Claude S. Fischer in the Boston Review:
Pinker makes three strategic moves in explaining the drop in violence. First, he considers every kind of violence—even metaphoric violence, such as racist attitudes—as a single entity. Thus, he needs all expressions of violence, from genocide to spanking, to decline, and all of these declines need to follow a common story line. A more timid author might have been satisfied with explaining just the decline of, say, war. And a more timid author might worry that a nuclear exchange between India and Pakistan would destroy the whole analysis overnight.
Second, Pinker takes on the burden of explaining every fluctuation and nuance in violence trends. He doesn’t let a jitter in his graph line go as random noise. The notable exception seems to be those two quasi-random world wars. Yet, elsewhere, he cannot help but try to make sense of each with ad hoc accounts, for instance by digging into Hitler’s personality. Total explanation is a heavy task.
Third, Pinker tries to sweep together virtually every explanation for violence or peace that anyone has ever proposed—and more—including schooling, brain lesions, humanitarianism, secularism, feminization, codes of honor, commerce, book publishing, and even the Great Man Theory of history (Hitler, Stalin, Mao). Some explanations he dismisses—for example, that affluence reduced the motives for violence, that nuclear weapons ended large-scale war, and that Roe v. Wade lowered crime rates in America. But his remaining list of explanations is long and eclectic.