Jesus prays in today's Gospel reading for all of us who come to believe him. He prays that we may be one. What does it mean for us to be one? The answer forms the second part of Jesus's prayer. We are one when we come to share the unity that Jesus, the Son, enjoys with the Father.
What makes the Christian concept of God distinctive is not its belief that God is one as such. Other religions too believe that God is one. They are monotheistic faiths. The distinctiveness of the Christian concept of God lies rather in that it is Trinitarian. God is Father, Son and Holy Spirit. This complex unity within God has been revealed to us though the coming of the Son in the human person of Jesus and in the gift of the Spirit.
It may often be necessary to insist that we Christians are monotheists, especially if we have the opportunity to engage in a constructive dialogue with our Muslim brothers and sisters. But we should not dilute or ignore the fact that is it the threefold personhood of God that is at the very heart of our Christian understanding and experience of God.
So, when Jesus prays that we may be one as he and the Father are one, this means that we may come to share in the rich unity-in-diversity that is manifest in the Trinity. Genuine unity for us never means the belittlement or elimination of difference, be it between the men and women who make up the community of believers, or between human beings and the God they strive to know and love.
The unity-in-diversity of believers is manifest in our understanding of the Church. The image of the community of believers as the body of Christ is very important and apt here if we are to understand Jesus's prayer correctly. The body has many members, even though always one organic unity. This diversity is essential to the nature and functioning of the body.
The words of Jesus in the Gospel for today have rightly been taken as the motto for Christian ecumenism. Christians should recognise and find common bonds and overcome what divides them. Yet the rich diversity of expressions of Christian faith and culture is also part of what it means for Christ to be ever more greatly incarnated into our human world.
Moreover, the unity-in-diversity of the believer with God is manifest in the balance between coming to be one with God and remaining ever-distinct from God. At the end of our Gospel passage Jesus prays: 'I have made known to them thy name, and I will make it known, that the love with which thou has loved me may be in them and I in them.' Jesus discloses the unity of the Trinity to us as a communion of knowledge and love, as well as of being. Jesus is the one who is known by the Father and who knows the Father fully; Jesus is the one who is loved by the Father and who loves the Father fully.
So, the unity we have with God is one that is manifest in our own coming to know and love the Father. This is what we mean by union with God, by the beatific vision.
And yet here too the diversity is also important. We are meant to enter into a relationship with God, not become God. Very often we emphasise the idea of the sanctification, even the divinisation, of human beings, as they come to share in the life of God. Yet, the marvel here is not so much that God sanctifies, but that he sanctifies us. In other words, that God wants to have this relationship with us. And such a relationship can only occur if we are distinct from God.
God loves diversity, as is manifest in his creative will and action. There is a value and dignity in being a human creature made by God. There is a value and dignity in the diversity of human races and cultures as made by God, which share a unified human nature. There is also a value and dignity in the rich and varied creation itself in all its forms, which together make up the unified whole that is the world.