Key terms of Orthodox theology, defined within the Church’s tradition and linked to where they appear in the corpus. These terms are also highlighted as you read.
The exact, strict observance of the Church's canons and rules. It stands in a balanced relationship with economia, by which the Church may, for the salvation of souls, apply a canon more leniently without abolishing the rule itself.
In the tradition: The Canons of the Church
The way of speaking about God by denial, affirming what God is not (not finite, not visible, not comprehensible), because His essence surpasses every created concept. It guards the divine transcendence and is held together with cataphatic (affirmative) theology.
In the tradition: Dionysius the Areopagite · Gregory of Nyssa · Maximus the Confessor
Spiritual training, the disciplined struggle of fasting, prayer, vigil, and watchfulness by which, with grace, a person is purified of the passions and grows toward God. It is not an end in itself but a means of healing and union with God.
In the tradition: John Climacus · The Desert Fathers · The Philokalia
The way of speaking about God by affirmation, naming Him from His revelation and works, as good, wise, living, light. It is true but always exceeded by God Himself, and so is balanced by apophatic (negative) theology.
In the tradition: Dionysius the Areopagite · John of Damascus
The state of a soul healed of the passions, in which its powers are rightly ordered and set free for the love of God and neighbor. It is not Stoic indifference or the absence of feeling but the restoration of the soul's health, whose crown is love.
In the tradition: Evagrius (received critically) · Maximus the Confessor · John Climacus
First, the whole "household management" of God for our salvation, above all the Incarnation and saving work of Christ. Second, in pastoral and canonical use, the Church's discretion to relax the strict letter of a canon for the good of souls, the complement of akribeia (strictness).
In the tradition: John Chrysostom · Maximus the Confessor
A distinction rooted in the Cappadocian Fathers and St. Maximus, and dogmatically clarified and defended by St. Gregory Palamas: God's essence remains forever beyond the creature's reach, yet God is genuinely present and participable through His uncreated energies, His grace, light, and operations. This lets the Fathers affirm both that God is incomprehensible and that we truly know and are united to Him.
In the tradition: Basil the Great · Maximus the Confessor · Gregory Palamas
The Latin addition of the words "and the Son" (Filioque) to the Nicene-Constantinopolitan Creed, so that the Holy Spirit is said to proceed from the Father "and the Son." The Orthodox Church confesses, with the Creed and the words of the Lord (John 15:26), that the Holy Spirit proceeds from the Father, and rejects the addition both as an unauthorized change to the conciliar Creed and as obscuring the Father as the one source within the Trinity.
In the tradition: Photius the Great · Mark of Ephesus · Gregory Palamas
From hesychia, "stillness," the contemplative tradition of guarding the heart and praying without ceasing, especially through the Jesus Prayer, that the nous may be united with the heart and the person illumined by grace. It was defended theologically by St. Gregory Palamas.
In the tradition: Gregory Palamas · The Philokalia · John Climacus
The whole life of the faith handed down in the Church by the Holy Spirit, in Scripture, the councils, the Fathers, the liturgy, the icons, and the lives of the saints. It is not a set of human customs added alongside Scripture but the living context within which Scripture itself is received and rightly understood.
In the tradition: Basil the Great · Irenaeus of Lyons
The term confessed at the First Council of Nicaea (325) to affirm that the Son is of the same essence as the Father, not a creature and not of a merely similar essence. It safeguards that the Word is truly and fully God, eternally begotten of the Father.
In the tradition: First Council of Nicaea · Athanasius the Great
The concrete, personal mode of existence of a being. In the doctrine of the Trinity, God is one essence (ousia) in three hypostases, the Father, the Son, and the Holy Spirit. In Christology, the divine Word is the one hypostasis in whom the divine and human natures are united.
In the tradition: Cappadocian Fathers · Council of Chalcedon
The union of full divinity and full humanity in the single Person (hypostasis) of the Word made flesh. The Council of Chalcedon confessed Christ in two natures "without confusion, without change, without division, without separation," each nature keeping its properties in the one Person.
In the tradition: Council of Chalcedon · Cyril of Alexandria · John of Damascus
The Orthodox honoring of holy icons, defined at the Seventh Ecumenical Council (Nicaea II, 787). Icons receive veneration (proskynesis), the honor of respect, which passes to the prototype, the person depicted, while worship (latreia) is given to God alone. Their making rests on the Incarnation: because the invisible God became visible in Christ, He may be depicted.
