The Orthodox say they are the one Church Christ founded, unchanged since the apostles, and that Rome is the one that left. It is a serious claim from serious Christians. Here is the Catholic answer.
Short answer: The Orthodox Churches are true particular Churches with apostolic succession, the Eucharist, and the faith of the Fathers, and Catholics honor that. But the Catholic Church teaches that the one Church of Christ "subsists in" the Catholic Church, because Christ built His Church on St. Peter and gave it a visible center of unity in St. Peter's successor. What the Orthodox lack is not holiness or sacraments, but full communion with that center. Holy Scripture, the councils the Orthodox accept, and the Greek Fathers they venerate all point to that center.
Key verses on the one Church
- "upon this rock I will build my church" (Matthew 16:18)
- "I have prayed that your own faith may not fail" (Luke 22:32)
- "there will be one flock, one shepherd" (John 10:16)
- "so that they may all be one" (John 17:21)
- "the church of the living God, the pillar and foundation of truth" (1 Timothy 3:15)
Scripture quotations are from the New American Bible, Revised Edition (NABRE), © 2010, 1991, 1986, 1970 Confraternity of Christian Doctrine, Washington, D.C. Used by permission. All rights reserved.
What the Orthodox Believe
In The Orthodox Faith, the handbook series by Fr. Thomas Hopko published on the Orthodox Church in America's website, he writes: "There can only be one Church and not many." Its unity "is not brought about or established by any human authority or juridical power, but by God alone." And "Orthodox Christians believe that in the historical Orthodox Church there exists the full possibility of participating totally in the Church of God." Other Christian bodies have "formal obstacles" to unity, "(e.g., the papacy in the Roman Church)."
The same series explains the schism: "From the Eastern Orthodox perspective, however, the biggest single reason for the Great Schism was the reassertion of Papal claims to have jurisdictional authority over all the Churches of Christendom."
So both sides agree Christ founded one visible Church with bishops, sacraments, and the faith of the councils. The question is whether that Church has St. Peter's successor as its visible center.
What Catholics Actually Teach
Start with what we share. With the Orthodox Churches, "this communion is so profound 'that it lacks little to attain the fullness that would permit a common celebration of the Lord's Eucharist'" (CCC 838). They "possess true sacraments, above all by apostolic succession, the priesthood and the Eucharist" (Unitatis Redintegratio 15).
Then the claim. The Church of Christ "subsists in the Catholic Church, which is governed by the successor of Peter and by the Bishops in communion with him" (Lumen Gentium 8; see CCC 816). Churches that keep "apostolic succession and a valid Eucharist," as the Orthodox do, "are true particular Churches," in which "the Church of Christ is present and operative," though "they lack full communion with the Catholic Church, since they do not accept the Catholic doctrine of the Primacy" (Dominus Iesus 17).
What Catholics do not teach:
- That the Orthodox are not Christians or not a Church (Dominus Iesus 17), or that their sacraments are invalid (UR 15). Vatican II speaks of the "family ties of common faith and charity which ought to exist between sister Churches" (Unitatis Redintegratio 14).
- That Orthodox believers today are guilty of the schism. The Catechism says "one cannot charge with the sin of the separation those who at present are born into these communities" (CCC 818).
- That the pope rules the bishops as subjects. "The Bishop of Rome is a member of the 'College', and the Bishops are his brothers in the ministry" (Ut Unum Sint 95).
The Biblical Case
1. Christ founded one visible Church
Jesus said "my church," not churches (Matthew 16:18). He promised "one flock, one shepherd" (John 10:16) and prayed "that they may all be one" (John 17:21). The Church is visible enough that a dispute can be brought to it: "tell the church" (Matthew 18:17). Catholics and Orthodox agree on all of this.
2. Christ built that Church on St. Peter
To St. Peter alone Jesus said, "upon this rock I will build my church," and "I will give you the keys to the kingdom of heaven" (Matthew 16:18–19). The keys recall the royal steward: "I will place the key of the House of David on his shoulder" (Isaiah 22:22), an office God took from Shebna and gave to his successor Eliakim (Isaiah 22:15–21). An office with keys has successors. And Jesus prayed for St. Peter: "your own faith may not fail; and once you have turned back, you must strengthen your brothers" (Luke 22:32). St. John Chrysostom, whose Divine Liturgy the Orthodox celebrate every Sunday, says that in John 21 "Jesus puts into his hands the chief authority among the brethren" (Homily 88 on John 1). Full case: Is the Papacy in the Bible?
3. The Church must be able to speak as one
In Acts 15, "The apostles and the presbyters met together," St. Peter rose to speak, and they decided: "It is the decision of the holy Spirit and of us" (Acts 15:6–7, 28). Its decisions were then handed on "to the people for observance" (Acts 16:4). Christ binds Himself to that voice: "Whoever listens to you listens to me" (Luke 10:16), and "whatever you bind on earth shall be bound in heaven" (Matthew 18:18). The Church is "the pillar and foundation of truth" (1 Timothy 3:15).
