What kind of human beings can they be, who stand in a line and behead kneeling prisoners all together in a murderous ballet? Who put a man in a cage and set fire to him? Who throw homosexuals off a high building? Who get a twelve-year-old boy to shoot dead a 19-year-old? And who make videos for the world to see how they glory in their cruelties? The Islamic State, the new caliphate, is a textbook example of psychopaths treating evil as though it were normal. The fear that people at first feel has to turn into self-preservation. All the old codes and taboos that have been the source of good behavior break down fast, and vanish.

Hitler’s takeover of Germany is a recent precedent of a society breaking down and turning psychopathic. Huge numbers of men and women carried out mass-murder and genocide on behalf of Hitler. What encouraged them to do it? Adolf Eichmann is a particular case study. The organizer of mass-murder, he boasted that he would go laughing to his grave because he had been responsible for the death of 6 million Jews. After the war he escaped to Argentina. In a famous exploit, Israeli agents traced him, kidnapped him, and brought him to trial in Jerusalem. His defense was that he had been a mere bureaucrat, obeying the orders of his superiors.

In a book reporting on this trial, Hannah Arendt took Eichmann at his word. A phrase of hers describing his career, “the banality of evil,” has become a cliché. It was pretty unconvincing, given the evidence heard in the courtroom. Bettina Stangneth, a German academic, has just published Eichmann Before Jerusalem, a book that hardly mentions Hannah Arendt but is nonetheless a total and invaluable demolition job of her thesis. Thorough painstaking research shows that Eichmann had taken the lead in these crimes, was proud of it, and used friendship with other former Nazis in exile to build up credit and a reputation. His portrayal of himself as a humble bureaucrat was a lie that he hoped would allow him to escape the gallows.

Eichmann, then, was a psychopath for whom evil was not just normal but praiseworthy. It took a world war to stop him, and even so someone as intelligent as Hannah Arendt let him off the hook. Only war will put a stop to Islamic State, and already anyone who condemns its inhumanity is likely to meet with cries of “Islamophobia.”