If the history of ideas told a sensible story, the enduring lesson of the cold war would be that fighting and winning a nuclear war is at best a futile proposition but more likely an insane one. Alas, history is never sensible. As Ron Rosenbaum reminds us in his new book, How the End Begins, ideas thought to be well past their expiration date have a strange way of reviving themselves. “The threat of nuclear war is back,” he warns, “and we have to face it again.” Rosenbaum memorably wrote about the subject for Harper’s more than thirty years ago; contrary to all rational expectations, not much