CALLISTO I, patriarch of CONSTANTINOPLE. –
At first a monk on Mount Athos and a convinced follower of the doctrine of Gregory Palamas, he succeeded Isidore I on the ecumenical see in 1350, occupying it until 1354–55, when he was forced to resign because he refused to crown Matthew Cantacuzenus, associated with the empire by his father John. Since Matthew abandoned the throne in 1355, C. resumed his functions, which he held until his death (1363). During his patriarchate, the Palamite Council of 1351 was held at the Blachernae Palace, and it canonized the doctrine of Gregory Palamas. Anti-Palamite historians, such as Nicephorus Grégoras, portray C. as a narrow-minded and brutal man, whose zeal against his adversaries had to be moderated. He distinguished himself as a hagiographer and preacher.
The following works by him are known: 1) a Life of Gregory the Sinaite (d. in 1310), published by J. Pomjaloski, in St Petersburg, in 1894; 2) the Life of Theodore of Tirnovo, preserved only in Slavonic: cf. Byzantinische Zeitschrift, 15 (1906), p. 386; 3) a Panegyric of John the Faster, the restorer of the Constantinopolitan monastery of Petra, in the eleventh century, edited by H. Gelzer, Kalliston Enkomion auf Joannes Nestentes, in Zeitschrift für Wissenschaftliche Theologie; 29 (1886), pp. 64–89; 4) an unpublished Sermon Collection comprising 52 discourses and homilies, preserved in cod. 8 of the Athonite monastery of Chilandar, from the fifteenth century; 5) a Panegyric of the Cross, published by I. Gretser in his collection: De Cruce Christi, Ingolstadt 1600: in Opera omnia, II, Regensburg 1734, pp. 187–97; 6) a Homily on the Dormition of the Virgin, published in the journal Ἐκκλησία 1705 Φάρος, 8 (1911), pp. 114–49; the author does not express himself clearly concerning the Assumption properly so called; 7) a Sermon on the Beheading of St John the Baptist, contained in cod. theol. graec. 279 of the National Library of Vienna.