Politician, writer, and monk (c. ad 490–c.585). His Bruttian family had a tradition of provincial leadership and official service. He assisted his father, praetorian prefect of Italy, 503–7, under the Ostrogothic king Theoderic. Writing Theoderic's diplomatic letters in 506, he was quaestor sacri palatii (rhetorical draftsman and legal adviser), 507–12. Consul in 514, in 523 he replaced his disgraced kinsman Boethius as magister officiorum (‘master of the offices’, a very senior official with extensive responsibilities for the working of the central bureaucracy, but also with draftsman's duties); he served into 527, aiding the new reign of Athalaric and Amalasuintha. Prefect of Italy from 533, he was again both administrator and royal draftsman. With Pope Agapitus (535–6), he planned an abortive school of Christian higher education at Rome. Remaining prefect under kings Theodahad and Witigis, and made patrician, he retired in 537/8 during the Gothic wars. Moving to Constantinople, he assisted Pope Vigilius in the Three Chapters controversy (550). Soon after, he withdrew permanently to his monastery of Vivarium on his ancestral estate at Scylacium. There he organized translations and manuscript copying, partly to support the Three Chapters against official condemnation, partly to promote Christian education. Vivarian texts soon circulated widely, but the monastery quickly shared in the decay of Italian civilization.
Among his works: (1) a short chronicle of the world and Rome, ordered by Theoderic's son-in-law Eutharic, when consul in 519. (2) A lost, tendentious Gothic history, extensively used in Jordanes’ Getica (c.551). Notable for its untrustworthy pedigree of Theoderic's Amal family and use of Gothic legend, it is the first known ethnic history from the barbarian kingdoms, integrating Goths into the classical past. (3) Panegyrics (fragmentary) on Gothic royalties, last of the Latin prose genre. (4) Variae: twelve books of state papers, edited c.537, an invaluable source for Ostrogothic Italy, and the structures, culture, and ideology of late-Roman government. The collection was both an apology for the Ostrogoths and their Roman collaborators, and a moral, rhetorical, and practical guide for future rulers and ministers; Cassiodorus' blending of ekphrasis (extended literary description of a real or imaginary object) and learned digression into official discourse is remarkable. (5) The appended De anima grounded the Variae in religious reflections on human nature and society. (6) Expositio Psalmorum: this exegetical and literary commentary developed the Psalms as a Christian rhetorical handbook and encyclopaedia of liberal arts, superseding pagan classics. (7) Institutiones: an intellectual Rule for Vivarium (but also meant for a wider public), this short encyclopaedia and bibliography of Christian and secular studies renewed the project of Christian higher education, and depicted reading (including the liberal arts) and copying as central to monastic life. (8) De orthographia: a guide for Vivarian copyists. Among influential Vivarian translations were Josephus' Antiquitates, and the ecclesiastical Historia tripartita, combining Socrates Scholasticus, Sozomen, and Theodoret. Cassiodorus did not save classical culture, as is sometimes claimed; but, especially from Carolingian times, Variae, Expositio, and Institutiones were widely read, and helped to maintain and integrate the Christian and Roman inheritances in western Europe.