He was born by the end of the fourth century, from Tuscan parents. He was in Gaul for a delicate diplomatic mission when, after pope Sixtus III’s death, when he was unanimously elected by the people to succeed him on the chair of Peter. On 29 September 440 he was consecrated as the bishop of Rome. Leo was a mighty personality; he lived in a critical epoch of transition, when the decline of the Roman Empire colossal organisation was to coincide with the advent of Christianity, on the one hand, and the irruption of barbarian civilisations, on the other. With equal energy and intelligence pope Leo the Great could face the danger of barbarian invasions and the menace of the Monophysite heresy that threatened the Church’s faith in the mystery of the Incarnation. Whereas he could contain the threat of Attila that hanged over Italy, three years later he had to be powerless witness of the sack of Rome by the soldieries of Alaric, king of the Goths (455). As to the doctrine, Leo’s battle in defence of a Christological theology affirming both the true humanity (against Nestorius) and the true divinity (against Eutyches) of the person of Christ, was ratified by the Council of Chalcedon (451): “Peter has spoken thus through Leo”, the Fathers exclaimed. Despite the restless and so hard fought time he lived in, the very peculiar style of this writer and orator has to be underlined for the admirable serenity and harmony he could express. He died in 461.