And how do Americans celebrate this extraordinary success? By denying it. Every year Gallup asks whether crime has gone up or down since the previous year. Every year, rain or shine, the public insists, usually by overwhelming margins (63 percent to 21 percent in 2014), that crime has risen. “Most Americans Unaware of Big Crime Drop Since 1990s,” announced the Pew Research Center in 2013; only 10 percent of those surveyed knew that gun crimes had gone down since the 1990s. Criminologists say that many people get angry when told that crime is decreasing.

Perception is even more skewed where terrorism is concerned. “Terror-ism Worries Largely Unchanged,” ran another Pew headline, also in 2013. That year, 58 percent of the public was worried about another terrorist attack in the United States, a rate not all that much lower in October 2001, immediately after the 9/11 attacks, when 71 percent of the public was worried. A few months ago, perhaps influenced by ISIS’s atrocities, a large plurality of respondents told NBC News/Wall Street Journal pollsters that the country is less safe than it was before 9/11.

Reality, once again, tells us otherwise. State-sponsored international terrorism, writes the intelligence analyst Paul R. Pillar in Cato’s A Dangerous World?, “is today only a shadow of what it was in the 1970s and 1980s.” As for the risk posed by terrorism inside the United States, to characterize it as trivial would be very generous. Americans are about four times as likely to drown in their bathtub as they are to die in a terrorist attack. John Mueller of Ohio State University and Mark G. Stewart of Australia’s University of Newcastle estimate the odds of such deaths at one in 950,000 and one in 3.5 million, respectively.

Surely we can at least agree to worry about a nuclear Iran, or nuclear terrorism, or ISIS? All are indeed worrisome, but Mueller persuasively argues that none merits the alarm it begets. Since Nagasaki in 1945, the few countries that have obtained nuclear weapons—including dangerous rogue states like Mao’s China, the Iran of its day—have consistently found them militarily and diplomatically useless, except as ego boosters and perhaps as defensive weapons to forestall attack. The odds of terrorists’ obtaining and deploying nuclear weapons are much lower than most people appreciate, for a host of technical and political reasons. ISIS, meanwhile, is an unusually vicious and destabilizing actor in a region that is full of them, but its menace has been almost entirely local. (In this issue’s cover story, Graeme Wood examines this threat, and the appropriate response, in detail.)

Pinker, a psychologist at Harvard, mused in a recent speech about Americans’ odd refusal to appreciate their security. The bad news for Obama, if Pinker is correct, is that presidential palaver will have no effect, because people are hardwired to overreact to threats, real or perceived. In today’s world, where intricate social systems keep us safer than our forebears could ever have imagined, overreaction is maladaptive: it is often more disruptive and damaging than whatever provoked it. In the world we evolved for, however, humans needed to be hyperalert. Something rustling in the bush was more likely to be a predator or an enemy than a friend with glad tidings. Moreover, Pinker says, people are biased to overestimate the likelihood of the sorts of events that stand out in our memory, as violence and mayhem do, and as peace and quiet do not. Add alarmism’s usefulness to politicians and pressure groups, and you have a standing order for overreaction—always, not just now.