thou shalt heap coals of fire on his head. Be not overcome of evil, but overcome evil with good." - Romans 12:19-21 Apr 13, 2023 at 13:14

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