In 1776 Adam Weishaupt (1748-1830), professor of Canon Law at the University of Ingolstadt, founded a secret society that (after discarding the names of Perfectibilists and Order of the Bees) became known as the Order of the Illuminati. By attracting prominent members, it aimed to obtain important positions in society and thus to establish a moral regime that would lead all citizens back to the original state of liberty and equality. To this end, Weishaupt designed a graded organization based on elements taken from Freemasonry and the Jesuit Order (as he perceived it) and headed by a few higher degrees whose very existence was to remain unknown. Only this invisible inner circle was acquainted with the aims of the order; the lower degrees, whose understanding was deemed insufficient, were persuaded that less radical goals were pursued. The Illuminati tried to seize control of certain Masonic lodges to use them for propaganda and recruitment, a method that was to prove popular with many ninenteenth-century revolutionaries.

Due in large part to the efforts of Baron Adolph von Knigge (1752-1796), the future author of an immensely popular book of manners, Über den Umgang mit Menschen, the organization succeeded in the first half of the 1780s in expanding from Bavaria to the rest of Germany. It numbered between 1000 and 2000 members, among them several princes as well as intellectuals such as Goethe, Herder, and Pestalozzi. Yet it was discovered and outlawed in 1785, even though the official publication of many of its programs and other documents generated much publicity for its ideas. The Originalschriften exposed the Illuminati as living proof of how the Enlightenment conspired against the existing order and hence prepared the way for them to be accused, after the earthquake of the French Revolution, of being its subterranean cause. In 1797 the former Jesuit Augustin de Barruel (Mémoires pour servir à l'histoire du Jacobinisme) and the Scottish physicist John Robison (Proofs of a Conspiracy against All the Religions and Governments of Europe) published the two best known outlines of this conspiracy theory. In the years of bewildering revolution and unprecedented warfare their argument made a deep and lasting impression.

Read also the first application of the lessons of Barruel (Pdf 192 Kb).
Source: [Robert Clifford], Application of Barruel's Memoirs of Jacobinism, to the Secret Societies of Ireland and Great Britain, by the translator of that work, London: sold by E. Booker, 1798.

>> See also the report on the Illuminati by count Mirabeau in the chapter Jesuits.