CANON THEOLOGIAN. - In every cathedral church there must exist the office of canon theologian, which may also be established in collegiate churches, especially notable ones (can. 398, § 1). If there is no incumbent capable of fulfilling this role, the office must at least be established.
I. The office of canon theologian originated during the pontificate of Innocent III in a decree of the Fourth Lateran Council (1215), worded as follows: “In every metropolitan church a theologian must be designated, entrusted with the mission of interpreting Sacred Scripture and teaching the faithful what pertains to the pastoral ministry” (L. Thomassin, *Antiqua et nova disciplina Ecclesiae circa beneficia*, Lucca 1728, I, cap. 1; II, cap. 10, n. 1). This decree, extended to cathedral churches by the Council of Basel, was solemnly promulgated by the Council of Trent (sess. V, c. 1). The person chosen for this office shall be the one who, given local circumstances, is best suited to perform these duties; all else being equal, a doctor—and preferably a doctor in theology—shall be designated (can. 399, §§ 1–2). Following the motu proprio *Bibliorum scientiam* of Pius XI, dated 27 April 1924, the canon theologian, charged with explaining Sacred Scripture to the faithful, must have obtained academic degrees from the Biblical Commission or at least received the title of bachelor from the Biblical Institute of Rome (AAS, 16 [1924], pp. 180–82).
2. The canon theologian, on the days and at the hours fixed by the bishop after consulting the Chapter, shall publicly expound Sacred Scripture in the cathedral or collegiate church. If the bishop deems it opportune, he may entrust the theologian with teaching other branches of Catholic doctrine, such as dogma and moral theology. Moreover, for a grave reason, the canon theologian may be called upon to teach sciences in the seminary rather than deliver these lectures in church; such a grave reason exists when the bishop cannot find another competent professor for the purpose. In this case, the canon theologian who obeys his bishop is considered to be exercising the functions of his office and does not forfeit any of his canonical rights (can. 420, § 1, n. 2).
3. The canon theologian, like all canons, is appointed by the bishop, unless in certain capitular churches the choice is subject to a competitive examination, a system that, if it exists, is to be preserved (can. 399, § 2).
4. The canon theologian shall personally fulfill his duties; if, however, he is prevented from doing so for a period exceeding six months, he is bound to arrange for a substitute priest, designated by the bishop, to take his place at his own expense (can. 400, § 2).
The canonical penalties applicable to the canon theologian are the same as those for the canon penitentiary (v. can. 2384).