ARNOBIO il GIOVANE. – Christian writer, probably a monk, who lived in Rome around the middle of the 5th century; perhaps originally from Gaul. The scant and uncertain information we have about his life is matched by an equal uncertainty concerning his work as a writer, which recent criticism, especially through the efforts of the Benedictine G. Morin, has sought to reconstruct. In addition to the Commentarii in Psalmos (PL 53, 486 and 552), he is probably the author of some insignificant Expositiunculae in Evangelium (ed. by G. Morin in Anecdota Maredolana, III, 3, Maredsous 1903, pp. 129–51) and of the Conflictus Arnobii catholici cum Serapione Aegyptio (PL 73, 569–80), a superficial polemic against the Monophysites. Morin also attributes to him a Libellus ad Gregoriam (ed. by G. Morin, in Etudes, textes, découvertes, I, Maredsous 1913, pp. 383–439), a pamphlet previously attributed to Giovanni Crisostomo, in which the Roman lady Gregoria is shown the way to rediscover happiness in married life, as well as the treatise in three books Praedestinatus (PL 73, 587–672). The importance of these works lies in the position taken in them, especially in the Commentarii and the Praedestinatus, regarding the debated question of grace and predestination, in more or less open opposition to the extreme ideas professed by s. Agostino in his polemic against the Pelagians, particularly Giuliano d'Eclano.
An examination of the Praedestinatus shows that A. is rather a Semipelagian than a Pelagian in the manner of Giuliano d'Eclano, and that he presents, as the creed of a supposed Predestinarian heresy, an original composition intended to discredit Augustinian doctrines. The spiritual attitude of the author of the Commentaries on the Psalms is no different, although closer to orthodoxy, since the harm inflicted on humanity by original sin is acknowledged and deplored; the high regard accorded in both works to the ascetic ideal and to the continent life constitutes an evident link between them. Everything therefore leads to the conclusion that the author is the same. The problem remains of determining how the same author could, in the Conflictus, have subscribed to Augustinian theses. Morin thinks that the author freed himself from the ideas of Pelagius “as the increasingly clear action of Roman authority... made him see the expediency of doing so.”