Are you aware that Jesus Christ gave his own definition of the unity and oneness that exists between him and his Father, God? His explanation is so simple and so clear that it is impossible to misunderstand it without ignoring or rejecting it.
What did Jesus say about this?
John 17:11.
11 ¦ And now I am no more in the world, but these are in the world, and I come to thee. Holy Father, keep through thine own name those whom thou hast given me, that they may be one, as we [are].
That's it! See how simple that is? Jesus wants us to be one, just like he and his Father are one. There is no hint of a mystery here, unless it is the mystery that a man can walk so closely with God as to experience this kind of unity with him.
So what does this mean? In your mind, pick out the person who is your closest brother or sister in Christ. Now, describe how the two of you are, or are becoming, one.
Are you finished? If there is any unity between the two of you to describe, then you have succeeded in describing in some small measure the unity that exists between God and Christ.
In another passage in the same chapter, Jesus goes into a bit more detail about this unity between himself, his Father, and us.
John 17:20-23.
20 ¦ Neither pray I for these alone, but for them also which shall believe on me through their word;
21 That they all may be one; as thou, Father, [art] in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me.
22 And the glory which thou gavest me I have given them; that they may be one, even as we are one:
23 I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me.
Christ's desire, and God's, is that we be united in them. Christ is in us, and God is in Christ. Unity in the church apart from unity with God and Christ is a perversion of God's purpose. The reason God wants us to have this kind of unity in Christ is so that the world can believe that God sent Christ.
The beauty of this is that we're not left out. We're not sitting on the sidelines somewhere admiring the beauty of the unity enjoyed by God and Christ. We've been invited to share in this unity with them, and with each other.
I John 1:3-4.
3 That which we have seen and heard declare we unto you, that ye also may have fellowship with us: and truly our fellowship [is] with the Father, and with his Son Jesus Christ.
4 And these things write we unto you, that your joy may be full.