Hilary was a native of Poitiers, France. He was an educated a pagan, and in his mid-30s he embraced Christianity, moved by the idea of G-d presented in the Holy Scriptures. Hilary soon converted his wife and daughter.
Hilary separated himself from all non-Catholic company and refused to eat with Jews or heretics, nor salute them by the way; but afterward, for their sake, he relaxed this severity.
He entered the Holy Orders, and in 353 was chosen as bishop of his native city Poitiers. Arianism was at its height of power, and St Hilary found himself called upon to support the orthodox cause in several Gallic councils in which Arian bishops formed an overwhelming majority. He was banished to Phrygia where he spent three years of exile. While in exile, he penned his great works on the Trinity.
In 359 he attended the Council of Seleucia, in which Arians, semi-Arians, and Catholics quarreled for the mastery. With the deputies of the council, he proceeded to Constantinople, and there so discouraged the heads of the Arian party that they prevailed upon the emperor to let him return to Gaul. He traversed Gaul, Italy, and Illyria, wherever he came discomfiting the heretics and procuring triumph of orthodoxy. After seven or eight years of missionary travel, he returned to Poitiers, where he died in peace in 368.
Reflection. Like St. Hilary, we, too, are called to a lifelong contest with heretics; we shall succeed in proportion as we combine hatred of heresy, with compassion for its victims.
Lives of the Saints, by Alban Butler, Benziger Bros. ed.