The cross is, in the first instance, God's attack on human sin. As an attack, it reveals that the real seat of sin is not in the flesh but in our spiritual aspirations, in our "theology of glory". Thus, the theology of the cross is an offensive theology. Unlike other theologies it attacks what we usually consider the best in our religion.
The most common overarching story we tell about ourselves is what we will call the glory story: We came from glory and are bound for glory. Of course, in between we seem somehow to have gotten derailed, but that is only a temporary inconvenience to be fixed by proper religious effort. What we need is to get back on "the glory road". The story is told in countless variations. Usually the subject of the story is "the soul." The basic scheme is what Paul Ricoeur has called "the myth of the exiled soul." The soul is exiled from its home, and its true destiny is to return.
Indeed, so seductive has the exiled soul myth been throughout history that the biblical story itself has been taken into captivity by it. The biblical story of the fall has tended to become a variation on the theme of the exiled soul. Adam, originally pure in soul, either by nature or by the added gift of grace, was tempted by baser lusts and "fell", losing grace and drawing all his progeny with him into a "mass of perdition." Reparation must be made, grace restored, and purging carried out so that a return to glory is possible. The cross, of course, can be quite neatly assimilated into the story as the reparation that makes the return possible. And there we have a tightly woven theology of glory!
One of the difficulties in the attempt to set the theology of the cross apart from the theology of glory is that the differences between the two are often very subtle. The theology of the cross arises out of the realization that it is simply disastrous to dissolve the cross in the story of glory. Jesus was crucified "outside the camp," not in the temple. The cross insists on being its own story. It does not allow us to stand by and watch. It does not ask us to probe endlessly for a meaning behind or above everything that would finally awaken, enlighten, and attract the exiled, slumbering soul. The cross draws us into itself so that we become participants in the story. Just as Jesus was crucified, so we also are crucified with him. The cross makes us part of its story. The cross becomes our story. That is what it means to say, as Luther did, "The cross alone is our theology."
-- Gerhard Forde
selected from his book:
On Being a Theologian of the Cross, (Reflections on Luther's Heidelberg Disputation, 1518)