The Faith Once Delivered to the Saints

If you have ever walked into an Orthodox church and sensed something ancient, luminous, and alive, you were not imagining it. Orthodox Christianity is not a modern denomination or a reformed branch of something else. It is the original apostolic Faith, preserved whole and unbroken from the day of Pentecost to this very morning's Divine Liturgy.

Saint Jude urges believers to "contend earnestly for the faith which was once for all delivered to the saints" (Jude 1:3). That charge defines the Orthodox Church's entire self-understanding. She does not innovate; she guards, transmits, and lives the same Faith entrusted to the Apostles by Christ Himself.

This guide walks through the central beliefs of Orthodox Christianity—who God is, who Christ is, how we know divine truth, and what salvation actually means—so that whether you are a curious seeker or a lifelong parishioner, you can encounter these truths with fresh clarity.

God Has Spoken: Divine Revelation in Orthodoxy

Orthodox theology does not begin with human philosophy or abstract argument. It begins with the living God who chose to make Himself known. Revelation is not humanity reaching upward toward the divine; it is God reaching downward toward us in love.

The Church's daily Orthros (Matins) opens with the ancient proclamation drawn from Psalm 117(118):27: "God is the Lord and has revealed Himself to us." This is not a pious sentiment—it is a theological anchor. Everything the Orthodox Church believes rests on the fact that God is not silent and not hidden, but has freely disclosed Himself.

Saint Gregory the Theologian (Gregory of Nazianzus) taught that the divine essence itself remains forever beyond human comprehension, yet God genuinely communicates Himself through His energies—His grace, light, and life—so that we may truly know Him without exhausting Him. This distinction between the unknowable divine essence and the knowable divine energies, developed fully by Saint Gregory Palamas in the fourteenth century, is one of Orthodoxy's great theological gifts to the world.

The Holy Trinity: One God in Three Persons

The most fundamental Christian belief—shared by all historic Christians but understood with particular depth in Orthodoxy—is that God is Trinity: Father, Son, and Holy Spirit. One God, three distinct, co-equal, co-eternal Persons.

This is not a mathematical puzzle invented by councils. It is the Church's lived experience of God. The disciples encountered Jesus of Nazareth as fully divine. They received the Holy Spirit at Pentecost as a distinct Person, not merely a force. And they prayed to the Father as the source and fountain of the Godhead. The doctrine of the Trinity simply names what the Church had already experienced.

Saint Basil the Great wrote that the Holy Spirit is to be "numbered with the Father and the Son" and worshipped with the same honor, because the Spirit shares the same divine nature (On the Holy Spirit, 18). The Nicene Creed, ratified at the First and Second Ecumenical Councils (Nicaea 325 and Constantinople 381), enshrines this faith for all time.

Key Trinitarian Affirmations

  • One essence (ousia): Father, Son, and Spirit share one divine nature, not three separate gods.
  • Three hypostases (persons): Each Person is genuinely distinct—not merely a mask or a mode of the one God.
  • The Father is the eternal source and principle within the Trinity.
  • The Son is eternally begotten of the Father—not created, not lesser.
  • The Holy Spirit proceeds from the Father alone (John 15:26), a point on which Orthodoxy differs from Western Christianity's addition of the Filioque.
  • Equal glory: All three Persons receive the same worship and honor in every Orthodox liturgy.

The Incarnation: God Becomes Human

If the Trinity is the foundation of Orthodox theology, the Incarnation is its beating heart. The eternal Son of God—the second Person of the Trinity—took on complete human nature in the womb of the Virgin Mary and was born as Jesus of Nazareth. He is not a great moral teacher who was later elevated to divine status. He is God who became man.

Saint John's Gospel announces it with breathtaking brevity: "The Word became flesh and dwelt among us, and we beheld His glory" (John 1:14). Saint Athanasius of Alexandria, the great defender of Nicene orthodoxy, expressed the purpose of the Incarnation in words that have echoed through Orthodox theology ever since: "He became human so that we might become divine" (On the Incarnation, 54). This is the doctrine of theosis—divinization—and it is the goal of Orthodox Christian life.

