St Leo, Pope Leo I from 440 to 461, is one of only two pontiffs – the other is Gregory I (590-604) – who have been universally recognised as “the Great”.
It was indeed providential that, while the Roman Empire was falling to pieces, the Church was governed by a strong and able administrator who sustained, and indeed increased, the prestige of the papacy.
At the root of Leo’s thought was his passionate conviction that St Peter’s primacy, conferred by Christ Himself, lived on in every pope, bringing grace to all generations.
Since this power had not originated in this world, it could not be destroyed by this world. Leo understood, though, that this argument implied a unified Church. He therefore vigorously attacked the heresies of his time.
Among them, the Manichees represented the forces of evil as co-eternal with those of good. The Nestorians attacked the description of the Virgin Mary as the Mother of God. The Monophysites refused to accept Christ as at once both human and divine and the Pelagians held that man could achieve goodness by his own unaided will.
Leo stamped on all these perversions. He held, though, that, while the devil reigned in every challenge to orthodoxy he had set up his throne among the Manichees.
The pope’s theological views largely prevailed at the Council of Chalcedon in 451; and when some delegates resisted his will he simply declared their conclusions invalid. As his supporters observed: “Peter has spoken through the mouth of Leo.”
Ninety-six of Leo’s sermons and 143 of his letters have survived, demonstrating the clarity and economy of his style. In 1754 Benedict XIV recognised him as a Doctor of the Church, another distinction which he shares among popes only with Gregory the Great.
Leo sharply slapped down any bishop who disputed his authority. His letters of admonition reached errant subordinates in Africa, Gaul, Spain and Italy.
Equally, he established a commission to guard against any corruption of the papacy’s God-given mission. “If we do not watch with the vigilance which is incumbent upon us,” he declared, “we could not excuse ourselves to Him who willed that we should be the sentinel.”
Leo’s strength of personality was also evident in his confrontations with secular power. In 452 he encountered Attila the Hun near Mantua, and persuaded him not to proceed to the sack of Rome. Again, in 455, he met the Vandal Gaiseric outside the walls of Rome and succeeded in preventing the city’s wholesale destruction.
Little is known of Leo’s early life, save that he received a long training in papal administration under his predecessors, Celestine I (422-32) and Sixtus III (432-40). This most Roman of popes, however, seems to have been born into a Tuscan family.