Abbe Augustin BarruelAbbé Augustin Barruél (February 10, 1741 - May 10, 1820) was a Jesuit priest mostly known for originally inventing the conspiracy theory involving the Knights Templars, the Bavarian Illuminati and the Jacobinians in his book Memoirs Illustrating the History of Jacobinism (original title Mémoires pour servir à l'Histoire du Jacobinisme) published in 1797.
His basic idea was that of a very big conspiracy dating back through time, with the aim of overthrowing Christianity. It was to inspire John Robison to write his book Proofs of a Conspiracy which extended the concept even further. This theory has grown wildly throughout history, and is still alive in several imaginative minds.
Among other things he called Adam Weishaupt "a human devil".