What the Church Confesses About Christ

The Fourth Ecumenical Council at Chalcedon (451 AD) defined that Jesus Christ is one Person in two natures—divine and human—"without confusion, without change, without division, without separation." His divinity did not swallow His humanity, nor did His humanity diminish His divinity. He is the unique God-man, the only Mediator between God and humanity (1 Timothy 2:5).

Through His Death and Resurrection, Christ conquered sin and death—not merely as a legal transaction, but as a cosmic victory. He entered death and destroyed it from within. Every Paschal celebration in the Orthodox Church thunders this reality: "Christ is risen from the dead, trampling down death by death, and upon those in the tombs bestowing life."

Holy Scripture: The Written Word Within the Living Church

Orthodox Christians hold the Holy Scriptures in the highest reverence. A portion of the Bible is read at every single service of worship—at Vespers, Orthros, the Divine Liturgy, and all the other services of the liturgical cycle. The Church breathes Scripture.

The Orthodox Old Testament follows the Septuagint (LXX)—the Greek translation used by the Apostles themselves and quoted throughout the New Testament. It includes several books not found in the Hebrew Masoretic canon (such as Tobit, Judith, and the Wisdom of Solomon), which Western Protestants call the Apocrypha but which Orthodoxy regards as part of the canonical witness.

The New Testament—the four Gospels, the Acts of the Apostles, the Epistles, and the Book of Revelation—is the written record of God's perfect self-disclosure in Jesus Christ and the outpouring of the Holy Spirit in the early Church.

Scripture and the Church

Crucially, Orthodoxy does not treat the Bible as a self-interpreting book dropped from heaven. Scripture was written within the Church, by members of the Church, for the Church. The same Holy Spirit who inspired the biblical authors continues to guide the Church in understanding those texts. As Saint Peter writes, "No prophecy of Scripture is of any private interpretation" (2 Peter 1:20).

This means the Orthodox Church reads Scripture through the lens of the Church Fathers, the liturgical tradition, and the decisions of the Ecumenical Councils—not as a constraint on the text, but as the living context in which its full meaning is revealed.

Holy Tradition: The Living Memory of the Church

Holy Tradition is perhaps the most misunderstood aspect of Orthodox Christianity for those coming from Protestant backgrounds. Tradition is not a collection of human customs layered on top of the Bible. It is the very life of the Holy Spirit in the Church—the continuous, living transmission of the apostolic Faith across time.

Saint Paul himself commands: "Stand firm and hold to the traditions which you were taught, whether by word or by our letter" (2 Thessalonians 2:15). The written Scriptures are one expression of that Tradition—the most authoritative written expression—but they do not exhaust it.

What Holy Tradition Includes

  • The Holy Scriptures — the canonical books of the Old and New Testaments
  • The Nicene-Constantinopolitan Creed — the authoritative summary of apostolic faith
  • The Seven Ecumenical Councils — the Church's dogmatic definitions against heresy
  • The writings of the Church Fathers — the consensus of saintly theologians across the centuries
  • The Divine Liturgy and the other sacramental rites — worship as a vehicle of revealed truth (lex orandi, lex credendi)
  • The canons of the Church — the disciplinary and pastoral rules of the Councils
  • Holy icons — the theology of the Incarnation expressed in image and color
  • The lives of the Saints — living proof that the Faith produces genuine holiness

Together, these form a seamless whole. To receive Orthodoxy is not to accept a list of propositions; it is to enter a living community of faith that stretches back to the Upper Room and forward to the Kingdom of God.

The Seven Ecumenical Councils

When false teaching threatened to distort the apostolic Faith, the Church gathered her bishops from across the world in Ecumenical Councils to define—not create—what she had always believed. The Orthodox Church recognizes seven such councils as universally authoritative:

  1. Nicaea I (325): Affirmed the full divinity of the Son against Arianism; produced the original Nicene Creed.
  2. Constantinople I (381): Affirmed the full divinity of the Holy Spirit; completed the Nicene Creed.
  3. Ephesus (431): Declared Mary Theotokos (God-bearer), defending the unity of Christ's Person.
  4. Chalcedon (451): Defined Christ as one Person in two natures, against both Nestorianism and Monophysitism.
  5. Constantinople II (553): Clarified Chalcedonian Christology and condemned certain theological errors.
  6. Constantinople III (680–681): Affirmed that Christ has two wills—divine and human—against Monothelitism.
  7. Nicaea II (787): Restored the veneration of holy icons, affirming the reality of the Incarnation against Iconoclasm.

