The Martyrdom of St. Andrew by Peter Paul RubensOsius was one of the most influential Church figures in Christian society at the time of Emperor Constantine and his two immediate successors.
St. Athanasius, his friend, called him on several occasions the great, the confessor of Christ, the venerable old man. The historian Eusebius of Caesarea says of him that Constantine considered him the most eminent Christian personage of his time.
Consecrated bishop of Cordoba in 295, he attended the Council of Elvira in 300 and, three years later, was confessor of the faith during the persecution of Maximian.
At the court of Constantine
From 312-313 he was at the court of Constantine as an adviser on religious matters. Eusebius of Caesarea says that the vision that Constantine had in dreams before the victory of the Milvian Bridge, was the one that determined him to call to his side the priests of that God, in whose sign it had been manifested to him that he would win. Their influence in the conversion of Constantine and his doctrinal instruction must have been decisive.
Between 312-325 Osius constantly accompanied the emperor's court. He must have inspired the Edict of Milan (which granted Christians complete freedom and the return of the buildings that had been confiscated from them and the ecclesiastical immunity granted to the clergy), the repeal of the Roman decree against celibacy, the edict aimed at the manumission of slaves in the Church and the authorization for Christian communities to receive donations and legacies.
St. Augustine, in his work against the Donatist Parmenianus, reminded the survivors of the Donatist heresy that, thanks to the bishop of Cordoba, the penalties against them had been less severe than could have been foreseen at first. At the Councils of Rome in 313 and Arles in 314, the Donatists had been condemned and their theory that the validity of the sacraments depended on the dignity of the minister had been rejected (the schism had arisen from the challenge to the ordination of Caecilian under the pretext that his consecrator Felix was a traditor - an accusation that later proved false - and that he had therefore lost the power of order).
The Donatists did not accept the decisions of the two councils and therefore the emperor intervened and in 316 declared Cecilian innocent and ordered to confiscate the churches to the Donatists. These measures had to be moderated in 321. Osius must have advised the emperor in these measures.
A Greek school that excessively cultivated exegesis and dialectics without due depth and a series of erroneous deductions led the Alexandrian priest Arius -the most genuine representative of that school- to affirm that the Son begotten by the Father could not have the same substance nor be eternal like Him.
Osius and St. Athanasius
In 324, Osius was sent by Constantine to Alexandria and was hosted by the bishop of Alexandria, Alexander. At that time the friendship between Osius and Athanasius, then deacon, began.
Osius, impressed by the gravity of the situation, since it was nothing less than the denial of the Divinity of the Word, returns to the court of Constantine (then in Nicomedia), convinced of the orthodoxy of the teachings of Bishop Alexander. It is likely that he advised Constantine to convene a Council.
Osius attended the Council of Nicaea, whose sessions he presided over, probably in the name of the Pope, with the Roman priests Vitus and Valens. According to St. Athanasius, Osius was largely responsible for the proposal to include the term homousion, consubstantial, in the Nicene Symbol. And not only that; St. Athanasius, eyewitness, expressly affirms that the redactor of the Nicene Creed was Osius.
In 343 he presided over the Council of Sardica, in which an attempt was made to return to the unity broken by the Arians. But these did not accept the peace proposals, almost all of which were aimed at avoiding ecclesiastical ambitions, and they withdrew from the council and declared Osius and Pope Julius I deposed.
Defender of the faith before Constantius
Constantius, son of Constantine, when his brother Constantius died in 350, began to apply in his dominions the religious policy already followed in the East, of frank sympathy towards the Arians. Two Arian bishops - Ursacius and Valens - induced Constantius to banish Pope Liberius and to attack Osius.
Constantius wrote to Osius ordering him to appear before him (the emperor was in Milan). Osius appeared before Constantius, who pestered him to communicate with the Arians and write against the Orthodox. But, as Athanasius wrote, the elder... rebuked Constantius and dissuaded him from his attempt, immediately returning to his homeland and his Church.
Later the emperor wrote to him again with threats, to which Osius replied with a letter in which, among other things, he said to Constantius: "I confessed Christ once, when your grandfather Maximianus aroused persecution. And if you persecute me, I am ready to suffer everything rather than shed innocent blood and be a traitor to the truth... Believe me, Constantius, to me, who by age could have been your grandfather... Why do you suffer Valens and Ursacius, who in a moment of repentance confessed in writing the calumny they had raised?
Fear the day of judgment and keep yourself pure for it. Do not meddle in the affairs of the Church nor command us in matters in which you are to be instructed by us. To you God gave the empire; to us he entrusted the Church. It is written: 'Render to Caesar the things that are Caesar's, and to God the things that are God's'. Therefore, it is not lawful for us to have dominion on earth, nor do you, O king, have power over holy things...".
Again the emperor intimated Osius to appear in his presence. The aged Osius set out on his journey and, about the summer of 356 or 357, arrived at Sirmium, where he met Constantius. Here Constantius confined him for a whole year, during which, according to the testimony of several Arians who composed Constantius' clique (Germinius, Ursacius, Valens, and Potamius, who were in Sirmium), Osius yielded to Arianism.
Death of Osio
St. Athanasius was then among the monks of Egypt and St. Hilary was exiled in the political diocese of Asia. In writings of these Fathers the idea, propagated by the Arians, is collected, which invites the suspicion that such writings were interpolated by Arians or their authors echoed what was said by the Arians who witnessed the events. In one of the writings of Athanasius, probably interpolated, it is said: "Constantius made so much force to the elder Osius and detained him so long at his side that, oppressed this one, he communicated with difficulty with the henchmen of Valensius and Ursacius, but he did not subscribe against Athanasius. But the old man did not forget this, for being about to die, he declared as in testament that he had been forced and anathematized the Arian heresy and exhorted that no one should receive it."
The name has been written in Latin, Hosius, derived, apparently, from the Greek Osios (saint), but the manuscript transmission gives Ossius, which leads to the Spanish form Osio.
Osius' whole life was concentrated on the defense of Catholic doctrine by word and action. This probably explains the scarcity of his literary production. We have preserved a beautiful letter full of integrity, addressed to Emperor Constantius in 354, of which some paragraphs have been reproduced above. According to St. Isidore, he also left an epistle to his sister in praise of virginity (De laude virginitatis) and a work on the interpretation of priestly vestments in the Old Testament (De interpretatione vestium sacerdotalium), which did not reach us.
His death must have taken place in the winter of 357/358. The Greek Church venerates him on August 27.
