The Index of Prohibited Books has a bad reputation today. But even 21st-century secularists suppress ideas they consider dangerous

It’s like the movement against smoking. The authorities decide that they must keep people from smoking for their own good. Many would ban it if they could, but they can’t, so they require scary warnings on packages, don’t let anyone smoke in public places, prevent sales to minors, restrict advertising and raise the price with really high taxes. The point is to save smokers from themselves.

That’s one of our parallels to the Index of Prohibited Books, abolished 50 years ago this month by the newly renamed Sacred Congregation for the Doctrine of the Faith. The idea – judging from the way I used to think and the way others speak about these things – sounds funny to us, raised believing in the open marketplace of ideas and with the feeling that ideas may be good or bad but they’re not really agents in the world. But the idea of an index only sounds funny to us because we don’t think of ideas as dangerous. We recognise physical infections but not intellectual ones.

In that, the advantage goes to the men who invented the Index and kept it going. They took ideas seriously. They thought some ideas would poison you just like nicotine-filled smoke and that some people who might innocently indulge should be protected from poisoning themselves.

It still sounds funny to us, banning books, because we don’t think of them as dangerous – except that we do. Some years ago the American libertarian Charles Murray and a Harvard psychologist named Richard Herrnstein published a long, studies-filled book called The Bell Curve, which argued that the races differed in intelligence, and it was duly attacked by those on the Right as well as the Left.

Most argued that the authors were wrong, but also that the idea would let every racist, social Darwinist and neo-fascist in America claim that their bigotry was “scientific” and “realistic,” and that they were only “facing facts”. The book is still regularly invoked as a bad thing.

In mainstream American discussion, it’s on an informal index, but one no less effective for being so. An academic who endorsed the book would ruin his chances of getting a job at almost any university in America.

The Index of Prohibited Books was created at the Council of Trent, after the invention of mass printing and the spread of literacy made the matter of a book’s influence a live one. It addressed only books affecting faith and morals, although as the Church was working out its relation to the new science, works by Copernicus, Kepler and Galileo were added (and later removed). As developed by Pope Benedict XIV in the mid-18th century, it required a “blind” peer review and dialogue with the author whose book was being challenged.

The books included varied over time (the last published list appeared in 1948). Most of them only scholars would now recognise, but the list also included books by philosophers such as Rousseau and Hume, and writers including Milton, Montaigne, Voltaire and Zola. The choices inevitably varied in quality and a few books came off the list when the Congregation decided they weren’t so dangerous after all.

Two more things should be said about the Index, beside the fact that it expresses a normal human action which modern secular people take. First, it was the mechanism that was abolished, not the teaching that the Church should judge particular books and that Catholics should take care in what they read. In announcing the abolition, Cardinal Ottaviani, prefect of the Congregation, noted that “The Index preserves its moral force, in so far as it teaches the conscience of the Christian faithful, so that, since natural law itself demands [it], they may guard against those writings, which can lead faith and morals into danger.” (The translation is by Professor Richard Smith of the Franciscan University of Steubenville.)

Ottaviani continued: “The Church trusts the developed conscience of the faithful, especially of Catholic authors and publishers, and also of those who assist the instruction of young people. Moreover, it places the firmest faith in the watchful care both of individual ordinaries and of episcopal conferences, whose is the right and duty not only of examining, but also of anticipating, and also, if the case should warrant it, of censuring and rejecting.”

Second, there’s one important distinction to be made. The Church wasn’t protecting her people from dangerous ideas but from dangerous errors. Truths can be dangerous. Much unkindness and cruelty has come from people who misapplied “There is no salvation outside the Church” and “There is no other name under heaven by which we must be saved.” Truths are like axes and hammers, tools that can be turned into weapons. The Church trusts people with the truth, though sometimes it comes with “This does not mean that …” warnings. With errors, it sets off the alarm.

David Mills, former executive editor of First Things, is editorial director of Ethika Politika (

This article first appeared in the June 17 2016 issue of The Catholic Herald. To read the magazine in full, from anywhere in the world, go here.