ARSENIUS AUTORIANUS (13th century), patriarch of Constantinople, lived about the middle of the 13th century. He received his education in Nicaea at a monastery of which he later became the abbot, though not in orders. Subsequently he led a life of solitary asceticism in a Bithynian monastery. From this seclusion he was called by Theodore II. Lascaris in A.D. 1255 to the position of patriarch at Nicaea, and four years later, on the death of Theodore II. became joint guardian of his son John. His fellow-guardian Georgios Mouzalon was immediately mur dered by Michael Palaeologus, who assumed the position of tutor. Arsenius then took refuge in the monastery of Paschasius. In I261 Michael, having recovered Constantinople, induced Arsenius to undertake again the office of patriarch, but Arsenius excom municated the emperor for having ordered the young prince John to be blinded.
He was banished to Proconnesus, where some years afterwards (according to Fabricius in 1264; others say in 1, 7J) he died. He declined to remove the sentence of excommunication which he had passed upon Michael, and after his death, when the new patriarch Josephus gave absolution to the emperor, the quarrel was carried on between the "Arsenites" and the "Josephists." The "Arsenian schism" lasted till 1315, when reconciliation was effected by the patriarch Niphon (see Gibbon, Decline and Fall of the Roman Empire, ed. J. B. Bury, IS9S, vol. vi. 467 et seq.).
Arsenius is said to have prepared a summary of ecclesiastical laws under the title Synopsis Canonum. This was published (Greek original and Latin version) by G. Foal and H. Justel in Bibliotheca fur. Canon. l'et. (1661), 749 et seq. Some hold that the Synopsis was the work of another Arsenius, a monk of Athos (see L. Petit in Cacant's Diet, thctol. cathol., i. col. 1,994) ; the ascription depends on whether the patriarch Arsenius did or did not sojourn at Mt. Athos.
BIBLIOGRAPHY.—See Georgius Pachymeres ii. 15, iii. passim. iv. 1-16; Bibliography.—See Georgius Pachymeres ii. 15, iii. passim. iv. 1-16; Nicephorus Gregoras iii. I. iv. I.; for the will of Arsenius see Cotelerius, Monumenta ii. 168.