Hannah Arendt's most ingenious philosophical idea was to transform Heidegger's ontological difference of being ( Sein ) and existing ( Seiende ). Whereas for Heidegger existing was founded in being as the origin of all meaning, for Arendt existing, in the form of the concrete historical praxis of ‘political animals’ in space and time (as she suggests in Vita Activa ), founds being. This is exemplified in modern revolutionary praxis as in the French and American Revolutions (as she suggests in On Revolution ). The problem then becomes that of maintaining the original revolutionary power in a power-founding constitutional order.