Proofs of a Conspiracy was written as a warning to Europe that the Jacobin forces which had conducted the French revolution from behind the scenes, were still active. Adam Weishaupt's illuminists had infiltrated wider Freemasonic circles.

Robison developed the narrative of the foundation of the Bavarian Illuminati in 1776, by the Jesuit trained Adam Weishaupt, a professor of canon law at Ignolstadt University and the subsequent suppression of the order by state and church authorities of Bavaria in 1785.

According to Robison after the order's suppression, the illuminists went underground across Europe infiltrating Masonic lodges or setting up their own lodges as a cover for their activities.

The Duke of Orleans headed illuminism in Paris through the Grand Orient Lodge, using it as springboard to subvert the ruling House of Bourbon. Whilst English and Scottish lodges managed to keep out most of the illuminists from their ranks, Robison asserted that some continental lodges were thoroughly under the sway of subversive illuminists and dangerous to the stability of Europe.

The intelligence agent monk, Alexander Horn, provided much of the structural detail of Robison's exposition of the Illuminati's fraternal structure and philosophy.