This week, in an editorial titled "Don't Blame Mental Illness for Gun Violence," The New York Times noted that "less than 5 percent of gun homicides between 2001 and 2010 were committed by people with diagnoses of mental illness." The week before last, in a front-page editorial titled "End the Gun Epidemic in America," the Times urged Congress to ban "the slightly modified combat rifles used in California," a.k.a. "assault weapons" (although the rifles used in the San Bernardino massacre did not qualify for that label under California law). FBI data indicate that rifles in general, which include many guns that are not considered "assault weapons," were used in about 2 percent of homicides (and 3 percent of gun homicides) last year.

Why does the Times understand percentages when it comes to people with psychiatric diagnoses but not when it comes to people with guns? Probably because fear and loathing of firearms prevent its editorialists from thinking straight. But in light of these numbers, it seems quite unlikely that a ban on so-called assault weapons—even if it somehow eliminated the millions of "assault weapons" already in circulation, and even if murderers did not simply switch to other, equally lethal guns—would have a noticeable impact on gun violence, let alone that it would "end the gun epidemic in America."

Undaunted by that reality, Rep. David Cicilline (D-R.I.), joined by 123 cosponsors, this week announced the Assault Weapons Ban of 2015, which would "prohibit the sale, transfer, production, and importation of…semi-automatic rifles and handguns with a military-style feature that can accept a detachable magazine." Cicilline did not explain what he means by "a military-style feature," and so far I have had no luck locating the actual text of his bill. But assuming it resembles the "assault weapon" ban that Sen. Dianne Feinstein (D-Calif.) proposed in 2013, the prohibited features are things like pistol grips, barrel shrouds, threaded barrels, and folding stocks.

It's a mystery why Cicilline thinks such features make firearms especially lethal, let alone uniquely suited to mass murder. But that is what he claims to think. "The sole purpose of their existence," he told reporters on Wednesday, is "to kill as many people as quickly as possible." Rep. Janice Hahn (D-Calif.) agreed. "The assault weapons we're talking about today are not just any guns," she said. "They're not for hunting. They're not for target practice. These are weapons of war, designed to inflict the maximum amount of death and injury." Steny Hoyer (D-Md.), the Democratic whip, chimed in, averring that "assault weapons" are not appropriate for people who "want to protect themselves in their homes" either.

If the guns that Cicilline, Hahn, and Stoyer want to ban have no legitimate uses, how do they account for their popularity with law-abiding Americans? The Hill notes that "8 million to 9 million assault weapons…are already in circulation." The percentage of those guns used to kill people is minuscule. Evidently the rest are used for things like hunting, target practice, and self-defense—the very purposes for which Cicilline et al. deem them unsuited. Is it possible they know less about "assault weapons" than they think they do?

Bonus: Eugene Volokh lists four reasons why Second Amendment fans are as alarmed by "assault weapon" bans as Cicilline is by folding stocks.