Historically, the human race has always depended on a reductionist approach to morality – one that helps us to clearly delineate the difference between good and evil. From the Cold War to the Crusades, societies have elected to believe that their enemies represent an absolute evil – an idea often strategically encouraged by the powers that be. However, the reality is that even the most abhorrent of evil acts, from rape to genocide, are committed by everyday human beings like you and I (a phenomenon for which Hannah Arendt coined the term, the “banality of evil”). This unsatisfying truth is the subject of Joshua Oppenheimer’s The Act of Killing, one of the finest documentaries I have ever come across.

A brief history lesson to begin. In 1965, the Indonesian government was subject to a failed coup that saw the military respond violently by executing more than 500,000 people with…