When Cardinal Ratzinger was elected pope, taking the name Benedict XVI, the first words he spoke from the balcony of Saint Peter’s Basilica referred to his predecessor, Pope John Paul II, whom he referred to as “the great pope.” Since then, many have referred to him as “John Paul the Great.” Prior to that, only three popes came to be universally called “the Great”—Saint Gregory the Great (590–604), Saint Nicholas the Great (858–867), and the pope we honor today, Saint Leo the Great (440–461), who was the first pope to receive that title.
Leo was born in Tuscany, within the Western Roman Empire, at a time when the empire was experiencing decline due to ongoing threats of barbarian invasions, internal administrative disputes, and a difficult economic situation. Leo considered himself a Roman, since he spent his early years in the city. While still young, he was ordained a deacon in Rome under Pope Celestine and served him and his successor, Pope Sixtus III, in this capacity from 430–439. Deacons in Rome served the Church in important ways—as organizers of charitable works, liturgical services, and diplomatic missions; as administrators; and often as papal advisors. Deacon Leo quickly became highly respected in Rome as a man of unmatched theological learning and pastoral wisdom, prudence, and courage.
In 439, a dispute broke out in the northern part of the Roman Empire between a Roman prefect named Albinus and a prominent Roman general named Aetius. Seeing the need for a resolution so as to avoid internal conflict and even war, the Western Roman emperor asked the pope to send Deacon Leo to broker peace. While on the diplomatic mission, Pope Sixtus III died and the Roman clergy quickly chose Deacon Leo as the new pontiff. Word was sent to him, and he returned to Rome, was ordained a bishop on September 29, 440, and took charge of the keys of Saint Peter.
As the newly elected pope, Pope Leo wasted no time. At the heart of his mission was unity in the true faith, under the Vicar of Christ. At that time, papal primacy was not as clear as it is today. Not all supported the idea that the pope was the universal pastor and teacher of the faith, holding universal authority.
One way Pope Leo taught about papal primacy was by exercising it. When he became aware of heresies, he exercised discipline. He discovered that some clerics in Aquileia were holding on to the heresy of Pelagianism and instructed the bishop that they could not be admitted to communion unless they fully and publicly renounced their error. In Rome, when he discovered a sect of Manichæism, he sought the members out, engaged them in public debate, burned their books with the support of the civil authorities, and did all he could to purge them from the Church. When he learned that the heresy of Priscillianism was growing in Spain, he wrote at length to the Spanish bishops, pointing out the heresy, and advising them on ways to root it out. In all of this, Pope Leo began to emerge as “the” pope, not just one spiritual father among many others. He saw himself as the Vicar of Christ and acted as the Vicar of Christ, helping to further solidify this teaching of papal primacy.
