Statistics is the continuation of politics by other means, to misquote Clausewitz. One hundred and fifty years after the crushing of the revolutionary Paris Commune, historians still clash aggressively about the death toll. Was it as high as 40,000 or as low as 10,000?

It matters because the Paris Commune is a shibboleth, a great left-wing site of memory and martyrdom, made famous by Karl Marx’s pamphlet The Civil War in France.