In the two-thousand-year history of the Church, only two popes enjoy the honorific “The Great,” according to Church tradition. The fifth century pontiff, St. Leo is one of them (his sixth century successor, Pope St. Gregory, is the other). Prior to his election as pope at the age of 40, St. Leo was already known as a great administrator and promoter of political peace. When conflicts broke out in Gaul, the Emperor sent St. Leo as his delegate to negotiate a peaceful resolution. As pope, he was able to use his considerable diplomatic skills to persuade Attila the Hun not to sack the city of Rome and, a few years later, Genseric the Vandal not to burn the city after pillaging it.
Along with the threat of military invasion, St. Leo also had to use his skill to confront the threats of heresy facing the Church – erroneous conceptions of the Faith such as Gnosticism, Pelagianism, Nestorianism, and others. Like all heresies, these tried to “solve” the mysteries of authentic Church teaching by proposing ideas that ultimately would have the effect of emptying the gospel of its significance and power. It was during St. Leo’s reign that the Council of Chalcedon (451) took place. Chalcedon was the fourth Ecumenical Council, following Nicaea (325), Constantinople (381), and Ephesus (431). The fruit of these four Councils was the firm establishment of orthodox Church teaching that all of its members must always and everywhere hold: that there is one God who is a communion of three Divine Persons, that Christ Jesus is the Second Divine Person of the Most Holy Trinity, equal to the Father in His divinity, with a true human nature that is like ours in every way but without sin.
In total, there have been 21 Ecumenical Councils, with the Second Vatican Council (1962-65) being the most recent. The early Councils, such as the ones mentioned above, tended to address the question: “Who is Jesus?” Most of the subsequent Councils addressed the question: “What is the Church?” The question that seems to be emerging in our age, and which was to a certain extent addressed at Vatican II, is: “What is Man?” Like the questions about the identity of Jesus that were settled by the early Councils, the question about what it means to be human have led people to come up with strange and harmful “solutions.” Among these “solutions” are those that suggest that we are ghosts in machines or walking pieces of meat, that consciousness and free will are illusions, that our actions have no significance beyond what we subjectively decide they mean, that we are the authors of our own reality. The widespread confusion that plagues our age, leading to innumerable conflicts, has its root precisely in the question of what it means to be human. In response, it’s helpful to turn to those early Church Councils and remember what they tell us about the identity of Christ. At least, this was something that the Second Vatican Council encouraged us to do, when it said: “Only in the mystery of the Incarnate Word does the mystery of man come to light” (Gaudium et Spes, 22). In other words, Christ Jesus reveals to us what it means to be truly human. Another great pontiff, St. John Paul II, seized upon this teaching of Vatican II and reminded us over and over again during his pontificate about the significance of human action, the meaning of the body, and the noblest end for which we are made – which is to become like God with the help of His grace. And so we see why it is crucial for us Catholics to learn our faith well. For we are called to bring clarity into the confusion by sharing with the world the wisdom of the Church, in order to help bring peace and reconciliation among peoples by sharing with each other the joy of friendship with Christ Jesus, who shows us what it means to be truly human.