Pope Leo I

Pope Leo I (Italian: Leone I) (c. 391 – 10 November 461), also known as Leo the Great (Latin: Leo Magnus; Italian: Leone Magno), was Bishop of Rome from 29 September 440 until his death on 10 November 461. He is the first of the three Popes listed in the Annuario Pontificio with the title "the Great", alongside Popes Gregory I and Nicholas I.

Leo was a Roman aristocrat. He is perhaps best known for meeting Attila the Hun in 452 and persuading him to turn back from his invasion of Italy, though how large a part his personal authority played is debated, and some argue that Attila was already ready to end his campaign.^{[citation needed]} He is also a Doctor of the Church, most remembered theologically for issuing the Tome of Leo, a document which was a major foundation to the debates of the Council of Chalcedon, the fourth ecumenical council. That meeting dealt primarily with Christology and elucidated the definition of Christ's being as the hypostatic union of two natures, divine and human, united in one person, "with neither confusion nor division". It was followed by a major schism associated with Monophysitism, Miaphysitism and Dyophysitism. He also contributed significantly to developing ideas of papal authority.

According to the Liber Pontificalis, he was a native of Tuscany and son of Quintianus or Quintilianus. By 431, as a deacon, he was sufficiently well known outside of Rome that John Cassian dedicated to him the treatise against Nestorius written at Leo's suggestion. About this time Cyril of Alexandria appealed to Rome regarding a jurisdictional dispute with Juvenal of Jerusalem, but it is not entirely clear whether the letter was intended for Leo in his capacity as archdeacon, or for Pope Celestine I directly.

Near the end of the reign of Pope Sixtus III, Leo was dispatched at the will of Emperor Valentinian III to settle a dispute between Aëtius, one of the chief Roman military commanders in Gaul, and the chief magistrate Albinus. Johann Peter Kirsch sees this commission as a proof of the confidence placed in the able deacon by the Imperial Court.

During Leo's absence in Gaul, Pope Sixtus III died on 11 August 440, and on 29 September Leo was unanimously elected by the people to succeed him. Soon after assuming the papal throne, Leo learned that in Aquileia, Pelagians were received into church communion without formal repudiation of their heresy; he censured this practice and directed that a provincial synod be held where such former Pelagians be required to make an unequivocal abjuration.

Leo claimed that Manichaeans, possibly fleeing Vandal Africa, had come to Rome and secretly organized there. In late 443, Leo preached a series of sermons condemning the Manichaeans and calling for Romans to denounce suspected heretics to their priests. Eventually, suspected heretics were brought to court, and likely under torture, they confessed to various crimes. By early 444, Leo announced to the bishops of Italy that the Manichaeans had been eradicated from Rome. According to his contemporary Prosper of Aquitaine, Leo exposed the Manichaeans and burned their books. He was equally firm against the Priscillianist sect. Bishop Turibius of Astorga, astonished at the spread of the sect in Spain, had addressed the other Spanish bishops on the subject, sending a copy of his letter to Leo, who took the opportunity to write an extended treatise (21 July 447) against the sect, examining its false teaching in detail and calling for a Spanish general council to investigate whether it had any adherents in the episcopate.

From a pastoral perspective, he energized charitable works in a Rome beset by famines, an influx of refugees, and poverty. He further associated the practice of fasting with charity and almsgiving, particularly on the occasion of the Quattuor tempora, (the quarterly Ember days). It was during Leo's papacy that the term "Pope", which previously meant any bishop, came to exclusively mean the Bishop of Rome.

Leo drew many learned men about him and chose Prosper of Aquitaine to act in some secretarial or notarial capacity. Leo was a significant contributor to the centralisation of spiritual authority within the Church and in reaffirming papal authority. In 450, the Byzantine Emperor Theodosius II, in a letter to Pope Leo I, was the first to call the Bishop of Rome the Patriarch of the West, a title that would continue to be used by the popes through the present days (only interrupted by a brief period between 2006 and 2024).