Suppose you find yourself, in the late afternoon, in one of the English cathedral towns—Durham, say, or York, or Salisbury, or Wells, or Norwich—or in one of the great university cities, like Oxford or Cambridge. The shadows are thickening, and you are mysteriously drawn to the enormous, ancient stone structure at the center of the city. You walk inside, and find that a service is just beginning. Through the stained glass, the violet light outside is turning to black. Inside, candles are lit; the flickering flames dance and rest, dance and rest. A precentor chants, “O Lord, open thou our lips.” A choir breaks into song: “And our mouth shall shew forth thy praise.” The precentor continues, “O God, make speed to save us.” And the choir replies, musically, “O Lord, make haste to help us.