Council of Trent (1545–1563).
Sacros. Concilium Tridentinum: Editio reformata . . . cum indice librorum prohibitorum ex praescripto Concilii.
Cologne: Johann Busäus, 1664.
The Tridentine Index of 1564 presented ten rules established by the Council of Trent to guide the censorship of texts. In the Index librorum prohibitorum issued with this 1664 edition of the Council’s decrees, the ten rules are reprinted in full. These are summarized here in English:
1. All books condemned by popes or councils before 1515 will remain prohibited.
2. All books by “heresiarchs” (heretical leaders) and theological books by heretics are prohibited.
3. Heretics’ Bible translations are banned; heretics’ translations of other texts require approval.
4. Vernacular translations of the Bible by Catholic scholars require approval.
5. Compilations of earlier works edited by heretics require correction and approval.
6. Theological writings in vernacular languages require correction and approval.
7. Obscene or immoral works are prohibited; Classical works may be read by adults.
8. Books that are generally sound, but which contain isolated heresies must be corrected.
9. All books treating magic, superstition, astrology, or occult practices are prohibited.
10. The bishop and the inquisitor require all books to be licensed prior to publication.
These rules, expanded and modified over the centuries, remained the core determinants for Catholic censorship until use of the Index librorum prohibitorum was discontinued in 1966.