The Index librorum prohibitorum - the dreaded Index - is the official list of books once prohibited by the Catholic Church.
The Index dates back to the momentous years of the Counter-Reformation, when the church (and many state) authorities felt themselves to be in the midst of the ultimate battle for the souls of humanity - or their lucrative power base, depending on which side of the Reformation you're on.
One of their bright ideas, along with torture and burning people at the stake, was to compile a single list of books that no God-fearing man (and I use the term advisedly) should possess or read.
The idea was first formally introduced in 1557 with the publication of the Index auctorum et librorum prohibitorum under the direction of Pope Paul IV. The Pauline Index, as it became known, was the first in a long succession of papal indices, forty-two in all.
The 32nd edition, for example, published in 1948, contained 4,000 titles, including many that were banned on the basis of politics or morality, rather than heresy.
Authors who made it onto the ultimate A-list include Hugo, Rabelais, Balzac, Zola, Flaubert and Voltaire - basically the golden ages of French literature. Pierre Larousse, compiler of the Grand Dictionnaire Universel, found it banned after all those years of work. Words, it seems, are dangerous even if only in dictionaries.
Perhaps more significant in terms of the effects on other writers and thinkers were the bans on Copernicus and Galileo (for trying to understand the universe), Spinoza (expelled by the Jewish community as well), Erasmus (perhaps the greatest mind of all) and Bruno (who burned along with his books). Those of you who suffered through Milton at school may be shocked to learn he made the list (he was a die-hard Puritan), as did swashbuckler Dumas, pirate enthusiast Defoe, and Swift of Gulliver fame. They were in good company, along with Descartes, Machiavelli, Locke, Hume, Paine, Rousseau and even Madame De Stael: perhaps the only thing these names have in common is that what they wrote was banned.
More recently, of course, the Index has included books by Gide, Sartre and Joyce but, strangely enough, not Adolf Hitler's Mein Kampf. Even more amazingly, recent research indicates that the inquisitors in the Sacred Congregation of the Index never had a problem with Darwin.
It was in force until a mere forty years ago this week. Another Paul, Pope Paul VI, abolished the Index on June 14 1966.
As we know, there are plenty of people who wish it were still in place - with JK Rowling's name high on the list.
Whenever they burn books they will also, in the end, burn human beings.
~ Heinrich Heine (who was also on the Index)