Orsisius (Ἀρσίσιος, Oresiesis-Heru-sa Ast), an Egyptian monk of the fourth century, was a disciple of Pachomius on the island Tabenna in the Nile. When Pachomius died (348), Orsisius was chosen as his successor; but he resigned in favour of Theodore. It was not till Theodore’s death (¢. 380) that Orsisius, advised by St. Athanasius, accepted the office of hegumen. Theodore and Orsisius are said to have helped Pachomius in the composition of his rule; Gennadius (De. vir. ill, IX) mentions another work: “Oresiesis the monk, a colleague of Pachomius and Theodore and a man perfectly learned in the Scriptures, composed a Divinely savoured book containing instruction for all monastic discipline, in which nearly the whole Old and New Testaments are explained in short dissertations in as far as they affect, monks; and shortly before his death he gave this book to his brethren as his testament.’ “This is supposed to be the work: “ Doctrina de institutione monachorum” translated by St. Jerome into Latin (P. L., CII, 453 sq., and P. G., XL., 870-894). Migne prints after it (P. G., XL, 895 sq.) another work attributed to the same author: “De sex cogitationibus sanctorum”, which, however, is probably by a later Oresius.
Cave, Scriptorum eccl. historia literaria, I (Basle, 1741), 209; has re wr, [Llistoire générale des auteurs sacrés, IV (Paris, 1860), OO Sc.
Adrian Fortescue.