The Eastern Orthodox Church, officially the Orthodox Catholic Church, and also called the Greek Orthodox Church or simply the Orthodox Church, is the second-largest Christian church, with approximately 230 million baptised members. It operates as a communion of autocephalous churches, each governed by its bishops via local synods. The church has no central doctrinal or governmental authority analogous to the head of the Catholic Church. Nevertheless, the Ecumenical Patriarch of Constantinople is recognised by them as primus inter pares, a title formerly given to the patriarch of Rome. As one of the oldest surviving religious institutions in the world, the Eastern Orthodox Church has played an especially prominent role in the history and culture of Eastern and Southeastern Europe.
Ultramontanism is a clerical political conception within the Catholic Church that places strong emphasis on the prerogatives and powers of the Pope. It contrasts with Gallicanism, the belief that popular civil authority—often represented by the monarch's or state's authority—over the Church is comparable to that of the Pope.
The highest-ranking bishops in Eastern Orthodoxy, Oriental Orthodoxy, the Catholic Church, the Hussite Church, Church of the East, and some Independent Catholic Churches are termed patriarchs.
The Eastern Catholic Churches or Oriental Catholic Churches, also called the Eastern-Rite Catholic Churches, Eastern Rite Catholicism, or simply the Eastern Churches, are 23 Eastern Christian autonomous particular churches of the Catholic Church, in full communion with the Pope in Rome. Although they are distinct theologically, liturgically, and historically from the Latin Church, they are all in full communion with it and with each other. Eastern Catholics are a minority within the Catholic Church; of the 1.3 billion Catholics in communion with the Pope, approximately 18 million are members of the eastern churches. The largest numbers of Eastern Catholics may be found in Eastern Europe, Eastern Africa, the Middle East, and India. As of 2022, the Syro-Malabar Church is the largest Eastern Catholic Church, followed by the Ukrainian Greek Catholic Church.
Traditionalist Catholicism is a movement that emphasizes beliefs, practices, customs, traditions, liturgical forms, devotions and presentations of teaching associated with the Catholic Church before the Second Vatican Council (1962–1965). Traditionalist Catholics particularly emphasize the Tridentine Mass, the Roman Rite liturgy largely replaced in general use by the post-Second Vatican Council Mass of Paul VI.
In Christian churches with episcopal polity, the rank of metropolitan bishop, or simply metropolitan, pertains to the diocesan bishop or archbishop of a metropolis.
The East–West Schism, also known as the Great Schism or the Schism of 1054, is the break of communion between the Roman Catholic and Eastern Orthodox churches since 1054. A series of ecclesiastical differences and theological disputes between the Greek East and Latin West preceded the formal split that occurred in 1054. Prominent among these were the procession of the Holy Spirit (Filioque), whether leavened or unleavened bread should be used in the Eucharist, iconoclasm, the coronation of Charlemagne as Emperor of the Romans in 800, the Pope's claim to universal jurisdiction, and the place of the See of Constantinople in relation to the pentarchy.
The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with 1.28 to 1.39 billion baptized Catholics worldwide as of 2024. It is among the world's oldest and largest international institutions and has played a prominent role in the history and development of Western civilization. The church consists of 24 sui iuris churches, including the Latin Church and 23 Eastern Catholic Churches, which comprise almost 3,500 dioceses and eparchies located around the world. The pope, who is the bishop of Rome, is the chief pastor of the church. The Diocese of Rome, known as the Holy See, is the central governing authority of the church. The administrative body of the Holy See, the Roman Curia, has its principal offices in Vatican City, a small independent city-state and enclave within the Italian capital city of Rome, of which the pope is head of state.
In Christian theology, ecclesiology is the study of the Church, the origins of Christianity, its relationship to Jesus, its role in salvation, its polity, its discipline, its eschatology, and its leadership.
