To understand the ideas shaping the Trump administration, the political scientist Cas Mudde once told me, you have to understand populism, authoritarianism, and nativism, because Donald Trump “fires on all three cylinders.” I’ve previously explored the definitions of populism and authoritarianism. But what is nativism? How is it different from “nationalism” or “patriotism”—words that the alleged nativists themselves typically use to describe their ideology? Is Trump, the man who just ordered air strikes against a foreign leader for attacking people in a foreign country, really a nativist? And why, when it would seem to raise valid questions about the rights of natives versus non-natives, does nativism have such negative associations?