While death is a central topic from Kierkegaard's earliest journals to the last writings leading up to his 'martyrdom,' he treats death as essentially mysterious. In the Concluding Unscientific Postscript, Johannes Climacus insists that he has not understood death, while the discourse "At a Graveside" speaks of death as "undefinable" and a "riddle." Kierkegaard is also particularly averse to discussing the nature of the afterlife, leading some to claim he views the afterlife merely as a heuristic device for teaching the living to live well. However, Kierkegaard rejects neither the Christian doctrine of resurrection nor the notion of posthumous survival more broadly; rather, the essential moral meaning of death for the living has the interesting effect of making many ways of talking about death morally illegitimate