This paper develops a critical argument about the generation of non-knowledge and structural amnesia arising from a prevalent American style of theoretical explanation of conspiracy theories. As a re-examination seeking a better starting point for how conspiracy theories have been known in theory, this is taken to be about what’s at stake when we take our analytic purview, who gets attended to and cited, what gets forgotten. Of greatest critical concern is how this ‘conspiracy theory theory’ has led to structural amnesia – a culturally privileged US-centric way of nonknowing that, this paper argues, persists in the face of strong empirical continuities and readily available sources and comparisons. Among these forgotten theories is Franz Neumann’s testable hypotheses about false concreteness, the presence of societally grounded anxieties wherever they resonate, and that conspiracy theories are a structural feature of fascist politics, then and now.