What really is Christianity? If all the religious packaging in which it is wrapped were removed, what would remain? These were Bonhoeffer’s questions, and they must be ours today–even more urgently! For in many quarters Christianity is being so narrowly identified with some of its parts, cultural associations, and past ambitions that like all militant religion, it represents a threat to the planetary future. We may no longer speak clearly of the essence of Christianity, as von Harnack and other nineteenth-century thinkers did; but perhaps we may still have a sufficiently shared sense of the kerygmatic core of this faith to be able, in the face of these misrepresentations of it, to say what Christianity is not.