CensorshipBook burning was not the only way the Christians had of suppressing rational thought. Censorship was another method.
The Protestant reformation weakened the powers of the Roman Catholic Church. In an effort to suppress dissent, Pope Paul IV (1476-1559) published the Index Librorum Prohibitorum (List of Forbidden Books) in 1559. The Index, as it is normally called, was an official list of writers and books which Catholics are forbidden to own or read. The official justification for the Index was the suppression of heresy. In 1571, Pope Pius V (1504-1572) established the "Congregation of the Index" which main responsibility was the periodic updating of the list. The Index was kept in force, and updated, for more than four centuries. The last Index was published in 1966. The Index itself was officially abolished only in 1978. 
The list of books that made it into the Index reads like a modern library collection of the greatest books of all time. Thus we find the two most important books on astronomy included in the earliest lists of the Index: Copernicus' (1473-1543) On the Revolution of Heavenly Bodies (1543) and Galileo's (1564-1642) Dialogues on the Two Chief World Systems (1632).  There is no doubt that had the Roman Church the power it possessed a few centuries earlier, these books would have been burned to oblivion.
Books on philosophy were also placed on the Index. Baruch Spinoza's (1632-1677) Tractatus Theologico-Politicus (1670), certainly one of the classics of western philosophy, was promptly placed on the Index for attempting to deal with the origins of the Bible rationally. 
Great books of literature were also not spared from inclusion in the Index. Desiderius Erasmus' (1466-1536) satirical, The Praise of Folly (1509) was placed in the Index for criticizing, correctly, the corruptions of the church. 
The practice of putting books on the Index for the most trivial of reasons is continued into the twentieth century. One example is the book Ideal Marriage (1926) by T.H. van de Helde. It was placed on the Index purely because it advocated other methods of having sex apart from the missionary position. 
The Index also listed the names of writers whose books are not to be read by any Catholic. In the earliest Index it was not surprising that Protestant reformers such as Martin Luther (1483-1546) were placed on the list.  What is surprising is the list of banned authors in the last Index in 1966. Here we find the names of some of the greatest minds in history. Included in that list was: philosophers such as Francis Bacon (1561-1626) Thomas Hobbes (1588-1679), John Locke (1632-1704), and John Stuart Mill (1806-1873); authors such as Samuel Richardson (1689-1761), Alexander Dumas (1802-1870) and Victor Hugo (1802-1885); and even the great historian Edward Gibbon (1737-1794). 
The Index brought more harm to Catholics than to anybody else. As Barrie Strauss commented, the net result of the Index Librorum Prohibitorum was to "cut off the Catholic clergy and laity from the mainstream of intellectual life." 
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