Joannes de Deo
JOANNES DE DEO
Canonist, b. Silves, Portugal, end of 12th century; d. Lisbon, March 15, 1267. He studied under Zoen, Archpriest of Bologna, later bishop of Avignon (after 1240), to whom he dedicated several works. As professor in the University of Bologna he published many treatises with valuable information about decretists and decretalists.
His Principium decretalium is very important for the history of the Compilationes. Among his early works are the Casus decretalium, Breviarium decretorum, Distinctiones super toto iure canonico, Arbor versificata, and Chronica, all of which were mentioned in Liber iudicum (1238). Later appeared the Apparatus decretorum (before 1241), Epistulae canonicae de decimis (May 30, 1240), Notabilia cum summis super titulis decretalium (dedicated to Cardinal Gil Torres, Sept. 1241), Casus Legum canonizatarum (Sept. 1, 1241), and the Summa super quattuor causis decretorum (1243), which is a continuation of the Summa Huguccionis, and contains a list of all his earlier works. The Liber dispensationum, published Aug. 28, 1243 and dedicated to Dominican and Franciscan friars, with a list of his earlier works, was submitted to Innocent IV for correction. It is a complete recension, some parts of which had been published before the election of the pope. In the dedication (after 1248) of the Liber Cavillationum (dated Sept. 2, 1246) to Cardinal William, and of the Liber quaestionum to Cardinal Ottaviano Ubaldino (Sept. 6, 1248), he lists the Liber pastoralis (August 1244) dedicated to Cardinal William of Sant' Eustachio and the Liber poenitentiarius dedicated to the Bishop of Lisbon (Oct. 28, 1247). The above lists do not mention other authentic works: Concordantiae decretorum cum titulis decretalium, De electione, Principium decretalium, De abusibus contra canones (an appendix to the Liber poenitentiarius ), Liber opinionum, which was submitted for correction to Innocent IV in October 1251, and the Summula super decimis ecclesiasticis, a letter urging the Dominicans to preach about the duty of paying tithes, with the addition of a prologue and further considerations on the same subject addressed to Alexander IV and the cardinals. Even if some of these works are not very original, they are valuable for their rich indication of sources.
Joannes de Deo was appointed judge several times, even by Popes Innocent IV and Alexander IV. Upon his return to Portugal, he was archdeacon of Santarém in Lisbon in March 1260, and was appointed judge and arbiter in lawsuits. One of them concerned the Monastery of S. Cruz in Coimbra, and in it Pedro Julião, the famous philosopher and later Pope John XXI, was also involved.
Bibliography: a. d. de sousa costa, Um mestre português em Bolonha no século XIII (Braga 1957). a. van hove, Commentarium Lovaniense in Codicem iuris canonici 1, v.1–5 (Mechlin 1928—) 1:477, 480, 484–486.
[a. d. de sousa costa]