What Is the Difference Between Catholic and Orthodox?

Same bishops, same Eucharist, same Fathers. So why are Catholics and Orthodox not one Church?

Short answer: Catholics and Orthodox share almost the entire faith, including valid sacraments and true apostolic succession. The Catholic Church says this communion "lacks little" of full unity. The main differences are the authority of the pope, the filioque in the Creed, purgatory, divorce and remarriage, and which councils are ecumenical. On each, Scripture gives the Catholic answer first, and the Fathers both Churches venerate confirm it.

Key verses on Catholic and Orthodox unity

• "so that they may all be one, as you, Father, are in me and I in you" (John 17:21)
• "upon this rock I will build my church" (Matthew 16:18)
• "and once you have turned back, you must strengthen your brothers" (Luke 22:32)
• "the Spirit of truth that proceeds from the Father" (John 15:26)
• "God sent the spirit of his Son into our hearts" (Galatians 4:6)
• "Thus he made atonement for the dead that they might be absolved from their sin." (2 Maccabees 12:46)
• "Therefore what God has joined together, no human being must separate." (Mark 10:9)

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 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). Vatican II taught: "These Churches, although separated from us, possess true sacraments, above all by apostolic succession, the priesthood and the Eucharist, whereby they are linked with us in closest intimacy" (Unitatis Redintegratio 15; see CCC 1399).

In 1965, Pope St. Paul VI and Ecumenical Patriarch Athenagoras I declared that they "commit these excommunications to oblivion," meaning those of 1054, while admitting this gesture "is not sufficient to end both old and more recent differences" (Joint Catholic-Orthodox Declaration).

What Catholics do not teach:

• That Orthodox sacraments are invalid (CCC 1399).
• That the Orthodox must become Latin. Eastern Catholic Churches keep their own liturgies in full communion with Rome. Vatican II itself speaks of the "family ties of common faith and charity which ought to exist between sister Churches" (Unitatis Redintegratio 14).
• That the pope rules alone. Christ formed the apostles as "a college or permanent assembly, at the head of which he placed Peter" (CCC 880).
• That the split was one side's fault. The Catechism admits that "often enough, men of both sides were to blame" (CCC 817).

The Biblical Case

1. Christ wants one visible flock

Jesus prayed "that they may all be one... that the world may believe that you sent me" (John 17:21). There is "one Lord, one faith, one baptism" (Ephesians 4:5).

2. The papacy

This is the central difference. The Orthodox honor St. Peter and grant Rome first place, as a primacy of honor among equals. Catholics hold that St. Peter received real authority over the whole Church. Jesus gave St. Peter alone the keys: "I will give you the keys to the kingdom of heaven" (Matthew 16:19). He prayed that St. Peter's "own faith may not fail" and told him, "you must strengthen your brothers" (Luke 22:32). He gave him the flock: "Feed my lambs," "Tend my sheep," "Feed my sheep" (John 21:15–17). So the pope "is the perpetual and visible source and foundation of the unity both of the bishops and of the whole company of the faithful" (CCC 882). Full case: Is the Papacy in the Bible?

3. The filioque

The Latin Creed says the Spirit "proceeds from the Father and the Son (filioque)" (CCC 246). The Orthodox object that this was added to the Creed and obscures the Father as the one source in the Trinity. Holy Scripture says the Spirit "proceeds from the Father" (John 15:26). But it also ties the Spirit to the Son: "he will take from what is mine," because "Everything that the Father has is mine" (John 16:14–15). He is "the spirit of his Son" (Galatians 4:6) and "the Spirit of Christ" (Romans 8:9).

Catholics do not deny the Father is the first origin. The East confesses that the Spirit "comes from the Father through the Son," and the Catechism calls the two ways of speaking a "legitimate complementarity, provided it does not become rigid" (CCC 248). But the doctrine itself is not optional. The Council of Florence, with Greek bishops signing, defined "that the holy Spirit is eternally from the Father and the Son" and that the explanation was "licitly and reasonably added to the creed" (Florence, Session 6). Full case: The Filioque: Does the Spirit Proceed from the Father and the Son?

4. Purgatory

Those who die "in God's grace and friendship, but still imperfectly purified," undergo purification "so as to achieve the holiness necessary to enter the joy of heaven" (CCC 1030). Judas Maccabeus "made atonement for the dead that they might be absolved from their sin" (2 Maccabees 12:46). A believer whose work burns up "will be saved, but only as through fire" (1 Corinthians 3:15). Jesus says one sin "will not be forgiven, either in this age or in the age to come" (Matthew 12:32), implying some forgiveness after death.

