Conspiracism is a well-known topos in the history of humankind. Cassius Dio wrote about it as did anti-Judaic authors in the Middle Ages. Nevertheless, from the dawn of modernity until today, we have faced the rise of a new phenomenon. Pretty much on the eve of the French Revolution, conspiracists began to tell anti-Catholic and anti-masonic narratives down to the last detail. Jews, later on, became a recurring foe in those anti-modernist narratives. Conspiracism managed successfully to incorporate other forms of anti-modernism to form a fairly new form of thinking that I call "conspiracist ideology." While Enlightenment was the setting in which this amalgamation could take place, conspiracist ideology and its intellectual roots were characterized by a deep rejection of enlightenment thinking. The dialectical nature of conspiracist ideology is what makes it interesting from a historical perspective, in particular for the history of ideas.