This Index of Louvain is distinctive in being the first of the long series of catalogues of books and of authors condemned as heretical which were issued with the sanction of the Church. It antedates by thirteen years the first of the Indexes produced in Rome, under the immediate supervision of the pope, and may possibly be considered as an example of the special zeal against heresy on the part of the ecclesiastical authorities of the Spanish realm and of the effectiveness of the Spanish Inquisition. As the later records give evidence, it was only in the territory in which the authority of the Inquisition remained unquestioned and by means of its machinery that it proved practicable to carry out with any thoroughness the policy of the Church in regard to the ecclesiastical control of literary productions. The faith of the believing subjects of the Emperor Charles was threatened most seriously by heretical writings coming from Holland and from Germany, and it was therefore quite fitting that the first official protest of the Church should be made from a place like Louvain, the university of which stood like a picket-post of orthodoxy confronting the perilous heresies advancing from the North and from the East. The name of the Inquisition is not directly connected with this first Index of Louvain, but it appears on that printed at the same place four years later, which is in substance a reissue of the catalogue of 1546, and it is probably the case that the command of the Emperor for the preparation of the earlier publication may be credited to the Senate of the Inquisition. The _Mandement_ makes reference to _Ordonnances_ for the restraint of the press, issued in 1540 and 1544. It complains of the continued publication of heretical books, and particularly of corrupt editions of the Scriptures; and it accordingly subjects booksellers to new restrictions, under penalty of death if they sell any books containing error, without the previous inspection and mark of the appointed inspectors. No books could be printed except by a duly certified printer who was a member of the guild. The Index itself comprises, 1, a list of Bibles and New Testaments in Latin, low German, and French editions; 2, a list of works in Latin, chiefly the writings of the German Reformers (these titles are repeated in Flemish); 3, a list of heretical works in German and French; and, 4, a list of books which had been condemned in the rescript of 1540.