Gun enthusiasts frequently argue that only armed ordinary citizens could stop mass murderers. “Why didn’t the teacher have a gun?” they ask. No one’s seemed to offer a cogent response to that argument, apart from pointing out the difficulty of shooting only the assailant in a room full of panicking people. That’s a good response, but it’s not quite enough. Here’s a better one.

In 1651 the philosopher Thomas Hobbes pointed out that in a civilized society, the state has a monopoly on violence. In other words, the state secures the peace by way of a professional police force. It’s the job of the police to keep disputes from escalating into violence, and to ensure that they are resolved by law rather than by fists or bullets. That way, citizens don’t need to carry personal arms, nor do they need to be constantly on alert worrying about those who might. Steven Pinker sums it up well in his recent book The Better Angels of Their Nature: by restraining and penalizing aggressors, the State is “defusing general anxieties about preemptive attack and obviating everyone’s need to maintain a hair trigger for retaliation to prove their resolve” (p. 35). A well-regulated state maintains security so that people can go about their business in a peaceful and predictable world.