We live, let’s imagine, in a city where children are dying of a ravaging infection. The good news is that its cause is well understood and its cure, an antibiotic, easily at hand. The bad news is that our city council has been taken over by a faith-healing cult that will go to any lengths to keep the antibiotic from the kids. Some citizens would doubtless point out meekly that faith healing has an ancient history in our city, and we must regard the faith healers with respect—to do otherwise would show a lack of respect for their freedom to faith-heal. (The faith healers’ proposition is that if there were a faith healer praying in every kindergarten the kids wouldn’t get infections in the first place.) A few Tartuffes would see the children writhe and heave in pain and then wring their hands in self-congratulatory piety and wonder why a good God would send such a terrible affliction on the innocent—surely he must have a plan! Most of us—every sane person in the city, actually—would tell the faith healers to go to hell, put off worrying about the Problem of Evil till Friday or Saturday or Sunday, and do everything we could to get as much penicillin to the kids as quickly we could.

We do live in such a city. Five thousand seven hundred and forty children and teens died from gunfire in the United States, just in 2008 and 2009. Twenty more, including Olivia Engel, who was seven, and Jesse Lewis, who was six, were killed just last week. Some reports say their bodies weren’t shown to their grief-stricken parents to identify them; just their pictures. The overwhelming majority of those children would have been saved with effective gun control. We know that this is so, because, in societies that have effective gun control, children rarely, rarely, rarely die of gunshots. Let’s worry tomorrow about the problem of Evil. Let’s worry more about making sure that when the Problem of Evil appears in a first-grade classroom, it is armed with a penknife.

There are complex, hand-wringing-worthy problems in our social life: deficits and debts and climate change. Gun violence, and the work of eliminating gun massacres in schools and movie houses and the like, is not one of them. Gun control works on gun violence as surely as antibiotics do on bacterial infections. In Scotland, after Dunblane, in Australia, after Tasmania, in Canada, after the Montreal massacre—in each case the necessary laws were passed to make gun-owning hard, and in each case… well, you will note the absence of massacre-condolence speeches made by the Prime Ministers of Canada and Australia, in comparison with our own President.

The laws differ from place to place. In some jurisdictions, like Scotland, it is essentially impossible to own a gun; in others, like Canada, it is merely very, very difficult. The precise legislation that makes gun-owning hard in a certain sense doesn’t really matter—and that should give hope to all of those who feel that, with several hundred million guns in private hands, there’s no point in trying to make America a gun-sane country.

As I wrote last January, the central insight of the modern study of criminal violence is that all crime—even the horrific violent crimes of assault and rape—is at some level opportunistic. Building a low annoying wall against them is almost as effective as building a high impenetrable one. This is the key concept of Franklin Zimring’s amazing work on crime in New York; everyone said that, given the social pressures, the slum pathologies, the profits to be made in drug dealing, the ascending levels of despair, that there was no hope of changing the ever-growing cycle of violence. The right wing insisted that this generation of predators would give way to a new generation of super-predators.

What the New York Police Department found out, through empirical experience and better organization, was that making crime even a little bit harder made it much, much rarer. This is undeniably true of property crime, and common sense and evidence tells you that this is also true even of crimes committed by crazy people (to use the plain English the subject deserves). Those who hold themselves together enough to be capable of killing anyone are subject to the same rules of opportunity as sane people. Even madmen need opportunities to display their madness, and behave in different ways depending on the possibilities at hand. Demand an extraordinary degree of determination and organization from someone intent on committing a violent act, and the odds that the violent act will take place are radically reduced, in many cases to zero.

Look at the Harvard social scientist David Hemenway’s work on gun violence to see how simple it is; the phrase “more guns = more homicide” tolls through it like a grim bell. The more guns there are in a country, the more gun murders and massacres of children there will be. Even within this gun-crazy country, states with strong gun laws have fewer gun murders (and suicides and accidental killings) than states without them. (Hemenway is also the scientist who has shown that the inflated figure of guns used in self-defense every year, running even to a million or two million, is a pure fantasy, even though it’s still cited by pro-gun enthusiasts. Those hundreds of thousands intruders shot by gun owners left no records in emergency wards or morgues; indeed, left no evidentiary trace behind. This is because they did not exist.) Hemenway has discovered, as he explained in this interview with Harvard Magazine, that what is usually presented as a case of self-defense with guns is, in the real world, almost invariably a story about an escalating quarrel. “How often might you appropriately use a gun in self-defense?” Hemenway asks rhetorically. “Answer: zero to once in a lifetime. How about inappropriately—because you were tired, afraid, or drunk in a confrontational situation? There are lots and lots of chances.”

So don’t listen to those who, seeing twenty dead six- and seven-year-olds in ten minutes, their bodies riddled with bullets designed to rip apart bone and organ, say that this is impossibly hard, or even particularly complex, problem. It’s a very easy one. Summoning the political will to make it happen may be hard. But there’s no doubt or ambiguity about what needs to be done, nor that, if it is done, it will work. One would have to believe that Americans are somehow uniquely evil or depraved to think that the same forces that work on the rest of the planet won’t work here. It’s always hard to summon up political will for change, no matter how beneficial the change may obviously be. Summoning the political will to make automobiles safe was difficult; so was summoning the political will to limit and then effectively ban cigarettes from public places. At some point, we will become a gun-safe, and then a gun-sane, and finally a gun-free society. It’s closer than you think. (I’m grateful to my colleague Jeffrey Toobin for showing so well that the idea that the Second Amendment assures individual possession of guns, so far from being deeply rooted in American law, is in truth a new and bizarre reading, one that would have shocked even Warren Burger.)