Emergent's Big Problem: Bonhoeffer predicted it.

"In 'Act and Being,' he [Bonhoeffer] used philosophical language to show that theology is not merely another branch of philosophy, but something else entirely.  For him philosophy was man's search for truth apart from God.  It was a type of Barth's "religion," in which man himself tried to reach heaven or truth or God.  But theology begins and ends with faith in Christ, who reveals himself to man, apart from such revelation, there could be no such thing as truth.  Thus the philosopher – and the theologian  who operates on philosopher's assumption – chases his own tail and gazes at his own navel.   He cannot break out of that cycle, but God, via revelation can break in." - p. 89 "Bonhoeffer" by Eric Metaxas.

This quote by Eric Metaxas about Bonhoeffer's view of philosophy and theology really captures the essence of what I've seen as one of, what was at one time,  the big problems in the Emergent Church Movement.  In taking on Philosophy's assumption that either there is no such thing as Truth or that Truth is unknowable by those trying to discern it, Emergent theology is doomed to "chasing it's own tail" and does not end in being able to arrive at knowledge about God.  As Bonhoeffer astutely observed, theology cannot be built on the assumptions of philosopher because theology does not start with man's search for truth but rather it "begins and ends with faith in Christ, who reveals himself to man..."     

If those in Emergent had read Bonhoeffer and Barth, maybe they wouldn't have led so many people down the path of Harnack and Schleiermacher.