These councils did not impose new doctrines. They articulated, with precision and authority, what the Church had always confessed in her worship, her Scriptures, and her lived experience of God.

The Nicene Creed: The Symbol of Faith

The Nicene-Constantinopolitan Creed—recited at every Divine Liturgy and at Holy Baptism—is the Orthodox Church's authoritative summary of the apostolic Faith. It is called the Symbolon (Symbol of Faith) because it points beyond itself to the living reality it confesses.

"I believe in one God, Father Almighty, Maker of heaven and earth and of all things visible and invisible. And in one Lord Jesus Christ, the only-begotten Son of God, begotten of the Father before all ages. Light of Light, true God of true God, begotten not created, of one essence with the Father, through whom all things were made. For us and for our salvation He came down from heaven and was incarnate by the Holy Spirit and the Virgin Mary and became Man. He was crucified for us under Pontius Pilate, and He suffered and was buried. On the third day He rose according to the Scriptures. He ascended into heaven and is seated at the right hand of the Father. He will come again with glory to judge the living and the dead. His kingdom will have no end. And in the Holy Spirit, the Lord, Giver of Life, who proceeds from the Father, who together with the Father and the Son is worshipped and glorified, who spoke through the prophets. In one, holy, catholic, and apostolic Church. I acknowledge one baptism for the forgiveness of sins. I expect the resurrection of the dead and the life of the age to come. Amen."

Every phrase of this Creed was hammered out in the fire of theological controversy and sealed with the blood of martyrs. To recite it is to join your voice with every Orthodox Christian who has ever lived.

The Church: Body of Christ and Pillar of Truth

Orthodoxy does not recognize a separation between Christ and His Church. Saint Paul calls the Church "the body of Christ" (Ephesians 1:23) and "the pillar and ground of the truth" (1 Timothy 3:15). The Church is not a voluntary association of like-minded believers. She is the continuation of Christ's presence in the world, animated by the Holy Spirit.

This is why Orthodoxy insists that authentic Christian life is ecclesial—it is lived in the Church, not merely alongside it. Baptism incorporates a person into the Body of Christ. The Eucharist nourishes and unifies that Body. Confession heals the wounds of sin. Holy Chrismation seals the gift of the Holy Spirit. Marriage, Holy Orders, and Holy Unction—all the Mysteries (Sacraments) are encounters with the living God mediated through the Church's life.

The Holy Mysteries (Sacraments)

Orthodox Christians speak of Holy Mysteries rather than mere sacraments, because these rites are genuine encounters with divine grace—not symbols pointing to an absent reality, but vehicles through which the risen Christ acts in the lives of the faithful.

  • Holy Baptism: Death to the old self and resurrection into new life in Christ (Romans 6:3–4); the door into the Church.
  • Holy Chrismation (Confirmation): The personal Pentecost—the sealing of the Holy Spirit given immediately after Baptism.
  • The Divine Eucharist: The true Body and Blood of Christ under the forms of bread and wine; the center of Orthodox worship and the foretaste of the Kingdom.
  • Holy Confession (Repentance): The healing of the soul through sincere contrition and priestly absolution.
  • Holy Unction: Anointing with blessed oil for the healing of soul and body (James 5:14–15).
  • Holy Matrimony: The union of man and woman as an image of Christ's union with His Church.
  • Holy Orders: The ordination of bishops, priests, and deacons to serve the Body of Christ.

Theosis: The Goal of Orthodox Christian Life

Salvation in Orthodoxy is not merely a legal verdict pronounced over a guilty defendant. It is a transformation—a real participation in the divine life. This is theosis, or divinization: the process by which a human being, by grace, comes to share in the very life of the Holy Trinity.

