Proofs of a Conspiracy
John Robison was a Scottish scientist, who late in life wrote the one of the definitive studies of the Bavarian Illuminati, "Proofs of a Conspiracy". He was a contemporary and collaborator with James Watt, with whom he worked on an early steam car, contributor to the 1797 Encylopedia Britannica, professor of philosophy at the University of Edinburgh, and inventor of the siren.
Although Robison was very much an advocate of science and rationalism, in later life, disillusioned by the French Revolution, he became an ardent monarchist. In this work, "Proofs of a Conspiracy", Robison laid the groundwork for modern conspiracy theorists by implicating the Bavarian Illuminati as responsible for the excesses of the French Revolution. The Bavarian Illuminati, a rationalist secret society, was founded by Adam Weishaupt in 1776 in what is today Germany. They had an inner core of true believers, who secretly held radical atheist, anti-monarchist and possibly proto-feminist views, at that time considered beyond the pale. They recruited by infiltrating the numerous (and otherwise benign) Freemasonic groups which were active at the time on the continent. Necessarily they had a clandestine, compartmentalized, hierarchical organizational form, which has led some modern conspiracy theorists to identify them as the original Marxist-Leninist group. However, this is most likely simply a case of parallel evolution.