This is how Rob Bell answered this question:
I would say that history is headed somewhere. The thousands of little ways in which you are tempted to believe that hope might actually be a legitimate response to the insanity of the world actually can be trusted. And the Christian story is that a tomb is empty, and a movement has actually begun that has been present in a sense all along in creation. And all those times when your cynicism was at odds with an impulse within you that said that this little thing might be about something bigger—those tiny little slivers may in fact be connected to something really, really big.
Is Rob Bell’s “gospel” really a gospel in all its New Testament sense? What is missing? Or, what is Rob Bell really saying, because I surely don’t know what he is talking about; I think he’s talking about something big related to history that’s going somewhere, but I cannot tell by his statement what that big thing actually is nor where it is going.
Check out also Greg Gilbert‘s response to Bell’s statement.