Here is one optimists reason for believing unity will prevail ... within the next hundred years ... nationhood as we know it will be obsolete; all states will recognize a single, global authority. A phrase briefly fashionable in the mid-20th century -- citizen of the world -- will have assumed real meaning by the end of the 21st. All countries are basically social arrangements, accommodations to changing circumstances. No matter how permanent and even sacred they may seem at any one time, in fact they are all artificial and temporary.