I’VE SAID THIS BEFORE, but it bears repeating. You probably know that neurologists have a term, proprioception, to describe our sense of ourselves and our body, its position and movement in space. What they haven’t yet named, so far as I know, is the cultural equivalent to proprioception: our sense of the world, of history, of our place in it and our ability to move and act, within and on it. Yet such an equivalent does exist: we believe our bodies to be whole and immortal, the world to be solid beneath our feet, we know our family loves us, as does God, and we assume that our nation (race, tribe, clan, call it what you will) is where we belong — to it we pledge allegiance. Until, that is, we don’t. Locke wasn’t off-base when he named solidity as the first of his simple ideas, the corner or keystone for all of the rest. He had less to say about those moments when the earth moves, a family splits, gods die, or our nation declares war on itself. One day...