One True Church? Part I
Updated: Jul 5
It is a self-denying ordinance to refrain from pronouncing any religious belief 'true'. The activities of Santa Claus are much more 'true', full of meaning and significance for human beings, than the reality of the dinner I had last night, which was certainly 'true' in an ordinary sense.
In the beginning, in the 1st century, the apostles established the three patriarchates [pate-tree-ar-kits] of Rome, Antioch, and Alexandria. Constantinople and Jerusalem were added by the 4th century. Only for the first thousand years was the church one. Scholars now estimate there are over 2600 groups today who lay claim to be the Church, or at least the direct descendants of the Church described in the New Testament. 
The five Patriarchal centers of this initial union, those indigenous to the Roman Empire, were Jerusalem, Antioch, Rome, Alexandria, and Constantinople. They formed a cohesive whole and were in full communion with each other. There were seven ecumenical councils between 325 and 787 uniting the leaders of the Church. One of the more significant councils during this period was the Council of Chalcedon [cal-se-don] in 451. The Council of Chalcedon, the Fourth Ecumenical Council, declared that Jesus is one person in two natures, divine and human, hypostasis. Dyophysite or dyophysitism states that Christ is One Person and One Hypostasis in Two Natures. The Council of Chalcedon brought back Roman-Byzantine relations back from the brink of rupture.
Because of this hypostatic union. The second person of the Trinity, the Son, is God, and thus all divine attributes are properly predicated of Him. He did not cease to be God in the incarnation, and therefore, all divine attributes can continue to be properly predicated of Him. In the incarnation, the Son assumes an unfallen, true human nature, a true human body and soul, with all of the attributes proper to a true human nature. Since it is His human nature, everything true of it can also be properly predicated of the one person to whom it belongs. Jesus Christ is perfect in divinity and perfect in humanity. The two natures of Christ are united without confusion or change. The two natures of Christ are united without division or separation.
The Second Council of Ephesus 431 was convened to conduct proceedings again Nestorius. Nestorius was a bishop of Constantinople who committed contrary error in his depictions of the nature of Christ and refusing to use the term “theotokus” and recognize Mary as the Mother of God.
The Council of Chalcedon was convened, in part, to settle matters of monophysitism and miaphysitism. Monophysitism asserts that the person Jesus Christ has only one, divine nature rather that two natures, divine and human. Miaphysitism hold that Jesus, the Incarnate Word, is fully divine and fully human, in one physis, (one nature). Monophysite was eventually replaced with miaphysite.
Some of the key issues in agreement amongst the Church leaders at the Council of Chalcedon were God the Father, Jesus Christ the Son of God, and the Holy Spirit which is God's presence everywhere; that Jesus is able to be divine and human at the same time; the special status of Mary as the mother of God; and of the use of icons in worship. The Armenian Church broke with the imperial Church after this council. The great Council of Chalcedon was under the control of Roman emperor, Marcian, and his wife, Pulcheria. The Church of Antioch is the same church where Bishop Ignatius had first used the word 'Catholic'. Like Nicaea in 325, the council in 451 remains an important moment in the consolidation of Christian doctrine into a single package for much of the Church. It centered on a formula of compromise. It is a mistake to think the council settled everything leading up to the beginning of the second millennium. Eastern Christians hated the decisions of the Council of Chalcedon and decisions made there served as a catalyst for the schism in 1054.
After Chalcedon, more questions arose, and more questions continue to arise today, but Chalcedon has proven to be a necessary and important starting point for all who have followed. Followers of the ecclesiological resolutions of the Council of Chalcedon, the two natures (divine and human) of Christ in particular, can be referred to as Chalcedonian Christians of which embrace the majority of Christian denominations today. The Council of Chalcedon did not answer every possible question in its definition, but it provided boundaries within which those questions can be examined without falling into heresy. As Christians, we owe a debt of thanks to our brothers in Christ who have gone before and whose gifts were used by God to help the church find its way through dangerous theological controversy. Because of centuries of their work, we do not have to reinvent the theological wheel every generation.
In the late second century, the Church in Rome's predominant language was still Greek. Theologians Tertullian and Augustine were both natives of North Africa, not Italy.
The Church was unified until the 11th century. Then, in events culminating in 1054 CE, the Roman Patriarch (the Latin-rite) pulled away from the other four (the Byzantine-rite), pursuing his long-developing claim of universal headship of the Church. This was the East-West Schism of 1054 CE, forming the Roman Catholic and Eastern Orthodox Churches. During the second millennium, the Roman Catholic Church developed an intensely centralised concept of spiritual authority, The most significant differences between them are the Roman Catholic Church believes in the two natures (divine and human) of Jesus Christ. The Eastern Orthodox believes in the one nature of Christ. In addition, the Roman Catholic Church’s beliefs are neatly contained in a single-volume document known as the Catechism. The same is not true for the Eastern church. Roman Catholics and Orthodox disagree on the nature of the relationship of the Holy Spirit to the Father and the Son.
Today, nearly a thousand years later, the Eastern Orthodox Churches, the four Patriarchates [pate-tree-ar-kits], Constantinople, Alexandria, Antioch, and Jerusalem, remain intact and in full communion. They form the Eastern Orthodox Patriarchates and maintain the Orthodox apostolic faith of the inspired New Testament record. Every Church not using the Latin rite (the Catholic rites of worship) or in communion with Rome maybe called "Orthodox" or "Eastern Orthodox". For the Orthodox, salvation is achieved by Christ’s triumph over death in the Resurrection. As a result, Greek art, unlike Western art doesn’t fixate on the figure of the bleeding, crucified Christ.
The Eastern Christian Churches making up the Oriental Orthodox Churches adhere to Miaphysite Christology, rather than hypostatsis in the Roman Catholic Church and they are broadly part of the trinitarian Nicene Christian tradition shared by today’s mainstream churches
Religion in the Greek world was tolerant, there was no religious persecution. It was through the Romans, the strong and well-organized, the cruel and authoritative power, that Christianity developed and became a state religion. The terrors and massacres, the inquisitions, the persecutions of Christian by Christian, might never have come about if Greece and not Rome had prevailed.
 Diarmaid MacCullouch, Christianity, The First Three Thousand Years, p.11  Time Line of Church History has been reproduced with permission from Conciliar Press (c)Copyright 1988, (Concilliar Press; Second Edition 1989).<https://saintignatiuschurch.org/wp-content/uploads/2011/10/timeline.html>  CCC 467 and 468  An imperial church is a church associated with an empire. The first such church was the state church of the Roman Empire, as patronized and largely controlled by the Roman Emperors from the time of the transfer of the seat of government to Constantinople.  Marcian was butchered by a mob along with six of his clergy. Thought him a traitor to 25th Pope Dioscorus of Alexandria, who was deposed by the Council of Chalcedon  Keith A. Mathison, The Basics of Chalcedonian Christianity, Table Talk Magazine, <https://tabletalkmagazine.com/posts/the-basics-of-chalcedonian-christology-2019-11/>  Patriarchate is an ecclesiological term in Christianity, designating the office and jurisdiction of an ecclesiastical patriarch, the title of “patriarch” was created in 531 by Justinian.