His historical and cultural clumsiness aside, Horgan seems increasingly unclear of his subject as the book goes on. Does war refer only to military conflict between nation-states, or also the actions of paramilitary groups, spats of social antagonism, or all inter-personal violence? What is to be gained by shrinking such a wide and complex field of interactions to a three-letter word? Besides, that is, making it easier for Horgan to answer with the even smaller word no.

“If we all want peace — and every sane person does — surely we’re smart enough to achieve it. Or rather, choose it,” Horgan writes, describing his overall task.

Unfortunately for idealists, violence is frequently a product of cold, rational calculation. A lack of smarts has nothing to do with it. Is this becoming a trend, these procrustean attempts to fit history within a progressive teleology? Oh, what hath Pinker wrought?