Now the body of Christ,
as I often have said,
is the whole of humanity.
— St. Gregory of Nyssa
It is a truth of the Incarnation, in which Christ has united himself with all of humanity, that the body of Christ is the whole of humanity. For there is only one humanity in which we all share, and Jesus shares in it with us. That one humanity is thus united with God. It violates no logic. It is not a redefinition except inasmuch as the coming of Christ into the world changes everything. This concept was well defined in the early Church, as Gregory of Nyssa (c. 335-395) demonstrates. He was no theological hack, and orthodox Christian understanding today owes much to him.
We find the Incarnation in John 1: “In the beginning was the Word, and the Word was with God, and the Word was God ... The Word became flesh and made his dwelling among us. We have seen his glory, the glory of the one and only Son, who came from the Father, full of grace and truth” (John 1:1, 14). This and many other passages shows the intimate connection between Christ and all humankind. He did not become human in a different humanity but in the only one there is. We are all and united in it, and Christ shares in it with us.
So thoroughly united is all humankind with Christ, Paul can say that, just as Adam’s disobedience resulted in condemnation for all humankind, so also Christ’s righteous act resulted in justification and life for all people (Romans 5:18). And that, just as in Adam all die, so also in Christ all will be made alive (1 Corinthians 15:22).
Because all humankind is united with and in Christ, and Christ is united with and in all humankind, there can be no situation where only some are the body of Christ while others are not. For Christ would have to be disunited with that part of humanity which is not his body, and that would be the undoing of the Incarnation. And the undoing of the Incarnation would be the undoing of salvation not just for some but for everyone.
This Incarnational union and embodiment does not at all do away with divine judgment but is precisely the means of that judgment — and it happens through the Cross and Resurrection. This is how God sets everything right in the world, making all things new.
Inasmuch as in Christ all will be made alive in the end, then all humankind, eschatologically understood, is the body of Christ. And inasmuch as humankind is inextricably bound with creation, and Christ is inextricably bound with humankind, so Christ is inextricably bound with creation. All creation is in him, as Paul tells us in Colossians 1, and Christ is in all creation — Christ is all and in all. Just as all of humankind, eschatologically understood, is the body of Christ, so also, all of creation, eschatologically understood, is the body of Christ.
There is no place in creation where Christ is not present. Not one part, not one cell, not one atom. But Christ is in all of creation, every bit of it. This means that Christ is embodied in throughout all creation, so thoroughly united with all creation that all in heaven and on earth are brought to unity in Christ, headed up in Christ (see Ephesians 1:9-10).