There may indeed be an economic cost to Brexit, but politics isn't reducible to a stock index  something that Americans, having once made their own tumultuous exit from an offshore power, should reflexively understand. "You are not to inquire how your trade may be increased, nor how you are to become a great and powerful people, but how your liberties can be secured," Patrick Henry declared during a 1788 debate over ratifying the Constitution, "for liberty ought to be the direct end of your Government."