In the book, Barruel claims that the French Revolution was the result of a deliberate conspiracy or plot to overthrow the throne, altar and aristocratic society in Europe.

[2] The four volumes of the text were published in a number of languages and created a debate about the role of the philosophes, their ideas, and the Enlightenment in the French Revolution.

His dislike and hostility towards the philosophers was well known and well developed before 1789 as he had been on the editorial staff of the popular anti-philosophy literary journal Année littéraire decades before the Revolution.

[9] He sees the end of the 18th century as "one continuous chain of cunning, art, and seduction"[10] intended to bring about the "overthrow of the altar, the ruin of the throne, and the dissolution of all civil society".

[12] Barruel returned to the principal texts of the Enlightenment and found reasons to draw close links between the philosophism of the time and the anti-Christian campaigns of the Revolution.

[15] He alleged that Voltaire, Jean le Rond d’Alembert, Denis Diderot, and Frederick II, the King of Prussia, planned the course of events that led to the French Revolution.

They began with an attack on the Church where a "subterranean warfare of illusion, error, and darkness waged by the Sect"[16] attempted to destroy Christianity.

[17] Barruel believed the philosophes were important as the original villains that seduced the population and made Enlightenment, and subsequently revolutionary, ideals favorable.

[18] Barruel analyses and criticizes Montesquieu's The Spirit of Laws and Rousseau's Social Contract because the application of the ideas expressed in these books had "given birth to that disquieted spirit which fought to investigate the rights of sovereignty, the extent of their authority, the pretended rights of the free man, and without which every subject is branded for a slave - and every king a despot".

Barruel believed that the philosophes had created a lasting influence as their spirit survived through their writings and continued to promote anti-monarchical feelings within the Jacobins and the revolutionaries.

The destruction of monarchies in Europe led to the triumph of the Jacobins as they trampled "underfoot the altars and the thrones in the name of that equality and that liberty which summon the peoples to the disasters of revolution and the horrors of anarchy".

These groups were believed to have constituted a single sect that numbered over 300,000 members who were "all zealous for the Revolution, and all ready to rise at the first signal and to impart the shock to all others classes of the people".

Even after Johann Adam Weishaupt, the leader of the sect, was discovered and tried in court, the proceedings could not uncover the universal influence of the Illuminati and no steps were taken against the group.

[31] Barruel believed that the Revolution was caused by Voltaire, Rousseau and the other philosophes who conspired with secret societies to destroy Catholicism and the monarchy in France.

Barruel believed that the conspirators attempt to "imbue the minds of the people with the spirit of insurrection and revolt"[34] and to promote radicalism within all members of society.

[35] It contained "the most profligate and impious productions of Voltaire, Diderot, Boulanger, La Mettrie, and of other Deists or Atheists of the age, and this under the specious pretence of enlightening ignorance".

[36] Barruel believed the volumes of the Encyclopédie were valuable in controlling the minds of intellectuals and in creating a public opinion against Christianity and monarchy.

Barruel defined philosophism as "the error of every man who, judging of all things by the standard of his own reason, rejects in religious matters every authority that is not derived from the light of nature.

He identified Voltaire as the "chief", d’Alembert as the "most subtle agent", Frederick II as the "protector and adviser", and Diderot as its "forlorn hope".

[45] As a Catholic apologist of the religious and political status quo, Barruel downplayed his own Catholicism and presented himself as a neutral party within the radicalized debate surrounding the Revolution.

The reader of the Memoirs could have been any individual who doubted some of Barruel's inferences, but who would eventually be overwhelmed by the sheer weight of evidence against the Enlightenment and liberation movements.

At the end of the letter Burke added: "I forgot to say, that I have known myself, personally, five of your principal conspirators; and I can undertake to say from my own certain knowledge, that as far back as the year 1773, they were busy in the plot you have so well described, and in the manner, and on the principle you have so truly represented.

In England, the Scottish scientist John Robison published Proofs of a Conspiracy against All the Religions and Governments of Europe, carried on in the Secret Meetings of the Free Masons, Illuminati, and Reading Societies.

[49] The work, published in 1798, detailed a conspiracy that involved philosophes, Masons, and the Illuminati and their desire to "root out all the religious establishments and overturn all the existing governments of Europe".

Barruel's version of the revolution, which blamed specific men and pointed out a single cause, has been rejected by the majority of scholars, as the concept of a "master conspiracy" lies on the fringes of historical analysis.

Hofman shows how Barruel sought to prove that public politics, demanded by both the philosophes and the revolutionaries, could not in fact exist, as it was an illusion designed to create support for their private desire to control France.

[57] According to this view, Memoirs Illustrating the History of Jacobinism can be read as an attempt to understand the public appeal of the ideas of the Enlightenment and mass politics.

Even though Freemasonry became a target in the paranoid literature that blamed the Revolution partly on the activities of Masons, the work still had some historical value in regard to the group.

Margaret Jacob argues that Barruel's writings "offer a point of departure for understanding the relationship between the Continental Enlightenment, as it was lived in the clubs, societies, and lodges of the eighteenth century, and the outbreak of the democratic revolutions in the late 1780s in Amsterdam, Brussels, and most important, Paris.

The Memoirs contain all of the elements that continue to characterize conspiracy narratives today, including the argument that a hidden group is orchestrating world events behind the scenes, and an attempt to construct a direct lineage from the past to the present.