This study argues that the bond between ‘secularization’ and ‘de-legitimation’ is not only borne out in debates over grand historical narratives relating to the status of modernity, as argued by Hans Blumenberg, but in debates over the appraisal of specific modern philosophical programs as well. It does this by examining how the category of ‘secularization' is used to delegitimize Martin Heidegger's thought, from both theological and secular perspectives, by two of his former students, Hans Jonas and Karl Löwith. By analysing (...) their interpretation of Heidegger and their understanding of secularization, legitimacy, and the philosophy-theology relationship, this study sheds light on the intellectual projects of these three thinkers – master and two students – and demonstrates the application of secularization as a hermeneutical category of de-legitimization on the basis of ‘insufficiency’ – either insufficiently secular or insufficiently religious. (shrink)