I want to share with you a bit on Don Carson’s commentary on John’s Gospel, as relates to John17, the passage of the moment for a few of us. I hope this is not very very illegal… for those of you who read the bible :P this commentary is excellent do go out and get one. I’ve bolded the bits that struck me, and particularly “the unity is meant to be observable” building to the conclusion “It is hard to imagine a more compelling evangelistic appeal”..
This extension to those who will believe through the witness of the original disciples assumes that their witness will in some measure prove effective. What Jesus prays for these believers-to-be is that 'all of them may be one' (v21) – a petition whose significance is further unpacked is the remaining clauses of the verse. This is not simply a 'unity of love'. It is a unity predicated on adherence to the revelation the Father mediated to the first disciples through his Son, the revelation they accepted (vv6-8) and then passed on ('those who will believe in me through their message' v20). It is analogous to the oneness Jesus enjoys with his father, here fleshed out in the words 'just as you are in me and I am in you'. The Father is actually in the Son, so much so that we can be told that it is the Father who is performing the Son's works (14:10); yet the Son is in the Father, not only in dependence upon and obedience to him, but his agent in creation (1:2-3) and his wholly concurring Son in the redemption and preservation of those the father had given him (e.g. 6:37-40, 17:16, 19) The Father and the Son are distinguishable (the pre-incarnate Word is 'with' God, 1:1; the Son prays to his Father; the Father commissions and sends, while the Son obeys), yet they are one.
Similarly, the believers, still distinct, are to be one in purpose, in love, in action undertaken with and for one another, in joint submission to the revelation received. More: Jesus prays to his Father that these disciples may 'also be in us', probably alluding to the 'union' language of the vine metaphor (ch15). They are 'in' the Father and his Son, so identified with God and dependent upon him for life and fruitfulness, that they themselves become the locus of the Father's life and work 'in them' (14:12, 15:7). All of this is to the end 'that the world may believe that you have sent me'. As the display of genuine love amongst the believers attests that they are Jesus' disciples (13:34-5), so this display of unity is so compelling, so unworldly, that their witness as to who Jesus is becomes explainable only if Jesus truly is the revealer whom the Father has sent.
Although the unity envisaged in this chapter is not institutional, this purpose clause at the end of v21 shows beyond possibility of doubt that the unity is meant to be observable. It is not achieved by hunting enthusiastically for the lowest common theological denominator, but by common adherence to the apostolic gospel, by love that is joyfully self-sacrificing, by undaunted commitment to the shared goals of the mission with which Jesus' followers have been charged, by self-conscious dependence on God himself for life and fruitfulness. It is a unity necessarily present, at least in nuce, amongst genuine believers; it is a unity that must be brought to perfection (v23)
The nature of the unity is further unpacked. The 'glory' (1:4) that the Father gave the Son he has transmitted to his followers. Exactly what is meant by these clauses is much disputed. Some tie this glory to that for which Jesus prays in 17:1,5, but this makes v22 necessarily anachronistic. On the whole, it seems best not to take 'them' as a reference to the original disciple alone, but as a reference to all disciples, including those who will (later) believe through the witness of Jesus' first followers. If so, Jesus has given his 'glory' to them in the sense that he has brought to completion his revelatory task (if as in v4-5 and repeatedly throughout the chapter, he may be permitted to speak proleptically and thus include his climatic cross-work). 'Glory' commonly refers to the manifestation of God's character or person in a revelatory context; Jesus has mediated the glory of God, personally to his first followers and through them to those who believe on account of their message. And he has done all of this 'that they may be one as we are one'.
Some measure of unity is the disciples is assumed, but Jesus prays that they may be 'brought to complete unity', sharing richly in both the unity of purpose and the wealth of love that tie the Father and the Son together. The purpose, as in v21, is 'to let the world know that you sent me', to which is now added the further goal, 'that you ... have loved them even as you have loved me'. The thought is breathtakingly extravagant. The unity of the disciples, as it approaches the perfection that is its goal (tetelimenoi – the use of this verb in 4:34, 5:36, 17:4) serves not only to convince many in the world that Christ is indeed the supreme locus of divine revelation as Christians claim ('that you have sent me'), but that Christians themselves have been caught up into the love of the Father for the Son, secure and content and fulfilled because loved by the Almighty himself (Eph3:17-19), with the same love he reserves for his Son. It is hard to imagine a more compelling evangelistic appeal.
http://books.google.co.uk/books?id=zBRuo3LHyS4C - includes this quote in the pages available online
Other Don Carson Bits: