Pelagius, along with his friend Caelestius whom he had converted to his views, went from Rome to Africa (A.D. 409). Leaving Caelestius there, he proceeded himself to Palestine. Caelestius stated his views before a council of African bishops at Carthage and was excommunicated (A.D. 412). Three years later a synod was held at Jerusalem, at which Pelagius was present, the question was discussed, and it was decided that it should be referred to Pope Innocent I (A.D. 415), but some months later another synod at Diospolis acquitted Pelagius of heterodoxy. In the meantime Augustine was writing on the subject,39 and the African bishops condemned the Pelagian doctrine and asked Innocent to express his approval.40 A decision on the matter devolved upon Innocent’s successor Zosimus, who was elected on March 17, A.D. 417, and the ear of this Pope was gained by Caelestius, who had come to Rome. Zosimus censured the African bishops for condemning Caelestius, and intimated that he would decide, if the accusers came and appeared before him. Then he received a letter from Pelagius, which convinced him that Pelagius was a perfectly orthodox Catholic.41 But the African bishops were not convinced, and in defiance of the Pope’s opinion, they condemned Pelagius and his teaching in a synod at Carthage (May 1, A.D. 418). Zosimus at last became aware that the doctrines of Pelagius were really heretical; he was obliged to execute a retreat,42 and he confirmed the findings of the African synod. Honorius issued a decree banishing Pelagius and Caelestius from Rome and inflicting the penalty of confiscation on their followers.43 Although the views of the British heretic were crushed by the arguments and authority of Augustine, they led to the formation of an influential school of opinion in Gaul44 which, though condemning Pelagianism, did not accept the extreme predestinarian doctrines of the great African divine.
In the list of Roman pontiffs the name of Zosimus is not one which the Catholic Church holds in high esteem. His brief pontificate fell at a critical period, when the Roman see was laying the foundations of the supremacy which it was destined to gain by astute policy, and propitious circumstances, over the churches of western Europe. Zosimus, through his rashness and indiscretion, did as much as could be done in two years to thwart the purposes which he was himself anxious to promote. In the matter of Pelagius he committed himself to a judgment which shows that he was either unpardonably ignorant of the doctrine which had been challenged, or that he considered orthodox in A.D. 417 what he condemned as heterodox in A.D. 418; and he exposed himself to a smart rebuff from the bishops of Africa.45 But his indiscretion in this affair was of less importance than the ill-considered policy on which he embarked on a question of administration in the Gallic Church, and which proved highly embarrassing to his successors.
The authority which the Roman see exercised in western Europe at this time, beyond its prestige and acknowledged primacy in Christendom, was twofold. Decrees of Valentinian I and Gratian had recognised it as a court to which clergy condemned by provincial synods might appeal.46 In the second place it was looked up to as a model, and when doubtful questions arose about discipline it was consulted by provincial bishops. The answers of the Popes to such questions were known as Decretals. They did not bind the bishops; they were responses, not ordinances. Appellate jurisdiction and the moral weight of the Decretals were the principal bases on which the power of the Roman see was gradually to be built up.47
Zosimus entertained an idea of his authority which transcended these rights and anticipated the claims of his successors. Immediately after his election his ear was gained by Patroclus, the bishop of Arles, who desired to make his see an ecclesiastical metropolis of the first rank. In the three provinces of Viennensis, Narbonensis Prima, and Narbonensis Secunda, the bishops of Vienne, Narbonne, and Marseilles48 were the metropolitans; Arles was merely a bishopric in Narbonensis Prima. The idea of Patroclus was naturally enough suggested by the translation of the residence of the Praetorian Prefect of Gaul from Trier to Arles.49 Zosimus determined to deprive the bishops of Vienne, Narbonne, and Marseilles of their metropolitan rights, and to invest the bishop of Arles with jurisdiction over the three provinces. He also proposed to establish a new Metropolitan of Arles as a sort of Roman vicar, apparently over the whole of Gaul.50
The bishop of Narbonne yielded with a protest to this revolutionary assumption of sovranty. But the bishops of Marseilles and Vienne defied Zosimus and brought the question before a council of the Milanese diocese which met at Turin (Sept. 22, A.D. 417).51 The council at first decided against the pretensions of Arles, but finally compromised by dividing the Viennese province into two parts, of which the southern was to depend on Arles. Zosimus was not pleased, but deemed it prudent to concur. The bishop of Marseilles, who declined to yield, was excommunicated by a Roman synod, but remained quietly in his see. Thus a part of the Pope’s plan was actually carried out, but the facts remained that the council of Turin had refused to recognise the supreme authority of Rome, and that Marseilles had resisted with impunity.
The indiscretions of Zosimus were a lesson for his successors.52 Moreover, they recognised that the establishment of such a large and powerful see as that which Zosimus called into being was likely to be a rival rather than a vassal of Rome. Their aim was to undo what Zosimus had done, and in accomplishing this they acted with greater circumspection and increased the authority of their see. Both Boniface and Celestine53 did what they could to restrict the powers of the bishop of Arles. The first Narbonensis was withdrawn from his jurisdiction and restored to Narbonne.54 But the situation was more difficult for Rome, because the monks of Lérins, whose influence was strong in southern Gaul, threw the weight of their interest into the scale of Arles. Their founder, Honoratus, had been elected to succeed Patroclus, and he was followed by his disciple Hilary, whose authority threatened to usurp that of Rome in the Gallic Church.55 The conflict between Hilary and Leo I, who was elected in A.D. 440, is not edifying. An appeal to Rome (A.D. 444) gave the Pope a welcome opportunity of striking his opponent. He did not venture to excommunicate him, but he deprived him of the remnant of the province which Zosimus had created. This sentence could not be executed without the aid of the secular power. He had much influence with the Emperor and Galla Placidia, and he procured an edict, which was issued (July 8, A.D. 445) at the same time as his own decree.56 Arles was deprived of its metropolitan dignity.57
But that edict of Valentinian III did much more than settle in Rome’s favour this particular question. It assigned to the Roman see that supremacy over the provincial churches which the Popes had been endeavouring to establish, but which the African synods and the council of Turin had refused to acknowledge.58 It ordained that “the bishops of Gaul or any other province should take no decision contrary to the ancient rules of discipline without the consent and authority of the venerable Pope of the eternal city. They must conform to all the decrees of the Apostolic see. Bishops summoned before the tribunal of Rome must be compelled to appear by the civil authorities.”
It is the political bearing of this law that interests us here. When many of the western provinces had wholly or partly passed out of the Emperor’s control, it was a matter of importance to strive to keep alive the idea of the Empire and the old attachment to Rome in the minds of the provincials who were now subject to German masters. The day might come when it would be possible to recover some of these lost lands, which the Imperial government never acknowledged to be really lost, and in the meantime a close ecclesiastical unity presented itself as a powerful means for preserving the bonds of sentiment, which would then prove an indispensable help. To accustom the churches in Gaul and Britain, Spain and Africa to look up to Rome and refer their disputes and difficulties to the Roman bishop was a wise policy from the secular point of view, and it was doubtless principally by urging considerations of this nature that Leo was able to induce the government to establish the supremacy of his see.
It is important to bear in mind that the administrative authority of the Pope, at this time, extended into the dominions of the eastern Emperors. The lands included in the Prefecture of Illyricum belonged to the Patriarchate of Rome, and constituted the Vicariate of Thessalonica, where the Pope’s vicar, who was entrusted with the administration, resided. Theodosius II wished to place