Christ Jesus is the savior of the world because in his divine person (hypostasis) he has united created nature and taken it through the crucible of death into a glorified eternal existence. John Zizioulas elaborates:
This victory is achieved in the Resurrection, without which there can be no talk of salvation, because death is the problem of creation. “If Christ has not been raised,” says St Paul, “your faith is in vain” (1 Cor. 15.14). Christ is “the Saviour of the world” not because he sacrificed himself on the Cross, thereby wiping away the sins of the world, but because “he is risen from the dead having trampled death by death.” The West (Catholic and Protestant) has viewed the problem of the world as a moral problem (transgression of a commandment and punishment) and has made of the Cross of Christ the epicentre of faith and worship. However, Orthodoxy continues to insist upon the Resurrection as the centre of its whole life precisely because it sees that the problem of the created is not moral but ontological; it is the problem of the existence (and not of the beauty) of the world, the problem of death. And the Resurrection of Christ was made powerful thanks to the union “without division” but also “without confusion” of the created and the uncreated; in other words, thanks to the love that makes the created and the uncreated surpass their limits and unite “without division,” and thanks to the freedom which means that the created and the uncreated do not lose their diversity by going beyond their limits in this union, but on the contrary preserve it, and so maintain their dialectical relationship. (Communion and Otherness, p. 261)
Mortal human beings can survive their created existence only by transcending themselves, going out of themselves in love and freely uniting themselves to an uncreated hypostasis. For this purpose God offers humanity the crucified and risen Christ.
The teaching of the fourth ecumenical council on the person of Jesus Christ, like the whole of patristic Christology, loses all meaning if it is not related to the problem of the created and the overcoming of death. If Christ is presented there as saviour of the world, it is not because he brought a model of morality or a teaching for humanity; it is because he himself incarnates the overcoming of death, because, in his own person, the created from now on lives eternally. (p. 259)
For the created to escape this destiny [of death], it needs a new birth, that is, a new way of being, a new hypostasis. It is not without reason that the Christology of Chalcedon insists on the fact that the hypostasis of Christ is that of the eternal Son in the holy Trinity; in other words, in the uncreated God, and not a human, that is, created, hypostasis. If the hypostasis of Christ had been created, death would have been just as fatal for him and victory over death impossible. The same goes for each human being. If our hypostasis is the one taken from our biological birth, then … freedom and love–those two constituents of existence—remain apart from one another and death follows. However, if only we can acquire a new hypostasis; in other words, if our personal identity, that which makes us persons, can spring from free relations which are loving and loving relations which are free, then our created nature, united without division and without confusion to the uncreated God, will be saved from its destiny of death. By means of Baptism, followed by the Eucharist, the Church offers us that possibility, because it gives us a new identity deeply rooted in a network of relationships which are not obligatory, like those which create the family and society, but free. (p. 263)
To be saved is to the incorporated into Jesus Christ. In union with the incarnate Son created beings are anchored within the uncreated God. In Christ they take on a new hypostasis, a new identity; in Christ they share the life of the Father, Son, and Holy Spirit. This theme is clearly found in the writings of both St Paul and St John the Theologian, but Zizioulas has recast it into the language of personal-relational ontology. Aristotle Papanikilaou explains:
What Christ offers for salvation for human existence, then, is not so much the divine energies as his own hypostasis. … Thus, the significance of the union in Christ is not the communication of divine energies, but becoming a “son” of God by transforming one’s hypostasis through a relationship identical with that of the Son. Christ is the “one” and the “many” in whom our hypostases are not merged or absorbed, but transfigured, or rather constituted in the relationship which Christ has with the Father. It is within this relationship that the human person becomes, or exists eternally as a unique and unrepeatable being. (“Divine Energies or Divine Personhood,” Modern Theology 19 [July 2003], p. 369)
Baptized into Christ we are made sons in the Son. This union with the risen Lord is the realization of immortality and eternal salvation. Thus sings the Apostle: “O death, where is thy victory? O death, where is thy sting?”