The Orthodox also pray for the departed in the Divine Liturgy, though many reject Latin terms such as purifying fire and satisfaction. The Catholic dogma is a real purification, "entirely different from the punishment of the damned" (CCC 1031). Florence defined that the souls of the truly penitent who die before making full satisfaction "are cleansed after death by cleansing pains," and that "the suffrages of the living faithful avail them" (Florence, Session 6). The terms are Latin; the substance is what the East already does every time it prays for the dead.

5. Marriage and divorce

Many Orthodox Churches permit a second and even a third marriage after divorce. The Orthodox Church in America states that the Church "does permit divorced individuals to marry a second and even a third time," with a rite that "bears a penitential character," performed by "economy" (OCA, "Divorce and Remarriage"). Their main scriptural appeal is Matthew 19:9: "whoever divorces his wife (unless the marriage is unlawful) and marries another commits adultery."

Our Lord's words are plain. "Therefore what God has joined together, no human being must separate." "Whoever divorces his wife and marries another commits adultery against her" (Mark 10:9, 11). "Everyone who divorces his wife and marries another commits adultery" (Luke 16:18). St. Paul passes on the same command, "not I, but the Lord," and says a separated wife "must either remain single or become reconciled to her husband" (1 Corinthians 7:10–11). Mark and Luke record no exception, and St. Paul hands on the Lord's command without one. The NABRE note on Matthew's clause reads it as an unlawful union from the start, so that it "constitutes no exception to the absolute prohibition of divorce when the marriage is lawful" (note on Matthew 5:31–32). Hence: "The Lord Jesus insisted on the original intention of the Creator who willed that marriage be indissoluble" (CCC 2382). The early Church agreed. The Shepherd of Hermas (second century) says a husband who puts away an adulterous wife must "remain by himself," and "if he put his wife away and marry another, he also commits adultery" (Commandment 4.1).

6. Councils

The Orthodox accept seven ecumenical councils, from Nicaea (325) to Nicaea II (787). Catholics accept these and later councils, including Trent and Vatican I and II. In Scripture, "The apostles and the presbyters met together to see about this matter" (Acts 15:6), St. Peter rose to speak (Acts 15:7), and they decided: "It is the decision of the holy Spirit and of us" (Acts 15:28). Nothing says that ability ended in 787. And "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) "In the first millennium, Rome had only a primacy of honor."

At its strongest: Eastern bishops sometimes resisted Rome, and papal infallibility and universal jurisdiction were defined at Vatican I in 1870, without the East.

Answer: Start with the Gospel. Satan "has demanded to sift all of you like wheat," but Christ prayed for St. Peter alone, so that he would "strengthen your brothers" (Luke 22:31–32). A first among equals who strengthens nobody is not what Jesus described. The early East recognized more than honor. At Ephesus (431), the papal legate declared that St. Peter "received the keys of the kingdom" and "down even to today and forever both lives and judges in his successors." At Chalcedon (451), after Pope St. Leo the Great's letter was read, the bishops cried, "Peter has spoken thus through Leo." And when the Sixth Ecumenical Council (Constantinople III, 680–681) received Pope St. Agatho's letter, the bishops told the emperor, "Peter spoke through Agatho" (Prosphoneticus to the Emperor). St. John Chrysostom, the Orthodox Church's own great preacher, says that in John 21 Jesus "puts into his hands the chief authority among the brethren" (Homily 88 on John 1). Vatican I defined what was already lived. Full case: Was the Pope's Primacy Recognized in the First Millennium?

(b) "Rome changed the Creed on its own."

At its strongest: The Creed of 381 has no filioque. The West added it to a shared creed without an ecumenical council of East and West.

Answer: Catholics grant that "The affirmation of the filioque does not appear in the Creed confessed in 381 at Constantinople" (CCC 247). The deeper question is whether it is true, and Scripture links the Spirit to the Son (John 16:14–15; Galatians 4:6). At the Council of Florence in 1439, Greek and Latin bishops agreed that "through the Son" and "and the Son" express the same faith: "All were aiming at the same meaning in different words" (Laetentur Caeli). The East later rejected that union, but the definition stands, and the gap can be bridged.

(c) "Purgatory is a Latin invention."

At its strongest: The Orthodox never adopted the word. At Florence, Mark of Ephesus rejected purifying fire after death, and legal language of "satisfaction" feels foreign to the East.

Answer: Scripture first: Judas Maccabeus "made atonement for the dead that they might be absolved from their sin" (2 Maccabees 12:46), and St. Paul speaks of one who "will be saved, but only as through fire" (1 Corinthians 3:15). If prayer and the Eucharistic sacrifice help the departed, the departed can still be helped. That is the heart of purgatory, and Eastern Fathers taught it (see below). The Church "formulated her doctrine of faith on Purgatory especially at the Councils of Florence and Trent" (CCC 1031), but the belief is ancient.

