'''Orthodox Christianity''' is the life in faith of the [[Orthodox Church]], inseparable from that concrete, historic community and encompassing its entire way of life. The Orthodox Christian faith is that faith "handed once to the saints" ([[Book of Jude|Jude]] 3), passed on in [[Holy Tradition]] to the [[apostles]] by [[Jesus Christ]], and then handed down from one generation to the next, without addition or subtraction.
The sole purpose of Orthodox Christianity is the salvation of every human person, uniting
us to Christ in the Church, transforming us in holiness, and imparting eternal life. This is the Gospel, the good news, that Jesus is the Messiah, that he rose from the dead, and that we may be saved as a result.
[[Image:Rublev Trinity.jpg|left|thumb|The [[Hospitality of Abraham]], an [[Old Testament]] pointer toward the [[Holy Trinity]].]]
''Main article: [[Holy Trinity]]''
Orthodox Christians worship the Father, Son, and Holy Spirit—the [[Holy Trinity]], the one God. Following the [[Holy Scriptures]] and the [[Church Fathers]], the Church believes that the Trinity is three divine persons (''[[
Hypostatic union|hypostases]]'') who share one essence (''ousia''). It is paradoxical to believe thus, but that is how God has revealed himself. All three persons are consubstantial with each other, that is, they are of one essence (''[[homoousios]]'') and coeternal. There never was a time when any of the persons of the Trinity did not exist. God is beyond and before time and yet acts within time, moving and speaking within history.
God is not an impersonal essence or mere "higher power," but rather each of the divine persons relates to mankind personally. Neither is God a simple name for three gods (i.e., polytheism), but rather the Orthodox faith is monotheist and yet [[Triadology|Trinitarian]]. The God of the Orthodox Christian Church is the God of [[Abraham]], [[Isaac]] and [[Jacob]], the '''I AM''' who revealed himself to [[Moses]] in the burning bush.
The source and unity of the Holy Trinity is the Father, from whom the Son is begotten and also from whom the Spirit proceeds. Thus, the Father is both the ground of unity of the Trinity and also of distinction. To try to comprehend unbegottenness (Father), begottenness (Son), or procession (Holy Spirit) leads to insanity, says the holy [[Gregory the Theologian]], and so the Church approaches God in divine mystery,
coming to know God [[apophatic theology|apophatically]] ; being content to encounter Him personally and yet realizing the inadequacy of the human mind to comprehend him.
The primary statement of what the Church believes about God is to be found in the [[Nicene-Constantinopolitan Creed]].
The Church is the Bride of Christ, the [[eschatology|eschatological]] spouse of the Son of God, united to him in faith and love, for which he gave himself up on the cross. The intimacy of a husband and wife is an earthly image of the intimacy that Christ has with his Church, and the union of an earthly marriage is a shadow of the union of that marriage of the Lamb of God with the Church.
The community of the Church is the locus of [[soteriology|salvation]] for mankind; it is truly the Ark in which mankind may be saved from the flood of corruption and sin. In it, Christians [[Holy Mysteries|sacramentally]] work out their salvation with fear and trembling ([[Philippians|Phil.]] 2:12), worshipping the Holy Trinity in spirit and in truth. The Church is the pillar and ground of truth ([[
I Timothy|I Tim.]] 3:15) and thus may be relied upon in the Christian's struggle to apprehend the one truth for himself. The Church is eternal, and the gates of [[Hell]] will never prevail against it ([[Gospel of Matthew|Matt.]] 16:18).
The Church consists of the [[prophet]]s and [[saint]]s of both the Old and New Covenants, the [[angels]] and the concrete, historical community of believers in this earthly life. Those who have gone on before us are known as the ''Church Triumphant'', while those in this life are known as the ''Church Militant''.
Unlike many conceptions of tradition in popular understanding, the Orthodox Church does not regard Holy Tradition as something which grows and expands over time, forming a collection of practices and doctrines which accrue, gradually becoming something more developed and eventually unrecognizable to the first Christians. Rather, Holy Tradition is that same faith which Christ taught to the Apostles and which they gave to their disciples, preserved in the whole Church and especially in its leadership through [[Apostolic succession]].
The central location in Holy Tradition is occupied by the [[Holy Scriptures]], the written witness to God's revelation in the Church. As such, the Scriptures are always [[hermeneutics|interpreted]] from within the Tradition which was the context for their writing and [[