In his statement after the terrorist attack in Orlando, Donald Trump called on U.S. President Obama to resign and on Hillary Clinton to quit the presidential campaign. The reason: They “refused to even say the words ‘Radical Islam.’” (Clinton later uttered the phrase, so I guess she’s allowed to stay in the race.)

As per usual, Trump is saying something other Republicans have said before. He’s just saying it more crudely. Last November, Jeb Bush said that, “[F]or the life of me, I have a hard time understanding why people get twisted up in knots to avoid saying that this is radical Islamic terrorism.” This January, Ted Cruz declared that, “You cannot fight and win a war on radical Islamic terrorism if you’re unwilling to utter the words ‘radical Islamic terrorism.’”

Bush, Cruz and Trump love the term “radical Islam” because it supposedly provides “moral clarity” to America’s anti-terror war. But there’s a problem. A term can’t provide “moral clarity” if you don’t know what it means.

“Radical” has two meanings. The first is “fundamental.” “Radical” comes from the Latin “radix,” which means “root.” When Omar Mateen murdered 49 LGBT night clubbers, was he reflecting the fundamentals of Islam? Many Republicans think so. A December 2015 poll by the Pew Research Center found that 68 percent of Republicans, compared to only 30 percent of Democrats, believe that Islam is more likely than other religions to promote violence among its adherents.

If “radical” means “fundamental” or “essential,” then “radical Islam” is redundant. Saying America is at war with “radical Islam” is pretty much the same as saying that America is at war with Islam. That’s certainly what ISIS believes. And it’s not far from what Trump believes either. After all, the presumptive Republican nominee didn’t respond to the San Bernardino shooting by calling for the United States to ban “radical Muslims” from entering from the United States. If he had, he would have had to explain which Muslims are “radical” and which are not. Instead, he called for banning all Muslims. The implication is that all Muslims are “radical,” at least until proven otherwise.

But if “radical” means “fundamental,” it has also come to mean “extreme.” I suspect that’s why Republicans find the term so useful. Because it appeals both to voters who believe that ISIS represents authentic Islam and to those who believe that ISIS represents a drastic, “extreme” form of Islam.

Saying that America is at war with “extreme” Islam is less dangerous than saying America is at war with “fundamental” Islam, since it doesn’t put America in conflict with everyone who believes they practice the true faith. Conceptually, however, the term still offers little clarity. “Extreme” has no moral or ideological content. It just means unusual. Mother Theresa’s unusual devotion to Calcutta’s poor made her an “extreme Christian.” Ultra-Orthodox Jews' unusual devotion to keeping the mitzvot makes them “extreme Jews.” Saying that ISIS’s brand of Islam is “extreme” doesn’t explain why we should oppose it, let alone go to war against it.

The problem isn’t that ISIS is “extreme.” It’s that ISIS is totalitarian. Like North Korea, like Khmer Rouge Cambodia, like Nazi Germany and like Stalin’s Soviet Union, it seeks total control of how the people under its reign act. Authoritarian regimes seek to control their subjects’ political behavior. Totalitarian regimes also seek to control their social, cultural and religious behavior. “If totalitarianism takes its own claim seriously,” wrote Hannah Arendt, “it must come to the point where it has ‘to finish once and for all with the neutrality of chess,’ that is, with the autonomous existence of any activity whatsoever.” In the Islamic State, you can be punished for possessing cigarettes, for not wearing socks, for not growing a beard and for not correctly answering theological questions at a checkpoint.

The United States has at times coexisted with totalitarian regimes. It fought alongside Stalin’s Soviet Union in World War II. But because ISIS sought to overthrow an American-backed regime in an oil-rich country, the United States responded by going to war. In 2014, the Obama administration launched air strikes against the group both because its totalitarian ideology led it to attempt genocide against the Yazidi religious minority and because it began taking over large chunks of Iraq. Since then, ISIS has escalated its efforts to murder civilians in the United States and in those other countries that have joined the U.S. in its war.

Obama and Clinton say the United States is at war with ISIS (as well as its forerunner, Al-Qaida). That makes sense because Americans know what ISIS is. It also makes sense to define ISIS as a “totalitarian” Islamic organization, which uses terrorism to achieve its goals. It makes sense because since the middle of the twentieth century, political theorists have developed an understanding of what totalitarianism is.

“Radical Islam,” by contrast, can’t be coherently defined. It means either that Islam itself is the problem or it means that an unusual version of Islam is the problem — without ever defining what makes that version of Islam so bad. The phrase sounds menacing but is intellectually worthless. Much like the man who now puts it at the center of his presidential campaign.