Monastic Formation and Episcopate
Hilary entered the monastery of Lérins in his early youth, drawn there by his kinsman Honoratus, its abbot. The two were relatives, and one account holds that Hilary, originally raised outside the faith, converted and was baptized at Lérins after Honoratus's urging.
When Honoratus became bishop of Arles, Hilary served alongside him, and on Honoratus's death succeeded to the see around 429 despite his relative youth. As bishop he was known for his asceticism and preaching. Following the model of Augustine of Hippo, he organized his cathedral clergy into a common 'congregation,' devoting much of their life to shared ascetic discipline.
The Dispute with Rome
Hilary held the standing of a metropolitan and sought to exercise a primacy over the churches of southern Gaul, including oversight extending toward Vienne and Narbonne. In asserting this authority he deposed Chelidonius, bishop of Besançon, for disregarding his primacy.
The deposition was appealed to Rome. In 444 Pope Leo I used the case to abolish the Gallican vicariate that Hilary headed, stripping him of the rights to consecrate bishops, summon synods, and govern the province. Later tradition records that his zeal in spreading the faith brought him into conflict with the people and the civil authorities, and that he was more than once reproved from Rome; even so, his sanctity was not called into question.
Legacy and Veneration
After his death Hilary's name was introduced into the Roman martyrology, and he came to be venerated in both the Western and Eastern churches, with a feast on May 5. He is honored as the patron saint of Arles and is invoked against snake bites.
He is to be distinguished from the earlier Saint Hilary of Poitiers.
Works
Hilary's principal surviving work is the Vita Sancti Honorati, a biography and panegyric of his kinsman and predecessor Honoratus of Arles. He also composed the Metrum in Genesin, a versified treatment of Genesis.
A poem titled De providentia is sometimes attributed to him, though it is more commonly credited to Prosper of Aquitaine.
