Archbishop, b. about 401; d. 5 May, 449. The exact place of his birth is not known. All that may be said is that he belonged to a notable family of Northern Gaul, of which in all probability also came St. Honoratus, his predecessor in the See of Arles. Learned and rich, Hilary had everything calculated to ensure success in the world, but he abandoned honours and riches at the urgent solicitations of Honoratus, accompanied him to the hermitage of Lérins, which the latter had founded, and gave himself up under the saint's direction to the practice of austerities and the study of Holy Scripture. When Honoratus, who had meanwhile become Archbishop of Arles, was at the point of death, Hilary went to his side and assisted at his latest moments. But as he was about to set out on his return to Lérins he was retained by force and proclaimed archbishop in the place of Honoratus. Obliged to yield to this constraint, he resolutely undertook the duties of his heavy charge, and assisted at the various councils held at Riez, Orange, Vaison, and Arles.
Subsequently began between him and Pope St. Leo the famous quarrel which constitutes one of the most curious phases of the history of the Gallican Church. A reunion of bishops, over which he presided in 444 and at which were present St. Eucherius of Lyons and St. Germain of Auxerre, deposed for incapacity provided against by the canons a certain Cheldonius. The latter hastened to Rome, was successful in pleading his cause before the pope, and consequently was reinstated in his see. Hilary then sought St. Leo in order to justify his course of action in the matter, but he was not well received by the sovereign pontiff and was obliged to return precipitately to Gaul. Several priests afterwards sent by him to Rome to explain his conduct met with no better success. Moreover, several persons who were hostile towards him profited by this juncture to bring various accusations against him at the Court of Rome, whereupon the pope excommunicated Hilary, transferred the prerogatives of his see to that of Fréjus, and caused the proclamation by the Emperor Valentinian III of that famous decree which freed the Church of Vienne from all dependence on that of Arles. Nevertheless there is every reason to believe that, the storm once passed, peace was rapidly restored between Hilary and Leo. We are too far removed from the epoch in which this memorable quarrel occurred, and the documents which might throw any light on it are too few to allow us to form a definitive judgment on its causes and consequences. It evidently arose from the fact that the respective rights of the Court of Rome and of the metropolitan were not sufficiently clearly established at that time, and that the right of appeal to the pope, among others, was not explicitly enough recognized. There exist a number of writings which are ascribed to St. Hilary, but they are far from being all authentic. Père Quesnel collected them all in an appendix to the work in which he has published the writings of St. Leo.