Still don't have the time to write properly on a Christian approach to cosmology. Never mind I'll jot down some thoughts as they occur.
For now, let me just jot down three thoughts on the multiverse, two quotes from Barth and then a suggestion about how to pursue Christian cosmology.
1) The Bible teaches a division of creation into invisible and visible - the heaven and the earth. This is not the same as the observable universe versus the non-observable multiverse. For the bible the unseen realm is intimately linked to the seen. Heaven is the counterpart to earth in a way analagous to the unseen Father's correspondence to His visible Image, Jesus.
2) The seen and unseen realms are reconciled to one another in the decisive, once-for-all event of the crucifixion. (Col 1:20)
3) There simply is no room in a Christian cosmology for multiple incarnations or multiple atonements. And this is really the downfall of the multiverse - its relation to Christ. Christ does not bridge multiple universes in multiple incarnation, He bridges heaven and earth in His singular incarnation.
Two Barth Quotes from Dogmatics in Outline
“‘Heaven and earth’ describe an arena prepared for a quite definite event, in the centre of which, from our standpoint of course, stands man.” (p60)
“…heaven and earth are related like God and man in the covenant, so that even the existence of creation is a single, mighty signum, a sign of the will of God. The meeting and togetherness of above and below, of the conceivable and the inconceivable, of the infinite and the limited – we are speaking of creation. All that is the world. But since within this world there really exist an above and a below confronting one another, since in every breath we take, in every one of our thoughts, in every great and petty experience of our human lives heaven and earth are side by side, greeting each other, attracting and repelling each other and yet belonging to one another, we are, in our existence, of which God is the Creator, a sign and indication, a promise of what ought to happen in creation and to creation – the meeting, the togetherness, the fellowship and, in Jesus Christ, the oneness of Creator and creature.” (p64)
How to proceed in Christian cosmology
Beginning from 'the Cosmic Fine-Tuner' would be like beginning with heaven alone. Beginning from the standpoint of the anthropic principle would be like beginning with earth alone. The Christian can refuse both option. We begin with the heavens and the earth - the theatre of God's Glory. Of course God's Glory is His Son, dying to save. The cross is the crux of creation (Col 1:20). When we begin with this in mind we are able to relate the unseen and seen coherently.
The Christian knows that not only is there a Word (Logos) to make sense of the world - not only an explanation beyond. That Word became flesh, taking our world to Himself. Therefore the Word from beyond has become a Word in our midst. The Christian can simultaneously be in touch with this world and with its Explanation - they are one in Christ.
While we ought not to approach Christ 'according to the flesh' (2 Cor 5:16), still according to the Spirit there is a way of examining this earthed Logos. Now 'according to the Spirit' means 'according to the Scriptures' and therefore this will be a thoroughly theological enquiry. And yet it will not for that reason be a groundless, ethereal investigation. This world in its this-world-ness has been taken up into the life of God and proven to be, beyond any question, a realm fit for God (Col 2:9).
Now that we have seen the creative Word in the world and now that we have seen Him - the visible Image - reconcile the world to the invisible Father in the creative Spirit, we have seen a triune dynamic that is inherent to all creation. Interpenetration of spirit and flesh, then and now, unseen and seen is at the heart of reality. This will lead us to expect similar perichoretic dynamics in the created order. As we move on from what the bible strictly says about creation, we will wear these bible-glasses to investigate creation. This conceptual framework will help us to understand the inter-related-ness of space and time, of waves and particles etc etc.
I'll have to leave it there.