The Early Church Agrees

• St. Irenaeus of Lyons (Against Heresies 3.3.2, c. AD 180): "For 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: "There is no doubt, and in fact it has been known in all ages, that the holy and most blessed Peter, prince (ἔξαρχος) and head of the Apostles, pillar of the faith, and foundation (θεμέλιος) of the Catholic Church, received the keys of the kingdom from our Lord Jesus Christ".
• St. Cyril of Jerusalem (Catechetical Lecture 23.9, c. AD 350): we pray for the departed, "believing that it will be a very great benefit to the souls, for whom the supplication is put up, while that holy and most awful sacrifice is set forth."
• St. John Chrysostom (Homily 41 on 1 Corinthians 8, late fourth century): "For if the children of Job were purged by the sacrifice of their father, why do you doubt that when we too offer for the departed, some consolation arises to them?" And: "Let us not then be weary in giving aid to the departed, both by offering on their behalf and obtaining prayers for them".
• St. John Chrysostom (Homily 88 on John 1), on John 21: St. Peter "was the chosen one of the Apostles, the mouth of the disciples, the leader of the band".

Conclusion

Catholics and Orthodox are not strangers; we share "a certain, although imperfect, communion" (CCC 838). But the differences are real, and Christ willed one flock under the one He told to strengthen his brothers.

If you are Orthodox, we do not ask you to give up your liturgy or your saints. We ask you to consider whether the St. Peter of the Gospels, and the Rome that Ephesus and Chalcedon honored, still has a role today. And we pray with you for the day we share one altar again.

Come home. The Eucharist, the Fathers, and the apostolic succession that Catholics and Orthodox share all point to the unity Christ willed under St. Peter, and that unity 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

Are Orthodox sacraments valid? Yes. The Orthodox have true sacraments, above all the priesthood and the Eucharist (CCC 1399).

Can Catholics receive Communion in an Orthodox church? Normally, no. Catholics receive Communion at a Catholic Mass. Church law allows an exception only when all of these are true: it is "physically or morally impossible to approach a Catholic minister," "necessity requires it or true spiritual advantage suggests it," and "danger of error or of indifferentism is avoided" (Code of Canon Law, canon 844 §2). Convenience, curiosity, or a beautiful liturgy nearby does not qualify. And even then, the Orthodox Churches generally admit only their own members to Communion, so a Catholic should never approach without the Orthodox priest's consent. Respect their discipline. Where possible, ask your pastor first; your bishop may have local norms (canon 844 §5). The exception exists only because the Catholic Church recognizes that their Eucharist is real (CCC 1399).

Does an Orthodox Divine Liturgy fulfill a Catholic's Sunday obligation? No. The obligation is met by a Mass "celebrated anywhere in a Catholic rite either on the holy day or on the evening of the preceding day" (CCC 2180). Attending an Orthodox Divine Liturgy does not take the place of Sunday Mass.

When did Catholics and Orthodox split? Traditionally 1054, though the separation was gradual.

Sources

Scripture (NABRE, bible.usccb.org): 2 Maccabees 12:46; Matthew 12:32; Matthew 5:31–32 (with NABRE note); Matthew 16:18–19; Matthew 19:9; Mark 10:9, 11; Luke 16:18; Luke 22:31–32; John 15:26; John 16:14–15; John 17:21; John 21:15–17; Acts 15:6–7, 28; Romans 8:9; 1 Corinthians 3:15; 1 Corinthians 7:10–11; Galatians 4:6; Ephesians 4:5.

Catechism of the Catholic Church (vatican.va): 246, 247, 248; 817, 819, 838; 880, 882, 884; 1030, 1031; 1399; 2180; 2382.

Code of Canon Law (vatican.va): canon 844 §§2, 5.

Church documents (vatican.va): Second Vatican Council, Unitatis Redintegratio 14, 15; Pope St. Paul VI and Athenagoras I, Joint Catholic-Orthodox Declaration (December 7, 1965); Council of Florence, Laetentur Caeli (July 6, 1439); English text of Florence, Session 6: EWTN Library.

Orthodox sources: Orthodox Church in America, "Divorce and Remarriage".

Church Fathers and councils (newadvent.org): Shepherd of Hermas, Commandment 4.1; Irenaeus, Against Heresies 3.3.2; Council of Ephesus (431), Session III; Council of Chalcedon (451), Session II; Third Council of Constantinople (680–681), Prosphoneticus to the Emperor (ccel.org); Cyril of Jerusalem, Catechetical Lecture 23; John Chrysostom, Homily 41 on First Corinthians; John Chrysostom, Homily 88 on John.

History: Britannica, "Schism of 1054"; Britannica, "Ecumenical council"; Wikipedia, "East–West Schism".