Zosimus pope in A.D. 417418, successor to Innocent I, was by birth a Greek and is noteworthy as a participant in the doctrinal controversies of his time, in which he first endorsed and then rejected doctrines regarded as heretical, and also for his assertion of authority and his energetic labors in behalf of the supremacy of the Roman see. He countermanded the condemnation of Pelagius and Coelstids, denounced by Innocent and the African synods; and in a letter to bishop Aurelius of Carthage and others he censured the treatment they had received declared them orthodox, and warned the bishops against, sophistries in speculation. He also cited before his bar Paulinus, the accuser of Pelagius. The African bishops however, held another synod 418, which defined their course and censured Zosimuis for a reopening a settled case, besides forbidding the departure of Paulinus for Rome. Zosimus, endeavored to fortify his position by a reference to the ecclesiastical authority derived by his see from Peter; but when tithe, Africans obtained a sacrum rescriptum against the Pelagians from the emperor Hoisorius, he gave way, and, for his art pronounced the condemnation of Pelagius and Coelestius in an Epistola Tractatoria. This time he was opposed by eighteen Italian bishops whom he at once declared deposed. The deposition of the presbyter Apiarius of Sicca, in Numidiaand his appeal to Zosimus against his bishop, Urbaitus, led to fresh disputes with the Africans. Zosimus refused to recognize the deposition, and sent three delegates to a synod convened at Garthage to demand the restoration of Apiarius.
Zosimus also interfered in the affairs of the Gallican bishops by appointing bishop Patroclus of Arelate his vicar in Gaul, and conferring upon him the rights of metropolitan over the province of Vienne. His course excited much opposition; but death put an end to his plans for aggrandizement in 418. See Schröckh, Kirchengesch. (Leips. 1782), 8:148 sq.; Gieseler, Kirchengesch. (4th ed. Bonn. 1845), 1, 2, 111 sq. — Herzog, Real Encyklop. s.v.