On the basis of Hannah Arendt’s definition of ideology, I argue that we can conclude a distinction between ‘theory’ and ‘ideology’ and apply this to a characterisation of knowledge (claims) and critique. The problem and challenge is that there simply are differences in how political and academic knowledge claims are epistemologically built and discursively framed. These differences need to be accounted for analytically. If political analysts do not have the tools to distinguish knowledge claims and their validity, then we cannot separate, for instance, populist propaganda and the stigmatisation of so-called fake news from more trustworthy and evidenced knowledge and information. And if such distinction fails and knowledge claims are treated as equally valid, then political and social sciences become complicit with propaganda and level the way for intellectual and political distortions. We just need to engage and be concerned with this challenge and cannot escape it. As true as the observation is that theory always follows some interests and power ambitions, it is likewise true that there are different kinds of knowledge claims and knowledge production that we need to able to analytically identify and judge. Therefore, subsequently to introducing and summarising Arendt’s criteria, I discuss three conditions of critique and knowledge: Two deconstructive and one reconstructive condition. The deconstructive I exemplify with Hans Morgenthau’s notion of perspectivity (that he concludes from Karl Mannheim’s concept of Standortgebundenheit) and with the concept of negation as we find it in Herbert Marcuse; the reconstructive is illustrated with Eric Voegelin’s concept of noesis. The triangulation of these concepts results in a catalogue of normative conditions of critique. We can relate this catalogue back to the distinction between theory and ideology and achieve the argument that an epistemological tension must be maintained in political analysis and political action in order to not let political thought decline into ideology. The awareness of such epistemological tension is crucial to evaluate knowledge claims that appear to be fundamentally disrupted, politically in times of populism and academically in social sciences in times of an increasing speechlessness between, and idiosyncrasies of, research paradigms.