Americans are special. Since the Puritans sailed into Massachusetts Bay in 1630, we have believed it. Even before we could get off the ship, Massachusetts' first governor, John Winthrop, explained it to us. We were to be a city on a hill, a light to the nations, the new Israel. Iconic politicians from John F. Kennedy to Ronald Reagan have invoked this famous biblical imagery to explain America's role in the world. This year's Republican presidential candidates can't stop talking about it.