Catholic vs Orthodox: what is the difference?

Catholics and Orthodox Christians have more in common than almost any other two Christian bodies on earth. Both trace their origins to the apostles, both celebrate seven sacraments, and both preserve ancient forms of liturgical worship reaching back to the first centuries. The separation between them — known as the Great Schism of 1054 — was painful precisely because it divided communities that had shared one faith for a thousand years. Understanding what divides them, and what still unites them, requires looking honestly at history and theology alike.

The most significant doctrinal difference concerns the authority of the Bishop of Rome — the Pope. The Catholic Church teaches that the Pope, as successor of Saint Peter, holds 'full, supreme, and universal power over the whole Church, a power which he can always exercise unhindered' (CCC 882). This means that in matters of faith and morals, the Pope can speak with binding authority for all Catholics everywhere. The Orthodox Churches reject this claim to universal jurisdiction. They honour the Bishop of Rome as first among equals — a position of dignity and historic honour — but they do not accept that he holds a God-given right to govern the whole Church or to define doctrine unilaterally. Authority in the Orthodox world is instead shared among the ancient patriarchates (Constantinople, Alexandria, Antioch, Jerusalem, and others) acting collegially.

The second major theological difference is the filioque controversy. In the original Niceno-Constantinopolitan Creed (381 AD), Christians professed that the Holy Spirit 'proceeds from the Father.' Beginning in the Western church, the phrase 'and the Son' (filioque in Latin) was gradually added, so that the Creed read that the Spirit 'proceeds from the Father and the Son.' The Catholic Church defends this addition as doctrinally sound, teaching that the Spirit proceeds from both Father and Son as from a single principle (CCC 246). The Orthodox Churches regard the addition as both theologically erroneous and canonically illegitimate — a unilateral alteration of a creed that belonged to the whole Church. As the Catechism acknowledges, the introduction of the filioque into the Niceno-Constantinopolitan Creed by the Latin liturgy 'constitutes moreover, even today, a point of disagreement with the Orthodox Churches' (CCC 247).

Despite these divisions, the Catholic Church is explicit that what unites Catholics and Orthodox is profound and irreplaceable. Because the Orthodox Churches have preserved valid apostolic succession — an unbroken line of ordained bishops tracing back to the apostles — they possess true sacraments. The Catechism states: 'These Churches, although separated from us, yet possess true sacraments, above all — by apostolic succession — the priesthood and the Eucharist, whereby they are still joined to us in closest intimacy' (CCC 1399). This stands in sharp contrast to how the Church views ecclesial communities that emerged from the Protestant Reformation, which the Catechism teaches have not preserved the proper reality of the Eucharistic mystery in its fullness, especially because of the absence of the sacrament of Holy Orders (CCC 1400). With the Orthodox, the communion is so deep that the Catechism says it 'lacks little to attain the fullness that would permit a common celebration of the Lord's Eucharist' (CCC 838). The reason Catholics and Orthodox do not yet share Communion at one another's altars is not a statement of mutual contempt — it is a recognition that full visible unity has not yet been restored, and both churches long for that day.

There are also a number of secondary differences in practice and theology that developed over centuries of separate growth: different liturgical calendars (most Orthodox still use the Julian calendar for feast days), different approaches to icons and fasting, some differences in Marian theology (the Catholic dogma of the Immaculate Conception is not held in the same defined way by the Orthodox), and varying customs around married clergy (both East and West allow married men to be ordained priests, though bishops in the Orthodox tradition are almost always drawn from celibate monks). These differences are real but sit on top of a shared sacramental and doctrinal foundation that no other Christian tradition can claim.

For Catholics, the hope of reunion with the Orthodox is not a distant political aspiration — it is a prayer rooted in Christ's own words: 'That they may all be one' (John 17:21). The Catechism describes the desire to recover the unity of all Christians as 'a gift of Christ and a call of the Holy Spirit' (CCC 820). Both churches have been in ongoing theological dialogue for decades, seeking to resolve what centuries of estrangement created. If you would like to explore the Catholic faith more deeply, you can find a Catholic Mass near you, discover the lives of the saints venerated by both East and West, or learn about confession times at parishes in your area.