Jus novum (c. 1140-1563) Jus novissimum (c. 1563-1918) Jus codicis (1918-present) Other Sacraments Sacramentals Sacred places Sacred times Supra-diocesan/eparchal structures Particular churches Juridic persons Philosophy, theology, and fundamental theory of Catholic canon law Clerics Office Juridic and physical persons Associations of the faithful Pars dynamica (trial procedure) Canonization Election of the Roman Pontiff Academic degrees Journals and Professional Societies Faculties of canon law Canonists Institute of consecrated life Society of apostolic life Ad tuendam fidem (English: To Protect the Faith) is an apostolic letter of Pope John Paul II issued motu proprio on May 18, 1998.

[1] The apostolic letter modified the Oriental and Latin codes of canon law specifying the form of profession of faith to be made by ministers of the Church before assuming office.

The second level is that of doctrines likewise infallibly taught not as revealed by God but as truths inseparably connected with revelation.

The third category is that of teachings on matters more or less loosely connected with revelation that without being set forth with the solemnity of infallible doctrines are nevertheless authoritative.

The second category includes teachings on such matters as the illicitness of euthanasia, prostitution and fornication, and on what are called "dogmatic facts", such as the canonization of saints and the invalidity of Anglican ordinations.