The Index of Expurgations
The Index librorum expurgatorum (“Index of Expurgated Books”) was designed to allow books that were only partially objectionable to be circulated as soon as corrections by an ecclesiastical censor had been entered. Such indexes listed the specific passages of books that required censorship in the expectation that all copies would be brought forward to the censor for physical correction. This correction usually took one of three forms: deletion of the text by applying ink over the printed passage, deletion of the text by gluing blank paper over the printed passage, or removal of the text by cutting the leaves containing the passage out of the book. In rare cases, the correct words were substituted in place of incorrect ones. Typically, the censor would sign and date the book to certify that it had been expurgated correctly. Not all expurgated books were considered heretical. Many books of mainstream Catholic orthodoxy were expurgated simply because they contained errors.