Here the Orthodox face a real difficulty. They accept seven ecumenical councils, the last in 787. In 2016 a Holy and Great Council met in Crete, but four autocephalous Churches, including the Russian Orthodox Church, did not attend. In 2018 the Russian Church broke communion with the Ecumenical Patriarchate over Ukraine. We say this with sorrow, not to score points; Catholics have their own sins. But when Orthodox Churches disagree, who can speak for the whole Church? The Catholic answer is St. Peter's successor: "there never is an ecumenical council which is not confirmed or at least recognized as such by Peter's successor" (CCC 884).
Objections Answered
(a) "Christ alone is the head of the Church. Rome had only a primacy of honor."
At its strongest: "He is the head of the body, the church" (Colossians 1:18). The Orthodox read the early canons as giving each bishop authority in his own territory, with Rome first in honor among equals. When Pope St. Victor I tried to cut off the Churches of Asia over the date of Easter around AD 190, St. Irenaeus admonished him. Hopko adds that the Church's unity "is not brought about or established by any human authority or juridical power, but by God alone."
Answer: Christ is the head, and St. Peter himself calls Him "the chief Shepherd" (1 Peter 5:4) while shepherding under Him. Christ is the one foundation (1 Corinthians 3:11), yet the Church is "built upon the foundation of the apostles and prophets" (Ephesians 2:20). A visible shepherd under Christ no more rivals Christ than an Orthodox bishop does. Unity is God's work, but God works it through men He appoints: "Whoever listens to you listens to me" (Luke 10:16). And St. Irenaeus, who admonished St. Victor, also wrote that "every Church should agree with this Church, on account of its preeminent authority." Honor alone does not explain what Eastern councils said to Rome (see below).
(b) "Rome changed the faith; the Orthodox kept it unchanged."
At its strongest: Rome added the filioque to the Creed and later defined the Immaculate Conception (1854), papal infallibility (1870), and the Assumption (1950) without the East. The Orthodox see themselves as guardians of the faith of the seven councils.
Answer: Scripture expects growth in understanding: the Spirit "will guide you to all truth," because Jesus had "much more to tell you, but you cannot bear it now" (John 16:12–13). The question is whether a teaching is growth or alteration. St. Vincent of Lérins, a fifth-century monk, taught that there is progress in the Church, "Yet on condition that it be real progress, not alteration of the faith," growing "in the same doctrine, in the same sense, and in the same meaning" (Commonitorium 23.54). The Orthodox accept such growth too: Nicaea's "consubstantial" is not a word found in Scripture. On the filioque, the Catechism calls the Eastern "through the Son" and the Western "and the Son" a "legitimate complementarity" (CCC 248). And the filioque is not a Latin novelty: Tertullian already wrote that he believed "the Spirit to proceed from no other source than from the Father through the Son" (Against Praxeas 4). Catholics hold that each later dogma passes St. Vincent's test, and that the Orthodox, who also pray for the dead and venerate the Theotokos as all-holy, already hold much of what Rome later defined. See The Filioque.
(c) "Rome is the one that broke from the ancient Church."
At its strongest: The Orthodox point out that the four other ancient patriarchates (Constantinople, Alexandria, Antioch, Jerusalem) remained together while Rome stood alone in 1054. The Church, they argue, is the communion of the patriarchs, and Rome left it.
Answer: Scripture does not make the Church's unity a matter of counting sees. Christ prayed for one man so that he would "strengthen your brothers" (Luke 22:32), and built on one rock (Matthew 16:18). The first millennium repeatedly saw Eastern patriarchs out of communion with Rome, and the East itself later judged Rome to have been right: the Third Council of Constantinople anathematized Sergius, "at one time patriarch of this royal god-protected city," with the other Monothelites, and praised Pope St. Agatho, telling the emperor that "Peter spoke through Agatho" (Session XIII; Prosphoneticus to the Emperor). St. Maximus the Confessor, who held out against those Eastern sees, said that all the Churches "have held and hold the great Church that is here [at Rome] to be their only basis and foundation" (CCC 834). The test of which side kept the faith was never which side had more patriarchs. It was communion with St. Peter.
The Early Church Agrees
- St. Ignatius of Antioch (Letter to the Romans, salutation, c. AD 110), an Eastern bishop on his way to martyrdom, greets the Church "which also presides in the place of the region of the Romans" and "which presides over love" (newadvent.org).
- St. Irenaeus of Lyons (Against Heresies 3.3.2, c. AD 180), raised in Asia Minor: "it is a matter of necessity that every Church should agree with this Church, on account of its preeminent authority".
- Council of Ephesus (AD 431), the papal legate Philip: St. Peter "received the keys of the kingdom from our Lord Jesus Christ" and "down even to today and forever both lives and judges in his successors."
