We are, however, much better instructed in regard to the Church of the fourth and early fifth centuries, because the century following the Council of Nicæa was, in the history of church literature, what the Elizabethan era was in that of England. It was the era of the great "fathers" of Christian theology, to whom all theologians since have looked back as to the foremost interpreters of their religion. Among the chief of these were Athanasius (d. 373), to whom is attributed the formulation of the creed of the Orthodox Church as opposed to the Arians, against whom he waged unremitting war; Basil (d. 379), the promoter of the monastic life; Ambrose, Bishop of Milan (d. 397); Jerome (d. 420), who prepared a new Latin version of the Scriptures, which became the standard (Vulgate) edition; and, above all, Augustine (354-430), whose voluminous writings have exercised an unrivaled influence upon the minds of Christian thinkers since his day. Since the church fathers were chiefly interested in matters of doctrine, they say little of the organization of the Church, and it is not clear from their writings that the Bishop of Rome was accorded as yet the supreme and dominating position which the popes later enjoyed. Nevertheless, Augustine calls a contemporaneous Bishop of Rome the "head of the Western Church," and almost immediately after his death one ascended the episcopal chair at Rome whose ambition, energy, and personal bravery were a promise of those qualities which were to render his successors the kings of kings. [Sidenote: Leo the Great, 440-461.] [Sidenote: Decree of Valentinian III.] With the accession of Leo the Great (440-461) the history of the papacy may, in one sense, be said to have begun. At his instance, Valentinian III, the emperor of the West, issued a decree in 445 declaring the power of the Bishop of Rome supreme, by reason of Peter's merits and apostolic headship, and by reason of the majesty of the city of Rome. He commanded that the bishops throughout the West should receive as law all that the Bishop of Rome sanctioned, and that any bishop refusing to answer a summons to Rome should be forced to obey by the imperial governor. But a council at Chalcedon, six years later, raised new Rome on the Bosphorus (Constantinople) to an ecclesiastical equality with old Rome on the Tiber. The bishops of both cities were to have a co-superiority over all the other prelates. This decree was, however, never accepted in the Western or Latin Church, which was gradually separating from the Eastern or Greek Church whose natural head was Constantinople.[28] Although the powers to which Leo laid claim were not as yet even clearly stated and there were times of adversity to come when for years they appeared an empty boast, still his emphatic assertion of the supremacy of the Roman bishop was a great step toward bringing the Western Church under a single head. [Sidenote: Duties that devolved upon the early popes.]