The history of the Index may be divided into two main periods. The first begins, as far as the papal censorship is concerned, in 1559, with the publication of the _Index Auctorum et Librorum_, prepared under the instructions of Paul IV, and closes with the end of the 16th century, with the issue of the final appendices to the Index of the Council of Trent. During this period, the chief and almost the only subject-matters considered are the great questions raised by the Reformation. In the second period, which closes with the Index of Benedict XIV, issued in 1758, the controversies turn, as indicated by the character of the works placed on the lists, on issues of doctrine, opinion, and conduct arising within the Church itself. The writers whose works are condemned during this period are for the most part ecclesiastics of the Church. The work done during the 19th century by the Congregation of the Index may be said to belong to a third or modern period, in which, as will be noted later, the censorship over literature and the literary instruction for the faithful has for the most part taken the form of statements of general principles in place of detailed lists of pernicious books. The attempt to characterise the mass of the world’s literature has been abandoned and the comparatively few titles named are (with a few curious exceptions) those of doctrinal works emanating from within the Church itself and the errors in which are, therefore, likely to mislead believers. It is to be borne in mind further in connection with the general division of periods suggested by Reusch, that while the greater portion of the work of the Index was carried on under the direct supervision of the popes, a long series of Indexes were issued by authorities acting independently of the Papacy, such as the Inquisition of Spain, the theological faculty of the University of Paris, the theological faculty of the University of Louvain, and other bodies.