John Webster is commenting on Dietrich Bonhoeffer’s understanding of our relation to Scripture. It’s not as if we give scripture its ground through imbuing it with our exegetical prowess; no, it’s that our ground is given footing as we find ourselves related to God in Christ through Scripture’s story. This fits with the point that Webster is driving at, over-all, throughout his little book; that Scripture should be seen as an aspect of soteriology — sanctification in particular. And that Scripture is a part of God’s triune communicative act, ‘for us’, caught up in His self-Revelation itself. In other words, for Webster, as for Bonhoeffer (per Webster), Scripture shouldn’t be framed as a component of our epistemological foundation (wherein we put Scripture in its place, in effect), but Scripture is a mode of God’s gracious speech that acts upon us by the Spirit. And it is through this divine speech, that is grace, that we find ourselves — outside ourselves — in Christ, and thus in the Story of Scripture. This should have the effect of placing us under Scripture (which Luther would call ministerial) versus over Scripture (magisterial) — to simplify. Here’s the quote (a little introduction by Webster, and then a full quote of Bonhoeffer [also, notice the idea of vicariousness that Bonhoeffer appeals to as well]):
[M]ore than anything else, it is listening or attention which is most important to Bonhoeffer, precisely because the self is not grounded in its own disposing of itself in the world, but grounded in the Word of Christ. Reading the Bible, as Bonhoeffer puts it in Life Together, is a matter of finding ourselves extra nos in the biblical history:
We are uprooted from our own existence and are taken back to the holy history of God on earth. There God has dealt with us, with our needs and our sins, by means of the divine wrath and grace. What is important is not that God is a spectator and participant in our life today, but that we are attentive listeners and participants in God’s action in the sacred story, the story of Christ on earth. God is with us today only as long as we are there.
Our salvation is ‘from outside ourselves’ (extra nos). I find salvation, not in my own life story, but only in the story of Jesus Christ . . . What we call our life, our troubles, and our guilt is by no means the whole of reality; our life, our need, our guilt, and our deliverance are there in the Scriptures. – John Webster, Holy Scripture, 83 citing Dietrich Bonhoeffer, “Life Together,” 62.