President Trump’s executive order targeting anti-Semitic and anti-Israel speech on campuses might be framed as a narrow legal matter, but it has touched on a defining issue of our time: Who belongs, and who decides?

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What Is National Identity?

The concept, scarcely 200 years old, holds that humanity is divided among fixed communities, each defined by a common language, ethnicity and homeland. Those communities are nations; membership is one’s national identity. The core tenet of nationalism so pervades today’s world that it feels almost self-evident: Any nation of people should have a country, and any country should consist of a nation.

The concept of an overarching identity tied to one’s country was invented not by ancient poets or warriors but by 19th-century European governments. As monarchies teetered and the church declined, governments saw engineering common languages and ethnic heritages as a way to justify their rule over polyglot empires, as well as an opportunity to marshal their populations for collective pursuits like industry or war.

“Nations as a natural, God-given way of classifying men, as an inherent though long-delayed political destiny, are a myth,” the British-Czech political theorist Ernest Gellner wrote.

But this way of thinking reshaped 19th-century Europe, leading to the creation of modern Italy and Germany. It later spread to the rest of the world, inspiring independence and liberation movements on the basis that all people belong to national groups awaiting their nation.

National identity’s rise, however, also turned minorities and migrants into second-class citizens — or even into perceived threats within. It turned racial purity into a matter of ethnic, and therefore national, survival. It defined nations as irrevocably divided from one another by race and heritage.