Papal primacy, also known as the primacy of the bishop of Rome, is an ecclesiological doctrine in the Catholic Church concerning the respect and authority that is due to the pope from other bishops and their episcopal sees. While the doctrine is accepted at a fundamental level by both the Catholic Church and Eastern Orthodox Church, the two disagree on the nature of primacy.
College of Bishops, also known as the Ordo of Bishops, is a term used in the Catholic Church to denote the collection of those bishops who are in communion with the Pope. Under Canon Law, a college is a collection of persons united together for a common object so as to form one body. The Bishop of Rome is the head of the college.
The hierarchy of the Catholic Church consists of its bishops, priests, and deacons. In the ecclesiological sense of the term, "hierarchy" strictly means the "holy ordering" of the church, the Body of Christ, so to respect the diversity of gifts and ministries necessary for genuine unity.
Catholicity is a concept of pertaining to beliefs and practices that are widely accepted by numerous Christian denominations, most notably by those Christian denominations that describe themselves as catholic in accordance with the Four Marks of the Church, as expressed in the Nicene Creed formulated at the First Council of Constantinople in 381: "[I believe] in one, holy, catholic, and apostolic Church." The English adjective catholic is derived from the Ancient Greek adjective καθολικός, meaning "general", "universal". Thus, "catholic" means that in the Church the wholeness of the Christian faith, full and complete, all-embracing, and with nothing lacking, is proclaimed to all people without excluding any part of the faith or any class or group of people. An early definition for what is "catholic" was summarized in what is known as the Vincentian Canon in the 5th century Commonitory: "what has been believed everywhere, always, and by all."
Papal supremacy is the doctrine of the Catholic Church that the Pope, by reason of his office as Vicar of Christ, the visible source and foundation of the unity both of the bishops and of the whole company of the faithful, and as pastor of the entire Catholic Church, has full, supreme, and universal power over the whole church, a power which he can always exercise unhindered: that, in brief, "the Pope enjoys, by divine institution, supreme, full, immediate, and universal power in the care of souls."
The Catholic Church has engaged in the modern ecumenical movement especially since the Second Vatican Council (1962–1965) and the issuing of the decree Unitatis redintegratio and the declaration Dignitatis humanae. It was at the Council that the Pontifical Council for Promoting Christian Unity was created. Those outside of the Catholic Church were categorised as heretics or schismatics, but in many contexts today, to avoid offence, the euphemism "separated brethren" is used.
The Catholic Church and the Eastern Orthodox Church have been in a state of official schism from one another since the East–West Schism of 1054. This schism was caused by historical and language differences, and the ensuing theological differences between the Western and Eastern churches.
The East–West Schism that occurred in 1054 represents one of the most significant events in the history of Christianity. It includes various events and processes that led to the schism and also those events and processes that occurred as a result of the schism. Eastern and Western Christians had a history of differences and disagreements, some dating back to the period of Early Christianity. At the very root of what later became the Great Schism were several questions of pneumatology and ecclesiology. The most important theological difference occurred over various questions regarding the procession of the Holy Spirit, and the use of the filioque clause in the Nicene Creed. One of the main ecclesiological issues was the question of papal supremacy. Other points of difference were related to various liturgical, ritual, and disciplinary customs and practices. Some political and cultural processes also contributed to the breakout of the schism.
The historical roots of Papal primacy can be traced back to the early centuries of Christianity, wherein the bishop of Rome, commonly referred to as the Pope, gradually accrued increasing authority and recognition. A confluence of historical, theological, and political factors contributed to this development.
The Joint International Commission for Theological Dialogue Between the Catholic Church and the Eastern Orthodox Church was established by the Holy See and 14 autocephalous Orthodox churches.
The Eastern Orthodox Church is opposed to the Roman Catholic doctrine of papal supremacy. While not denying that primacy does exist for the Bishop of Rome, Eastern Orthodox Christians argue that the tradition of Rome's primacy in the early Church was not equivalent to the current doctrine of supremacy.
