First, we studied the apostolic communities that were part of the Catholic Church until the fifth century. Political difficulties, nationalism, and anti-imperial sentiment had as much to do with their separation from the rest of Christendom as theological controversy. The Church of the East, now called the Assyrian Church of the East, broke with the wider Christian communion after the Council of Ephesus (431) declared the Virgin Mary to be the Mother of God. This in response to Nestorius, the bishop of Constantinople (later deposed) who seemed to have held that there were two separate persons in Christ, one divine (the second Person of the Trinity) and the other human (the man Jesus); consequently, Nestorius thought it was nonsense to say that God was born, suffered, and died. The decree of Ephesus was meant to safeguard the unity of Christ’s human and divine natures. The Church of the East sided with Nestorius and went its own way. Nestorianism flourished, first in Syria, then in Persia – Nestorian missionaries even reached parts of distant India and China, and Nestorian Christianity became one of the major religions of Genghis Khan’s vast Mongol Empire.

Defining Jesus’ identity is a balancing act. If his humanity was separated from his divinity, one committed the heresy of Nestorianism; if it was crowded out by his divinity, one committed the opposite heresy, Monophysitism. In response to the latter, the fourth ecumenical council, held at Chalcedon in 451, proclaimed Christ to have two distinct natures – divine and human – united in the one divine Person of the Son. A great number of Christians, beginning with the Coptic Church in Egypt, refused to acknowledge the Council of Chalcedon and departed from Catholic unity. These “non-Chalcedonian” churches are collectively named Oriental Orthodox. While being in full communion with one another, they are hierarchically independent.

From the Assyrian and Oriental Orthodox churches, we turned our attention to the Orthodox Church of the East, a family of self-governing ethnic churches – Russian, Ukrainian, Serbian, Romanian, Greek, etc. – held together by a common faith and sacramental life. For nearly a millennium, the Eastern or Byzantine Church, centered on Constantinople, and the Western or Latin Church, centered on Rome, were two parts of a single communion. While the foundations of the faith were the same, doctrine was expressed differently in East and West. Deep disagreement over papal supremacy, worsened by mutual mistrust and mistreatment, eventually led to the tragic schism in 1054. How “Orthodox” became the proper name of the Eastern Church, it’s difficult to say. It was used at first by the Byzantines, not with any idea of opposition against the Latins, but rather as the antithesis to the Nestorians and Monophysites. Gradually, “Catholic” became the common name for the original Church in the West, “Orthodox” in the East.

The biggest share of our time was spent in Protestantism. It was necessary first to consider the causes and results of the sixteenth-century Reformation.  What the Reformation claimed to be espousing was not a new “Protestant” gospel but the faith of the true Church, the Catholic Church of all times, as against the false “papal” Church. The Reformers retained a great deal of historic Christianity: baptism in the name of the Trinity, Christ acknowledged as fully human yet fully divine, the Apostles’ and Nicene creeds, and, more fundamentally, the authoritative use of a collection of texts known as the Bible. However, many Protestants, disconnecting Scripture from the Church’s theological heritage and claiming the privilege of private interpretation, soon found it possible to discard infant baptism, sacramental realism, Marian devotion, and even Trinitarian orthodoxy.

After considering the origins and preoccupations of the chief branches of Protestantism – Lutheran, Reformed, Anglican, Anabaptist – we surveyed the myriad denominational families and their offshoots within the contemporary Protestant world. It’s no exaggeration to say that every emphasis spawned its own denomination, each one missing the forest for a few trees. In recent decades, many Protestants have tried to put together again those separate pieces that were pulled apart. The acceptance of grace through faith, the normativity of Scripture, the priesthood of all Christians – these Protestant “distinctives” can form part of the total life and teaching of the one Church. It’s a matter of combining them with the Catholic understanding of the Church both as the sacrament of Christ, mediating salvation through institutional means of grace, and as the communion of saints bound to Christ through time. To borrow an analogy from Peter Kreeft, the Church is not a melting pot but a stew; every ingredient is preserved in the mix of many differences, not melted down.

We may prayerfully hope that a day will come when all who profess faith in Christ will live in renewed, visible communion with one another. When the prayer of Jesus in John 17 is fulfilled, there will be but one sheepfold. Only God knows what the institutional form of Christian unity would look like. We can know that it will entail unity in the fullness of the truth that Christ intends for his Church, in Eucharistic celebration, and in communion with the continuing ministry of the Apostles. In a word, it will be catholic, embracing the totality of Christian experience and tradition. Catholicity is not the private domain of Catholicism, any more than orthodoxy is the private domain of Orthodoxy. Yet, as I hope to have shown, the dimensions and structures of catholicity have developed more robustly on the Catholic estate than anywhere else.

Father Kocik is a parochial vicar at Santo Christo Parish in Fall River.