CHRISTMAS is a dangerous time, for it threatens social instability, political disorder, even revolution. At the culmination of the story, kings kneel before a helpless baby — the powerful pay tribute to the seemingly powerless.

To understand the destabilising potency of Christmas, one has only to recall Andreas Karlstadt, an iconoclast in the literal sense, shouting the words of institution in German, not Latin, and offering both the communion cup and the wafer to the trembling hands and lips of the unconfessed laity in Wittenberg on December 25 1521, in the first years of the Lutheran Reformation.

Martin Luther’s 1522 sermon on the Epiphany can be read as part of his larger project to shore up the political order threatened by the radicalism of Karlstadt and others.