The article shows the extent to which recent populist movements challenge both liberal practice and liberal theory, and require a deeper reflection based on a history of ideas. To this end, I will first outline the current state of debate and name Carl Schmitt’s politically intervening thinking as a theoretical challenge. With reference to Hans Kelsen’s fundamental criticism of Schmitt, I will illustrate that the underlying political ontology becomes questionable in this debate. This ontology gains contour through the historical circumstances of the 1930s and the influence of Martin Heidegger’s neo-antique thinking. Against this background, a historically oriented analysis of Plato offers a way out of Heidegger’s metaphysical appropriation of the ancients, at the same time providing a way of overcoming the narrowness of current liberal discourse.