Evil repels analysis. Poets from the time of Homer have sung of war, but only a monster sings of atrocities. So, too, with journalism and scholarship. We are admonished not to ascribe rational motives to Osama bin Laden or Hitler, or to their followers. To admit of motives is to reduce the moral to the psychological, and thus to the comprehensible, and thus perhaps to the acceptable. Our understanding of unspeakable acts is limited on the one hand to the irreducible moral fact of evil, and on the other to the dynamics of mob psychology — of mass lunacy. But to exclude mass murder from the realm of conscious action offers an exculpation of its own, both to the killers and to ourselves — for how could we, ordinary folk who cherish life, descend to such madness? In this magisterial and profoundly disturbing “natural history” of mass murder, Daniel Jonah Goldhagen calls for an end to such willful blindness. As he did in his celebrated and controversial “Hitler’s Willing Executioners,” Goldhagen insists that even the worst atrocities originate with, and are then propelled by, a series of quite conscious calculations by followers as much as by leaders.

more from James Traub at the NYT here.