The notion that human violence is in decline has a powerful appeal, partly because it appears to be counter-intuitive.
According to Harvard psychologist Steven Pinker, we may be living in the most peaceful period in human history. In his new book, The Better Angels of Our Nature, he collected huge amounts of data to show that in every category of violence and crime, from murder and rape to war and genocide, the world is getting less violent.
Why is it so talked about? Simply put, the book captures the zeitgeist of the so-called Long Peace. But it may also be the perfect swansong for this unusual period.
While the book may conflict with a certain widespread pessimism, its thesis accords with the experience of many - at least those who grew up during the Long Peace in the West and the emergent wealthy Southeast Asian economies. These people have never personally known war. That is a historical anomaly.
Contrast the book with another one. In the late 1960s, another intellectual, Arthur Koestler, published The Ghost in the Machine. That book also captured something of the zeitgeist of his generation. He argues humanity's self-destructive nature is hard-wired into our brain. That is why the Western scientific revolution cumulated in thermonuclear weapons that threatened the species with extinction.
Many people thought the book accorded well with their experience of the world then. Koestler, an ex-communist, killed himself in 1983. He would never have guessed that in less than a decade, the fearsome Soviet Union would be no more, heralding a period of Western-inspired prosperity and democracy.
Given the never-ending financial crisis, a potential currency war, an emergent China and reassertive US, this period may be on its last legs. There is no reason to believe we cannot descend into another barbaric age.