Steven Pinker, celebrated for his books on language and the workings of the mind, ventures into big history with his latest volume, "The Better Angels of Our Nature: Why Violence Has Declined." He unloads a truckload of evidence to argue that humans have been getting more peaceful, more cooperative and less murderous, on scales large and small, for quite some time. Among the reasons: civilization really has made us more civil. That might seem a surprising conclusion for a card-carrying evolutionary psychologist, but Pinker hasn't gone all liberal artsy on us. Historicity has a role to play, he says, but so do biology and game theory.