This article examines the role of historical substance in online-published written conspiracy theories from an epistemological view. It describes how conspiracy theories are mediated in the digital age. It then shows the basic argumentative process of conspiracy theories, linking fictional and real events. It is a variation of the argumentative fallacy of the "post hoc fallacy," which we call the "post coniurationem fallacy." The historical narrative thus provides a plausible perspective and the appearance of veracity to the conspiracy narrative. This dynamic is supported by the rootedness of conspiracy theories in implicit memory. The case study of the Czech conspiracy website Aeronet illustrates this. The multiplicity of today's conspiracy theories and the ease with which they can be disseminated through digital media is thus profoundly transforming how parts of society encounter historical fabric and shape collective memory.