- Council of Chalcedon (AD 451), after Pope St. Leo the Great's letter was read: "Peter has spoken thus through Leo."
- Third Council of Constantinople (AD 681), to Pope St. Agatho: "Therefore to thee, as to the bishop of the first see of the Universal Church, we leave what must be done" (Letter of the Council to St. Agatho).
Conclusion
The Orthodox Churches have kept the apostolic faith, the sacraments, and a liturgy of breathtaking beauty through centuries of persecution. Our disagreement is about one thing above all: St. Peter.
If you are Orthodox, we do not ask you to become Latin; the Eastern Catholic Churches show that full communion with Rome can keep Eastern liturgy and law (see Are Eastern Catholic Churches Really Catholic?). Pope St. John Paul II asked for help "to find a way of exercising the primacy which, while in no way renouncing what is essential to its mission, is nonetheless open to a new situation" (Ut Unum Sint 95). We ask you to consider whether the St. Peter honored by the councils you accept is Christ's gift to make us one.
Come home. That gift still has a name and a see, and the communion it makes possible is found in the Catholic Church. You already possess true sacraments and much of the apostolic faith, in "a certain, although imperfect, communion with the Catholic Church" (CCC 838). Those gifts draw their power "from the fullness of grace and truth that Christ has entrusted to the Catholic Church" and "are in themselves calls to 'Catholic unity'" (CCC 819). The Eucharist is the sacrament of the Church's unity, yet your true Eucharist is celebrated apart from the successor of St. Peter, on whom Christ built His Church (Matthew 16:18). We invite you into full communion with St. Peter's successor, the bishop of Rome, in the Catholic Church.
Your next step: Come to Mass or Divine Liturgy at your local Catholic church. You can find one near you at MassTimes.org. When you're ready, call the parish office and ask to speak with the priest about entering full communion with the Catholic Church. Read our guide: How Do I Become Catholic? Not ready yet? Get our free pocket guide below and keep learning.
FAQ
Does the Catholic Church call the Orthodox Church a true Church? Yes. Churches with "apostolic succession and a valid Eucharist," like the Orthodox, "are true particular Churches," though they lack full communion because they do not accept the primacy (Dominus Iesus 17).
Can Orthodox Christians be saved? The Church is "joined in many ways" to them (CCC 838), and those raised in these Churches cannot be charged with the sin of separation (CCC 818). But "all salvation comes from Christ the Head through the Church which is his Body" (CCC 846), and "it is through Christ's Catholic Church alone, which is the universal help toward salvation, that the fullness of the means of salvation can be obtained" (CCC 816). That is why we invite every Orthodox Christian into full communion. The warning of CCC 846 concerns those who, "knowing that the Catholic Church was founded as necessary by God through Christ, would refuse either to enter it or to remain in it."
What would reunion require? Agreement in faith, above all on the papacy, but not giving up Eastern liturgy or traditions. The Eastern Churches "have the power to govern themselves according to the disciplines proper to them" (UR 16).
Sources
Scripture (NABRE, bible.usccb.org): Isaiah 22:15–22; Matthew 16:18–19; Matthew 18:17–18; Luke 10:16; Luke 22:32; John 10:16; John 16:12–13; John 17:21; Acts 15:6–7, 28; Acts 16:4; 1 Corinthians 3:11; Ephesians 2:20; Colossians 1:18; 1 Timothy 3:15; 1 Peter 5:4.
Catechism of the Catholic Church (vatican.va): 248; 816, 818, 819, 834, 838, 846; 884.
Church documents (vatican.va): Second Vatican Council, Lumen Gentium 8; Second Vatican Council, Unitatis Redintegratio 14, 15, 16; Congregation for the Doctrine of the Faith, Dominus Iesus 17 (2000); Pope St. John Paul II, Ut Unum Sint 95 (1995).
Orthodox sources (oca.org): Thomas Hopko, The Orthodox Faith, vol. 1, "Church"; The Orthodox Faith, vol. 3, "The Great Schism".
Church Fathers and councils (newadvent.org unless noted): Ignatius of Antioch, Letter to the Romans; Irenaeus, Against Heresies 3.3.2; Tertullian, Against Praxeas 4; John Chrysostom, Homily 88 on John; Eusebius, Church History 5.24; Vincent of Lérins, Commonitorium 23 (ccel.org); Council of Ephesus (431), Session III; Council of Chalcedon (451), Session II; Third Council of Constantinople (681): Session XIII, Prosphoneticus to the Emperor and Letter of the Council to St. Agatho (ccel.org). Maximus the Confessor as quoted in CCC 834.
History: Wikipedia, "Pan-Orthodox Council" (Crete, June 2016; Antioch, Russia, Bulgaria, and Georgia absent); Wikipedia, "2018 Moscow–Constantinople schism".