Hilaire de Poitiers, the first truly attested bishop of Poitiers, born around 315 and died in 367, is a Christian Latin writer. A theologian of the 4th century, he was a great defender of Nicene orthodoxy against Arianism and Sabellianism.
he was given the title of "Athanasius of the West" because of his energetic and pastoral action in the struggle for Christian orthodoxy. He was elevated to the rank of Doctor of the Church by Pope Pius IX in 1851. A saint for Christians, he is celebrated on 13 January.
Coming from the Gallo-Roman aristocracy of the city of Lemonum, he received a good education and was trained in Latin rhetoric. The autobiographical elements that are scattered throughout his works suggest that he was born a pagan, that he was converted through contact with the Bible,1 and that he was not baptized until around 345. He was a father of a family (including St. Abra), when he was elected bishop of the city around 350. Concerned about the instruction of his people, he wrote a Commentary on the Gospel of Matthew, which is the first Latin exegetical work that has come down to us. This text, a remarkable work of literal exegesis, shows, however, that Hilary does not know the Eastern tradition: his perception of the generation of the Word even shows that he is unaware of the formulations of the Council of Nicaea. In his later works, moreover, he admitted that he did not discover the Council of Nicaea until 354, nearly thirty years after this important meeting.
In 355, as Arianism spread to Gaul, he opposed this theology. In the Roman Empire of the mid-fourth century, it is also opposed to the emperor. During the Council of Béziers of 356, dominated by the Aryans united around Saturnin, the bishop of Arles, he was declared out of communion and exiled to Phrygia. It was there that he discovered the thought of the oriental theologians and wrote his great treatises on Trinitarian doctrine: de Trinitate, de Synodis.
Emperor Constantius II decided to convene simultaneously a Western Council in Rimini and an Eastern Council in Seleucia in order to reconcile the Church divided between Arian, Semi-Arian and Nicene. The Emperor wanted above all religious unity in order to achieve political unity.
Hilary seeks to expose Catholic doctrine to the Emperor in his two Books to Emperor Constance. He exposes his theses at the Council of Seleucia in 359, where he obtains the union of the Nicaeans, also called homoousians (because affirming the identity of substance between the Father and the Son), and of the Semi-Aryans, also called homoousians (because affirming the similarity of substance between the Father and the Son), against Arianism. But the Aryans were to convince the emperor of the veracity of their thesis, and the emperor promulgated a law which defined that the faith of the subjects of the Empire must be Arian.
Hilaire, for reasons that are unknown (according to the sources, it is either by grace of the new emperor Julian, or a new exile, because it is awkward in the East, or even a return without permission), returns to his city of Poitiers in 360-361. It is not known whether he was able to take part in the Council of Paris of January 361, but it clearly received his influence. Indeed, this regional council clearly condemned Arianism and dismissed the Arian bishops of Gaul.
Hilary, resuming his episcopal ministry, continues to write for the edification of his people, in particular his Treatise on the Mysteries, a mystagogical and allegorical catechesis, as well as his Commentaries on the Psalms, a work of exegesis. He continued his anti-ararian struggle, opposing in particular Auxence of Milan, with the help of Eusebius of Vercelli. He died in 367.