The Christian life is a life in Christ. It is more than a mere philosophy – it is the total love of God, from which springs love for our neighbor.
Christianity is not some sort of abstract teaching which is accepted by the mind and found by each person separately. To the contrary, Christianity is a life in which separate persons are so united among themselves that their unity can be likened to the unity of the Persons of the Holy Trinity.
“Let anyone who is searching for the true Church of Christ in the maze of what claims to be Orthodox bear this fact in mind: The Church as the Bride of Christ is clothed in much fine raiment, but she is robed in no more a beautiful vestment than this: That She has kept faith with the Holy Martyrs.  Not only the martyrs of the Roman Imperial era, and the New Martyrs of the Turkish Empire, but also with the Holy New Martyrs under Communism.”
The life of Christ the Savior presents the reader of the Holy Gospels with numerous great moments which fill the soul with some special sense of grandeur. But perhaps the greatest moment in the life of all mankind was that occasion when, in the darkness of a southern night, under the hanging arches of trees just turning green, through which heaven itself seemed to be looking at the sinful earth with twinkling stars, the Lord Jesus Christ, in His High Priestly prayer, proclaimed:
“Holy Father, keep through Thine own name those whom Thou hast given Me, that they may be one, as We are . . . Neither pray I for these alone, but for them also which shall believe on Me through their word; That they all may be one; as Thou, Father, art in Me, and I in Thee, that they also may be one in Us” (John 17:11; 20-21).Special attention must be focused upon these words of Christ, for in them the essence of all Christianity is clearly defined. Christianity is not some sort of abstract teaching which is accepted by the mind and found by each person separately. To the contrary, Christianity is a life in which separate persons are so united among themselves that their unity can be likened to the unity of the Persons of the Holy Trinity. Christ did not pray only that His teaching be preserved so that it would spread throughout all the universe. He prayed for the unification of all those believing in Him. Christ prayed to His heavenly Father for the establishment, more correctly, for the restoration, on earth of the natural unity of all mankind. Mankind was created from one common origin and of one source (cf. Acts 17:26).

According to the words of Saint Basil the Great, “Mankind would not have had divisions, nor discord, nor wars if sin had not divided its nature”; and, “this is the main point of God’s saving economy of His incarnation – to bring human nature into unity with Himself and with the Savior. Then, having destroyed the evil part, to re-establish the original unity as the finest physician, through curative treatment, again mends the body which had been cut up in pieces.” The Church is formed of this unification of individuals; not of the apostles only, but of all those who believe in Christ according to their words. No earthly thing has ever been found which could be compared to the new community of saved people. There is no form of unity on earth with which one could compare the unity that is the Church. Such unity was found only in heaven. In heaven, the incomparable love of the Father, the Son and the Holy Spirit unites three Persons into one Being so that there are not three Beings, but One God living a triune life. Those people about whom Christ prayed to the heavenly Father: “that the love wherewith Thou hast loved Me may be in them, and I in them” (John 17:26) are also called to such a love which could fuse many into a state of oneness.

In the aforementioned words of Christ, the truth of the Church is placed into the tightest union with the mystery of the All-holy Trinity. People who enter the Church and love Her become like the three Persons of the Holy Trinity, whose love unites them into one being. The Church is like a one-essence of many persons, created by the moral beginning of love. This is precisely the theme which is perceived in the first sacred prayer of Christ the Savior by very many of the eminent fathers and teachers of the Church – Saint Cyprian of Carthage, Saint Basil the Great, Saint Gregory of Nyssa, Saint Ambrose of Milan, Saint Hilary of Poitiers, Saint Cyril of Alexandria, Saint Augustine of Hippo and Saint John Cassian. I have allowed myself to introduce short excerpts on this subject from the writings of some of this great and renowned assembly of fathers.

Saint Cyprian of Carthage, in his letter to Magnus, says: “The Lord, teaching us that unity comes from divine authority, affirms and says: “I and the Father are One” (John 10:30). In his composition “The Lord’s Prayer,” Cyprian also says: “Not being satisfied that He expiated us by His blood, He also interceded for us. While interceding for us, here is what He desired: that we will live in the very same state of unity in which the Father and the Son are one.”

Here is what Saint Cyril of Alexandria writes: “Christ, having taken as an example and image of that indivisible love, accord and unity which is conceivable only in unanimity, the unity of essence which the Father has with Him and which He, in turn, has with His Father, desires that we too should unite with each other; evidently in the same way as the consubstantial, Holy Trinity is united so that the whole body of the Church is conceived of as one, ascending in Christ through the fusion and union of two people into the composition of the new perfect whole. The image of Divine unity and the consubstantial nature of the Holy Trinity as a most perfect interpenetration must be reflected in the unity of the believers who are of one heart and mind.” Saint Cyril also points out “the natural unity by which we are all bound together, and all of us to God, cannot exist without bodily unity.”

All the earthly works of Christ, therefore, must not be thought of as teaching alone. Christ did not come to earth to announce some novel theoretical propositions to mankind. No! He came in order to create a completely new life for mankind, that is, the Church. Christ Himself said that He would build the Church (cf. Matt. 16:18).

This new human community, according to the conception of the Creator Himself, differs vitally from all other associations of people into various societies. Christ Himself often referred to His Church as the Kingdom of God and said that this Kingdom is not of the world, that is, its nature is not of the world, not temporal; it is not comparable with earthly kingdoms (cf. John 14:27; 15:19; 17:14-16; 18:36)

Christianity or the Church
by Saint Hilarion Troitsky