In the tradition: John of Damascus · Theodore the Studite · Seventh Ecumenical Council
The "self-emptying" by which the Son of God, without ceasing to be God, took the form of a servant and became man (Philippians 2:7). It names not a loss of divinity but the humility of God condescending to share our nature for our salvation.
In the tradition: Paul the Apostle · Cyril of Alexandria
The inner principles, purposes, or "words" according to which God creates and sustains each thing, all of which are contained in and refer back to the divine Logos, Christ. To contemplate the logoi is to see creation as God's, ordered toward Him. The teaching is developed especially by St. Maximus the Confessor.
In the tradition: Maximus the Confessor
Repentance, literally a "change of mind," understood not merely as regret but as an ongoing turning of the whole person away from sin and back toward God. It is the door of the spiritual life and is renewed continually.
In the tradition: John the Baptist · John Climacus
The highest faculty of the soul, often called the spiritual intellect or the eye of the heart, by which a person knows God directly, as distinct from discursive reasoning. In the ascetic tradition the nous is darkened by the passions and is purified and illumined through repentance and prayer.
In the tradition: Evagrius (received critically) · Maximus the Confessor · The Philokalia
What a thing is, its essence or substance. The three divine Persons share one and the same divine ousia, which is why they are one God and not three. The term is paired with hypostasis, which names not what God is but who each Person is.
In the tradition: First Council of Nicaea · Cappadocian Fathers
The disordered movements and impulses of the soul, such as gluttony, anger, vainglory, and pride, that distort our nature and are to be healed and transfigured rather than merely suppressed. (Distinct from Christ's Passion, His saving suffering.)
In the tradition: Evagrius (received critically) · Maximus the Confessor · John Climacus
The mutual indwelling and interpenetration of the three Persons of the Trinity, who dwell in one another in one undivided life and love. The term was first used of the two natures of Christ in His one Person and was later extended to the Trinity, above all by St. John of Damascus.
In the tradition: Gregory the Theologian · Maximus the Confessor · John of Damascus
The mind, outlook, or disposition that one acquires by living within the Church's tradition, the "mind of the Fathers." To have the Orthodox phronema is to think and discern from within the Church rather than merely to hold its conclusions as information.
In the tradition: The Fathers
The "active life" of keeping the commandments and ascetic struggle against the passions, which purifies the soul. In the spiritual tradition praxis is the necessary foundation for theoria, contemplation.
In the tradition: Maximus the Confessor · John Climacus
Spiritual delusion: a state of self-deception in which a person, often through pride or the enemy's influence, takes imagination or false experiences for the grace of God. The Fathers counsel humility, obedience, and sobriety as its remedy.
In the tradition: The Philokalia · Ignatius Brianchaninov
The cooperation between God's grace and the human person's free response in the work of salvation. Grace always goes first and accomplishes the work, yet it does not coerce; the person is called freely to assent and labor together with God.
In the tradition: John Cassian · Maximus the Confessor
The Mysteries (Baptism, Chrismation, the Eucharist, and the rest), the God-given actions of the Church in which, through visible things, the faithful truly receive the grace of the Holy Spirit. In Orthodox usage the term "Mystery" (the Greek behind the Latin "sacrament") is favored because it conveys that these realities transcend rational explanation and are not reducible to a defined mechanism.
In the tradition: Cyril of Jerusalem · Nicholas Cabasilas
Spiritual contemplation, the soul's vision of God and of the divine logoi in created things, which follows upon purification. In the Fathers it is the higher stage that praxis (ascetic practice) prepares the soul to receive as a gift of grace.
In the tradition: Maximus the Confessor · Evagrius (received critically)
The goal of the Christian life: that the human person, by grace, comes to share in the divine life and is united to God. The Fathers are careful that this is participation in God's uncreated energies, not in His essence, so the creature is truly joined to God without ceasing to be a creature or becoming God by nature.
In the tradition: Athanasius the Great · Maximus the Confessor · Gregory Palamas
"The one who gave birth to God," the title of the Virgin Mary confirmed at the Council of Ephesus (431). It is first a confession about Christ: because the one she bore is truly God and truly man in one Person, she is rightly called Mother of God.
In the tradition: Council of Ephesus · Cyril of Alexandria
In Orthodox understanding the grace that saves and deifies is not a created gift produced by God but God Himself, communicated through His uncreated energies. Because grace is God giving Himself, it can truly unite the creature to God without crossing into His unapproachable essence.
In the tradition: Gregory Palamas · Maximus the Confessor
Definitions explain the Church’s received vocabulary; they are not a substitute for the Fathers, the councils, or your priest. If you read something that seems off, tell us.