The Church started censoring books in the 1500s shortly after the invention of the printing press when common people began to have access to books, because prior to the printing press books were time consumingly painstakingly hand copied, i.e. the information they received about religion could come from somewhere other than the pulpit at mass, indeed also from any of the other newly formed heretical Christian sects like Martin Luther’s. For the benefit of the laity, that is to prevent souls from otherwise being lost and going to hell, the church had official approbations (Nihil Obstat and Imprimatur) for books to verify they were free of doctrinal or moral error. This did not imply that those who had granted the nihil obstat and imprimatur agreed with the contents, opinions or statements expressed.
Books THAT DID CONTAIN doctrinal or moral error were placed in the “Index, or Index of Prohibited Books, is simply the list of books which Catholics are forbidden by the highest ecclesiastical authority to read or retain without authorization. An edition was published in 1925.”
To implement censorship the church created the Congregation of the Index. “This congregation so called from the Index of catalog of forbidden books, was created by Pius V, in 1571. Benedict XV suppressed it on 25 March 1917, its duties being left entirely to the Holy Office. The Congregation of the Index consisted of a number of cardinals, one of whom was its prefect. The Master of the Sacred Palace (a Dominican) was ex officio its assistant, and another Dominican its secretary. There was also a college of consultors whose office was to deliver written opinions on the books submitted to their judgement by the congregation. The congregation censured and condemned books which it considered dangerous to faith or morals. It could grant permission for the reading of a condemned book, or for the publication of corrected editions. The congregation was also charged with the work of seeking out pernicious publications, and, after mature examination, of condemning and proscribing them.”
The “Censors of Books, clerics, in practice always priests, appointed according to canon law by the bishop of a diocese to examine, before publication, those writings or other things that are to be submitted to ecclesiastical supervision. The censors are to be chosen either from the secular or regular clergy. Conditions of age, learning, and prudence are to be considered in naming them. As a guarantee of fitness, the censors, before entering upon their office, make a profession of faith before the bishop or his vicar-general. In examining what is submitted to them, they must lay aside favoritism, and consider the teachings of the Church and the laws of sound morals in order to determine whether the things in question may be given to the public with safety. In each case the censor must give his opinion in writing. If his opinion is favorable, the permission to publish is granted. The fact of the favorable view of the censor must be shown on the publication. This is usually done by placing there the Latin words, Nihil obstat, meaning “Nothing hinders the publication,” and the name of the censor, then follows the word, Imprimatur, the name of the local bishop or of his vicar, and the place and date of permission. Chiefly works on religious subjects or those which have a bearing on religion are presented for censorship. See Imprimatur.[below]”
“Imprimatur, im-pri-ma’ tur (Lat.. it may be printed), word placed at the beginning or end of certain things published. It shows that those publishing them have complied with the law of the Church, which requires that writings on given topics, or even some images, be submitted to an ecclesiastical censor for examination before they are put forth. See Censors of Books[above].” The above 4 quotes are entries from a 1929 copy of the New Catholic Dictionary published by the Universal Knowledge Foundation, New York.
Traditional Thomistic Catholic 