Christmas came along at just the right moment to destabilize that glorious story. Luke is impeccably conscious of the emperor and his vassals (that is where we get those sonorous phrases in the Christmas story about "Quirinius the governor of Syria"). But Luke believes, against all odds, that something more important is happening in Bethlehem than Rome, that a baby born of an unwed, unknown mother is of greater significance than Julius Caesar's adopted son. His angels announce that history is indeed taking a great and decisive turn toward peace on earth, but one that has nothing to do with the empire's peace. A king is coming into the world, the coin of whose realm will be sacrifice and gift, not coercion and taxation.
Only familiarity could cause us to miss one of the most extraordinary aspects of Luke's Christmas story: how matter-of-fact it is. "And it came to pass in those days, that there went out a decree from Caesar Augustus that all the world should be taxed"—these prosaic words signal Luke's intention to write as if, with Tacitus or Pliny, he is simply recounting the plain facts of history. The difference, of course, is that the Roman historians were recording events of universally agreed significance. Luke's virgin, shepherds, and stable seem marginal and fleeting, beneath notice to the status-conscious Roman elite. Luke's serene confidence that he is recounting "good tidings of great joy, which shall be to all people," seems about as probable as, well, an angelic choir above a Galilean hillside.
Yet we now read Tacitus and the rest for their antiquarian interest alone. They are mere history, dusty and distant, whereas Luke's utterly improbable cast of characters and fundamental convictions now rest at the foundation of our society's most cherished commitments and greatest flights of imagination. Against the highest possible odds, Luke's confidence in the lasting significance of his story has been vindicated.
Popes and Emperors
And it turns out, from our very long view, that the moment when Augustus Caesar's divine power seemed most secure was the moment when it began to recede. Three hundred years later nearly half the empire would be Christian, so that Constantine's embrace of the insurgent faith in 313, however sincere it may have been, was also canny political positioning.
There would still be emperors, and even a Holy Roman Empire, but the emperor would never again wield Caesar's absolute power. Instead, emperors increasingly had to contend with a troublesome figure, the new Roman "pontiff." That title for the high priest in Rome, which Caesar had taken for himself, now belonged to Rome's Christian bishop—as did the role of civic "paterfamilias," everyone's papa, the pope.
Popes and emperors would tussle for the next thousand years. A millennium after the first Christmas, an ally of the emperor Henry IV took Pope Gregory VI hostage as he celebrated Christmas mass in 1075. The pressure tactic failed, Henry was excommunicated, and two years later he made his famous pilgrimage in the January snow to the pope's fortress in Canossa, begging for an opportunity to repent.