which had
previously emitted thought of pregnant import for the modern world, and
to prevent the reflux of ideas, elaborated by the northern races in
fresh forms, upon the intelligence which had evolved them. To do so now
was comparatively easy. It only needed to put the engine of the Index
Librorum Prohibitorum into working order in concert with the
Inquisition.

Throughout the Middle Ages it had been customary to burn heretical
writings. The bishops, the universities, and the Dominican Inquisitors
exercised this privilege; and by their means, in the age of manuscripts,
the life of a book was soon extinguished. Whole libraries were sometimes
sacrificed at one fell swoop, as in the case of the 6000 volumes
destroyed at Salamanca in 1490 by Torquemada, on a charge of
sorcery.[111] After the invention of printing it became more difficult
to carry on this warfare against literature, while the rapid diffusion
of Protestant opinions through the press rendered the need for their
extermination urgent. Sixtus IV. laid a basis for the Index by
prohibiting the publication of any books which had not previously been
licensed by ecclesiastical authority. Alexander VI. by a brief of 15O1
confirmed this measure, and placed books under the censorship of the
episcopacy and the Inquisition. Finally, the Lateran Council, in its
tenth session, held under the auspices of Leo X., gave solemn ecumenical
sanction to these regulations.

The censorship having been thus established, the next step was to form a
list of books prohibited by the Inquisitors appointed for that purpose.
The Sorbonne in Paris drew one up for their own use, and even presented
a petition to Francis I. that publication through the press should be
forbidden altogether.[112] A royal edict to this effect was actually
promulgated in 1535. Charles V. commissioned the University of Louvain
in 1539 to furnish a similar catalogue, proclaiming at the same time the
penalty of death for all who read or owned the works of Luther in his
realms.[113] The University printed their catalogue with Papal approval
in 1549.

[Footnote 111: Llorente, vol. i. p. 281.]

[Footnote 112: Christie's _Etienne Dolet_, pp. 220-24.]

[Footnote 113: Llorente, vol. i. p. 463.]

These lists of the Sorbonne and Louvain formed the nucleus of the
Apostolic Index, which, after the close of the Council of Trent, became
binding upon Catholics. When the Inquisition had been established in
Rome, Caraffa, wh