The Parkland shooting earlier this year seemed at last to ignite a public movement in response to these terrible crimes. Yet even the cumulative impact of slaughter after slaughter has not softened the harsh divide of the American gun impasse. Back in 2012, Nate Silver observed: “Whether someone owns a gun is a more powerful predictor of a person’s political party than her gender, whether she identifies as gay or lesbian, whether she is Hispanic, whether she lives in the South, or a number of other demographic characteristics.”

More than 70 percent of Trump voters in 2016 described guns as “very important” to their vote, versus only 40 percent who described abortion as “very important” to their vote and only 25 percent who felt that way about gay rights. With the slow fading of battles over same-sex marriage and abortion, and the rapid collapse of other aspects of conservative ideology, guns may now rank as the single most important political dividing line in 21st century America.

Only 30 percent of Americans own guns. Thus far, that minority has sufficed to block substantial federal action on guns. But a one-third minority—and especially a nonurban one-third minority—may no longer suffice to shape American culture.

The outrage after Parkland looked less like a political movement, and more like the great waves of moral reform that have at intervals since the 1840s challenged the existing political order in the name of higher ethical ideals. The most important success of Mothers Against Drunk Driving, for example, was not to change laws (although they changed some), but to change hearts: to persuade Americans that drunk driving was not funny, not charming, and not acceptable.

American gun culture in the 2010s is as blithely irresponsible as American alcohol culture in the 1960s.

According to a Pew survey, only about one-quarter of gun owners think it essential to alert visitors with children that guns may be present in the home. (Twice as many non-gun-owners think so.) Only 66 percent of gun owners think it essential to keep guns locked up when not in use. (Ninety percent of non-gun-owners think so.) Only 45 percent of them actually do it.

This carelessness and disregard is taking lives and breaking families. The first step toward correcting a social wrong is opening people’s eyes to see that wrong. America has now tallied still more victims and broken the hearts of still more mourners. It’s a horrible price to pay for a moral reckoning and awakening—but the history of the nation promises that while the awakening may often come tragically slow, it does come in time, with all the power of justice delayed but not denied.

* This article originally stated that the last school shooting in Canada was in 2007. We regret the error.