All organized religions experience a program of codification in which certain practices and literature are approved by a controlling body while other practices, books, myth and lore are disapproved and sometimes officially banned. Initially, much of this had political motivation—to bring the "faithful" under a single roof and to eliminate deviancy and competition to Roman rule in the case of early Christianity.
Until the middle of the 20th century, certain books were listed as "sinful" for Catholics to read, and such banning was not limited to books with sexual themes although that was the common interpretation.
Only in recent years has there been widespread opportunity to explore alternatives in Christianity, and—to a lesser extent—in Islam and Judaism. In some cases, it has been archaeological finds that brought old ideas into new perspectives. For Christians, the primary findings have related to Gnosticism and Neoplatonism.