In his prayer for the disciples at the last super, Jesus prays this verse.
I will remain in the world no longer, but they are still in the world, and I am coming to you. Holy Father, protect them by the power of your name, the name you gave me, so that they may be one as we are one.
and later in verse 22 and 23
22 I have given them the glory that you gave me, that they may be one as we are one— 23 I in them and you in me—so that they may be brought to complete unity. Then the world will know that you sent me and have loved them even as you have loved me.
Perhaps I have made incorrect assumptions about this verse, but I have always thought that when he says "so that they may be one" he is not only referring to the disciples but the entire Church or all Christians. Also, when he says "as we are one" he means his participation as the second person of the trinity, with God the Father.
If this is correct, I have never understood, in what ways we as finite beings, can be 'one', in the same way, or a similar way, as the persons of the trinity are are 'one'? What is 'complete unity'?