Orsisius (Greek: ‘Arsisios, 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 favor of Theodore. It was not till Theodore’s death (c. 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 savored 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., CIII, 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.
ADRIAN FORTESCUE