We take for granted today how remarkable the modern nation is. Countries like the United States, the United Kingdom, France and Russia contain multitudes of different types of individuals, the vast majority of whom are relatively unaffected by foreign policy. Hans Morgenthau pointed out that nationalism drives these disparate individuals to experience the power and policies of their nations as their own, and that aggressive nationalism is often a result of economic or political stress. This is the great paradox of nationalism. It supplanted tribalism, faith and monarchy as the organizing principle of the international order in the 19th and 20th centuries, and it is the glue that binds diverse groups of individuals together into states. But it also means defining who isn’t a part of the nation, which can unbind both society and broader international institutions. (...) Today, nationalism in certain urban areas comes from a different source than in suburban and rural areas. The urban-rural split is not a novel discovery, but it has become more pronounced as a result of resurging nationalism. For example, when people in the U.K. voted on whether to remain in the European Union, Wales and England voted to leave. Scotland, Northern Ireland and the City of London voted to remain. The result of the referendum in London is the most striking. Scotland and Northern Ireland have been independent at various points in history, but London has been the capital of what is today England for almost a millennium. Of all Londoners, 60 percent voted to remain in the EU, but the majority of English voters wanted to leave. Some suggested (maybe jokingly) that, just as Scotland and Northern Ireland have done, London should explore whether it can remain within the EU and leave the rest of England behind. (...)