Andreas Wimmer in Aeon:
hy do some countries fall apart, often along their ethnic fault lines, while others have held together over decades and centuries, despite governing a diverse population as well? Why is it, in other words, that nation-building succeeded in some places while it failed in others? The current tragedy in Syria illustrates the possibly murderous consequences of failed nation-building. Outside of the media spotlight, South Sudan and the Central African Republic went through similar experiences in recent years. In some rich and democratic countries in western Europe, such as Spain, Belgium and the United Kingdom, longstanding secessionist movements have regained momentum. Within our lifetimes, they might well succeed in breaking apart these states. On the other hand, there is no secessionist movement among the Cantonese speakers of southern China or among the Tamils of India. And why has no serious politician ever questioned national unity in such diverse countries as Switzerland or Burkina Faso?
Before answering these questions, it is necessary to define nation-building more precisely. It goes beyond the mere existence of an independent country with a flag, an anthem and an army. Some old countries (such as Belgium) haven’t come together as a nation, while other more recently founded states (such as India) have done so. There are two sides to the nation-building coin: the extension of political alliances across the terrain of a country, and the identification with and loyalty to the institutions of the state, independent of who currently governs. The former is the political-integration aspect, the latter the political-identity aspect of nation-building. To foster both, political ties between citizens and the state should reach across ethnic divides.
More here.