With something more of apology (though with the precedent of his predecessors), he asserts his authority—"in order to prevent usurpations" in Illyria (Ep. v. i). As his predecessors had done, he appointed a vicegerent, Anastasius of Thessalonica, to whom he wishes the Illyrian bishops to submit as to himself. He is to be to the metropolitans as they are to the ordinary bishops, and a regular system of provincial administration is ordained, by which the assent of the papal vicarius is required for all episcopal elections and by which metropolitans are to be ordained actually by him (Ep. vi. 4; but cf. xiv. 6, where the latter point is modified). Biennial provincial councils, summoned by the metropolitans, referring graver matters to a representative synod, summoned by the vicar, whence again difficult questions are to be referred to Rome, are to maintain provincial discipline (Epp. xiv. 7; xiii. 2). Moreover, any individual bishop can appeal from the metropolitan directly to Rome, as Atticus, the metropolitan of Epirus Vetus, actually did some years later, securing the pope's interference against the cruel treatment of Anastasius (Ep. xiv. 1, p. 685). This supremacy of the papal vicar, which is of great historical importance, seems to have been accepted without remonstrance by the Illyrian churches (Ep. xiii. 1). Meanwhile, in 445, a letter from Dioscorus of Alexandria, probably announcing his succession to St. Cyril, gave Leo an opportunity of dictating to the church of Alexandria (Ep. ix.). That church owned St. Mark for her founder; should not the church of St. Mark be in complete accord with the church of St. Mark's master? On the strength of this relation between the churches, Leo gives Dioscorus detailed directions about days of ordination and the celebration of mass. About the same time the restless energy of Leo was engaged in his famous controversy with St. Hilary of Arles. This controversy (for which see HILARY), which is of special importance as being the first case in which "the supremacy of the Roman see over Gaul was brought to the issue of direct assertion on the pope's part, of inflexible resistance on the part of his opponent," arose out of an appeal of a bishop, Celidonius, to Rome against the judgment of Hilary. Though some blame attaches to Hilary, Leo's conduct was imperious, precipitate, unjust, and not over-scrupulous. The temptation to press a disputed claim of the Roman see and extend the Roman prerogative was too strong; Leo's violent language about the saintly Hilary (Ep. x.), his high-handed treatment of Gallic rights, and his attempt to give a sort of primacy in Gaul to Leontius on the mere score of age cannot be defended. He seems conscious that he is treading on doubtful ground in the beginning of his letter to the Gallic bishops, for he is careful to assert that there is nothing new in his proceedings, and that he is only defending the Gallic bishops from the aggressions of Hilary. He professes to consult them (c. 4); he fortifies himself with an imperial edict, for which he must be held mainly responsible (vid. sup.); though he apparently excluded Hilary from his communion, he did not venture to depose him from his episcopal functions, and on his death speaks of him as "sanctae memoriae" (Ep. xl.; cf. Tillem. xv. 80, 89). The peremptory orders of Leo seem to have obtained but inadequate execution in Gaul (Tillem. xv. 86) as shown in the election of Ravennius, Hilary's successor. Leo had desired (Ep. lxvi. 2) that the privileges he took from Hilary should be given to the bp. of Vienne; but the latter seems to have taken no part in the consecration of Ravennius, yet Leo speaks of his consecration as constitutionally conducted and divinely inspired (Epp. xl. xli.) and appears in the directions he gives Ravennius to recognize him as a metropolitan (Ep. xlii.; Tillem. xv. 93). Of the way Ravennius was consecrated, the bp. of Vienne seems to have made no complaint. He did, however, complain of the ordination by Ravennius of a bp. of Vaison (Ep. lxvi. 1). This complaint was followed on the other side by a petition from 19 bishops of the three provinces formerly subject to Arles, asking for the restoration to that see of its former dignity. Leo had now an opportunity to mediate. However imperfectly subservient to Leo's wishes the Gallic church had hitherto been, the tone of this letter is sufficiently abject. The pope's authoritative attitude and the imperial edict had done their work. They simply put themselves in Leo's hands. They ground the claim of Arles on ancient custom, civil dignity, and specially on the fact that in Trophimus that town had had the first Gallic bishop, and Trophimus had been sent by St. Peter; they even claim for Arles a certain authority over all Gaul as the vicegerent of the Roman see. Having received this appeal, so satisfactory in its tone, and the counter-complaint from Vienne, Leo proceeded to divide the authority. He examined carefully, he says, the rival claims of Vienne and Arles, and ultimately assigned a limited authority over four churches to the bp. of Vienne, and the rest of the province of Vienne to Arles; of the claims of Arles to larger metropolitan rights, he says nothing (Ep. lxvi.). This decision seems to have been acquiesced in by Ravennius, but did not finally stop the disputes of the rival sees (Tillem. xv. 95, 96). Leo sent also his tome to Ravennius for distribution in Gaul and secret communications, "quae committenda litteris non fuerunt," by the mouth of the messengers.
Probably c. 446 we find Leo correcting some scandals and asserting his authority in the church of Africa, too weak and disorganized now, from the devastations of Genseric and the recently concluded war, to resist interference as in the days of Celestine. He had sent a representative to make inquiries into alleged violations of discipline there in the election of bishops; on receiving his report, Leo wrote (Ep. xii. to the bishops of Mauretania Caesariensis) assuming complete authority over the administration of their church. He even received an appeal from an African bishop, LUPICINUS, and reversed the decision of the African church in receiving him to communion.
In 447 we have seen Leo entering into the affairs of the church of Spain, distracted like the African with barbarian invasions, and dictating the course to be pursued against the Priscillianist heretics; and the same year he
