Fascism, Hannah Arendt claimed in 1945, has invented a way of “lying the truth”. She later came to call this invention the modern political lie, and saw it as a key element in the event of totalitarianism. The present study explores a paradoxical relation between politics and truth in totalitarian movements that can reinvent itself anew, in non-totalitarian forms and under non-totalitarian conditions. Although Martin Heidegger is not a proponent of the modern political lie, the problematical relation between politics and truth, which Arendt addressed in her work, is present in his political writings from the 1930s. While parts of Arendt’s analysis remain implicit, they can be made explicit against the background of Heidegger’s writings. By studying together Heidegger’s political works and Arendt’s writings on totalitarianism, it is possible to shed light on a problem of politics and truth that can appear again, in contemporary democracies. For Arendt the problem of the modern political lie could not be countered by demanding more truthfulness or fact-checking in politics. What we must instead ask is: what position can truth and facts have in the political realm? Arendt herself embarked upon such a questioning in works after The Origins of Totalitarianism. There, she can be seen as developing a new concept of truth, partly in response to the problem of politics and truth in totalitarian movements. The aim of the present study is to explore the relation between politics and truth in Heidegger and Arendt respectively, as well as with regards to the relation between their works. Anna-Karin Selberg is a writer and researcher in philosophy at Södertörn University. This is her doctoral dissertation.