Building on recent work in the sociology of intellectual interventions, the study of cultural boundaries of science, and the role of ideas in politics, the article develops a theory of public epistemologies as argumentative tools people use to support or oppose political positions. Two prominent public epistemologies that have recently crystallized in Italian politics are taken as illustrations, with special attention paid to the role of two academics (an economist and an immunologist) turned public intellectuals. The article argues that the rise of populism in Italy has contributed to unusual alignments between political and epistemological positions, which has made questions about science and expert knowledge much more relevant in contesting and supporting political decisions.