Saint Peter speaks of believers becoming "partakers of the divine nature" (2 Peter 1:4). Saint Athanasius, Saint Basil, Saint Gregory of Nyssa, Saint Maximus the Confessor, and Saint Gregory Palamas all developed this theme with extraordinary depth. Theosis is not the absorption of the human person into God—our humanity is not dissolved—but its full flowering in union with Him.

The entire liturgical and ascetic life of the Church—fasting, prayer, almsgiving, the Mysteries, the reading of Scripture, the veneration of icons, and the pursuit of virtue—is ordered toward this one goal: that we might, by grace, become what Christ is by nature.

The Veneration of the Theotokos and the Saints

Orthodox Christians honor the Virgin Mary as Theotokos—God-bearer, or Mother of God—a title affirmed by the Third Ecumenical Council at Ephesus (431 AD). This title is not primarily about Mary herself; it is a Christological statement. If the one she bore is truly God, then she is truly the Mother of God.

The Saints are not distant historical figures. They are alive in Christ, members of the same Body, and powerful intercessors before the throne of God. When Orthodox Christians ask the Saints to pray for them, they are doing what any Christian does when asking a fellow believer for prayer—except that the Saints pray from within the fullness of God's presence.

Holy icons are not idols. They are windows into the heavenly realm, theological statements about the reality of the Incarnation, and reminders that the communion of saints surrounds us at every liturgy. The Seventh Ecumenical Council (Nicaea II, 787) definitively affirmed their proper veneration.

Frequently Asked Questions

Is Orthodox Christianity the same as Roman Catholicism?

No. While both traditions share apostolic succession, the seven Ecumenical Councils, and the ancient sacramental life, they separated in the Great Schism of 1054. Key differences include the Orthodox rejection of the Filioque addition to the Creed, papal infallibility and universal jurisdiction, and certain doctrines developed in the medieval West (such as purgatory and the Immaculate Conception). Orthodoxy views herself as the undivided Church of the first millennium, unchanged.

Do Orthodox Christians believe the Bible is inerrant?

Orthodox Christians affirm that the Holy Scriptures are divinely inspired and fully trustworthy as a witness to God's revelation. However, Orthodoxy does not typically use the Protestant framework of "inerrancy" or "sola scriptura." Scripture is read and interpreted within the living Tradition of the Church, guided by the Holy Spirit and the consensus of the Church Fathers.

What does the Orthodox Church teach about salvation?

Salvation is understood as healing, transformation, and union with God—not merely a legal acquittal. Through Christ's Death and Resurrection, the power of sin and death has been broken. Through the Holy Mysteries, prayer, fasting, and repentance, the faithful are progressively transformed into the likeness of Christ. This process, called theosis, is the goal of Orthodox Christian life.

Can non-Orthodox Christians attend an Orthodox service?

Non-Orthodox visitors are warmly welcomed to attend Orthodox services and observe the worship. However, only baptized and chrismated Orthodox Christians in good standing with the Church may receive Holy Communion. This practice of "closed communion" reflects the Orthodox understanding that the Eucharist is the expression of full unity in faith, not a means of achieving it.

Conclusion: An Invitation to the Ancient Faith

Orthodox Christianity is not a religion of rules and rituals for their own sake. It is a way of life—a participation in the very life of the Holy Trinity, made possible by the Incarnation, Death, and Resurrection of Jesus Christ, and sustained by the Holy Spirit in the life of the Church.

From the Nicene Creed to the Divine Liturgy, from the writings of Saint Athanasius to the icons of Saint Andrei Rublev, every element of Orthodox life points toward a single horizon: that we might know God, love Him, and be transformed into His likeness forever.

If these truths stir something in you, the next step is simple: find your nearest Orthodox parish, attend the Divine Liturgy, and let the ancient Faith speak for itself.

Further reading: Explore our guides on the Divine Liturgy, theosis and deification, and the Seven Holy Mysteries to go deeper into the Orthodox Faith.