“It remains to consider what the character of the Index is and what the object was in planning and compiling it. For a catalogue of prohibited books does not go as far as to note each and every bad book. Obviously this would not be done, nor, if the principle of the Decretals be grasped, does it appear necessary. There must, therefore, be some special reason why the Roman Congregations black-list by special decree a book already included in those classes noted by the Decretals. This reason is furnished in most cases by denunciations, from a bishop or other of the persons specified in _Const. Off. ac Mun._, vv. 27, 28, 29, recommending a given book to the Holy See for examination as destructive or dangerous. Following this clue, and not of set purpose choosing the worst among all the books in existence, the Holy See is very often led to examine other books not included by the Decretals. Therefore, it would be vain to seek in the Index either all noxious and wicked books or those distinguished as it were for wickedness in any department, or to demand that the books in the Index be dealt with in a fixed order based on either the argument or the matter. The only basis of the Index is then this, that it notes those works which for any reason have been prohibited by special decree during the last three centuries, whether by popes in Apostolic letters or by Roman Congregations, and especially the Congregation of the Index, so that neither oblivion nor ignorance may obscure the dangerous character of their contents.