Surely anyone who does monstrous things must be a monster? Initially, most psychologists claimed that the Nazis and their ilk had a particular personality type – an authoritarian personality – which led them to follow strict leaders and to scapegoat and brutalize groups that were powerless and marginal.

In society at large, this idea was dealt a powerful blow by the trial in Jerusalem of Adolf Eichmann – one of the Nazis responsible for organizing the extermination of the Jews.

At Eichmann’s trial everyone expected to see a sadistic brute. But instead they were confronted by a mild and unassuming little man – the image of a colourless bureaucrat.

Hannah Arendt, an influential commentator who attended the trial, observed that the truly frightening thing about Eichmann was that he seemed just like the rest of us. This suggested that you don’t have to be an exceptional person to do exceptional evil. As she famously put it, Eichmann embodied the “banality of evil”.

Since then, historians have claimed that those who committed atrocities were no different from most of the German population. They were simply ‘ordinary men’.

Adolf Eichmann on trial in Jerusalem in 1961

Adolf Eichmann on trial in Jerusalem in 1961