Why does this matter? Because the U.S. government has finite resources. If you assume, as conservatives tend to, that the only significant terrorist threat America faces comes from people with names like Mohammed and Ibrahim, then that’s where you’ll devote your time and money. If, on the other hand, you recognize that environmental lunatics and right-wing militia types kill Americans for political reasons too, you’ll spread the money around.

We’ve already seen the consequences of a disproportionate focus on jihadist terrorism. After 9/11, the Bush administration so dramatically shifted homeland-security resources toward stopping al-Qaeda that it left FEMA hideously unprepared to deal with an attack from Mother Nature, in the form of Hurricane Katrina. The Obama administration is wise to avoid that kind of overly narrow focus today. Of course it’s important to stop the next Nidal Malik Hasan or Dzhokhar Tsarnaev. But it’s also important to stop the next Timothy McVeigh or Wade Michael Page. And by calling the threat “violent extremism” rather than “radical Islam,” Obama tells the bureaucracy to work on that too.

Obama, after all, faces two overlapping but distinct challenges. One is an ideology: the totalitarian, even genocidal, vision espoused by ISIS. The second is a tactic: terrorism, which is available to people of all ideological stripes and which grows more dangerous as technology empowers individuals or groups to kill far more people far more quickly than they could have in ages past.