On July 22, 2011, a 32-year-old Norwegian named Anders Behring Breivik opened fire on participants in a Labour Party youth camp on the island of Utoya after exploding a bomb in Oslo, resulting in 77 dead, the worst tragedy in Norway since World War II.

English philosopher Thomas Hobbes famously argued in his 1651 book, Leviathan, that such acts of violence would be commonplace without a strong state to enforce the rule of law. But aren’t they? What about 9/11 and 7/7, Auschwitz and Rwanda, Columbine and Fort Hood? What about all the murders, rapes and child molestation cases we hear about so often? Can anyone seriously argue that violence is in decline? They can, and they do—and they have data, compellingly compiled in a massive 832-page tome by Harvard University social scientist Steven Pinker entitled The Better Angels of Our Nature: Why Violence Has Declined (Viking, 2011). The problem with anecdotes about single events is that they obscure long-term trends. Breivik and his ilk make front-page news for the very reason that they are now unusual. It was not always so.

Take homicide. Using old court and county records in England, scholars calculate that rates have plummeted by a factor of 10, 50 and, in some cases, 100—for example, from 110 homicides per 100,000 people per year in 14th-century Oxford to fewer than one homicide per 100,000 in mid-20th-century London. Similar patterns have been documented in Italy, Germany, Switzerland, the Netherlands and Scandinavia. The longer-term trend is even more dramatic, Pinker told me in an interview: “Violent deaths of all kinds have declined, from around 500 per 100,000 people per year in prestate societies to around 50 in the Middle Ages, to around six to eight today worldwide, and fewer than one in most of Europe.” What about gun-toting Americans and our inordinate rate of homicides (currently around five per 100,000 per year) compared with other Western democracies? In 2005, Pinker computes, just eight tenths of 1 percent of all Americans died of domestic homicides and in two foreign wars combined.

As for wars, prehistoric peoples were far more murderous than states in percentages of the population killed in combat, Pinker told me: “On average, nonstate societies kill around 15 percent of their people in wars, whereas today’s states kill a few hundredths of a percent.” Pinker calculates that even in the murderous 20th century, about 40 million people died in war out of the approximately six billion people who lived, or 0.7 percent. Even if we include war-related deaths of citizens from disease, famine and genocide, that brings the death toll up to 180 million deaths, or about 3 percent.

Why has violence declined? Hobbes was only partially right in advocating top-down state controls to keep the worse demons of our nature in check. A bottom-up civilizing process has also been under way for centuries, Pinker explained: “Beginning in the 11th or 12th [century] and maturing in the 17th and 18th, Europeans increasingly inhibited their impulses, anticipated the long-term consequences of their actions, and took other people’s thoughts and feelings into consideration. A culture of honor—the readiness to take revenge—gave way to a culture of dignity—the readiness to control one’s emotions. These ideals originated in explicit instructions that cultural arbiters gave to aristocrats and noblemen, allowing them to differentiate themselves from the villains and boors. But they were then absorbed into the socialization of younger and younger children until they became second nature.”

That second nature is expressed in the unreported “10,000 acts of kindness,” as the late Stephen Jay Gould memorably styled the number of typically benevolent interactions among people for every hostile act. This is the glue that binds us all in, as Abraham Lincoln so eloquently expressed it, “every living heart and hearthstone all over this broad land” through “the mystic chords of memory” that have been touched again by these better angels of our nature.