After saying "shame on you" to Episcopalians who do not read Karl Barth, Walter Brueggemann sums up the work of this pre-eminent Protestant theologian as follows:
Karl Barth's huge insight -- out of which he wrote two billion pages of fine print -- is that you have to reason from what is real to what is possible.
As Brueggemann goes on to say, the modern world operates under the assumption that the possible dictates what is real, which destroys any chance of newness in the world.
I've only watched the first 10 minutes, but I have no doubt that watching this video will be time well spent for you and me.
Walter Brueggemann Lecture "Preaching the Old Testment" from School of Theology on Vimeo.