Ferdinand Maria Baader (1747-1797)
Gotha Illuminati Research Base (here and here).
*10 February 1747, †1797, medical doctor, Book Censorship councillor, Munich, member of the Illuminati under the code name Celsus / Thomas
From my book Perfectibilists (p. 251):
Baader, Ferdinand Maria (1747 Ingolstadt, Germany – 1797 Augsburg, Germany)
A professor in Munich and physician to the Electress Dowager, Baader was also a member of the Bavarian Academy of Sciences in Munich. He was a member of the Munich Lodge Theodor zum guten Rat, and had joined the Golden and Rosy Cross in 1784 (alias, Athamas).
Baader was insinuated into the Illuminati in December 1778; a member of the Areopagites; Priest Degree in 1782; received the last degree of Rex or Man-King (Docetist).24 His alias refers to “Celsus the Platonist” in the 2nd century AD, a polemical writer against Christianity. Celsus attacked Christianity from the point of view of Judaism and philosophy, with an appeal to adopt paganism.
Elysium: Libertas, veritas, amicitia
F. M. Baader was obsessed with the prospect that the Illuminati could and should set up a colony in America (Ordername: Elysium). The first letter is dated June, 1780. Here’s my translation of Baader’s work on the Elysium project:
I’ve received your last letter from Manheim and the two from Frankfurt. The Sublime Chapter is very pleased with your diligence and assiduousness. My dear brother, what travel and adventure awaits! But rest assured your task will not be a thankless one; expect to settle with real brothers in Elysium, and after hardships, knowledge of yourself and your brothers will increase.
For the cause of Elysium, already three letters have been sent: one to Philadelphia, and two to Paris, addressed to [Benjamin] Franklin and [John] Adams. My daughter is steadfast, and does not wish to have an inactive, nor at the same time, troubled life, but to live with great simplicity, friendship, and freedom. Our motto is Libertas, veritas, amicitia [Liberty, Truth, Friendship].Markner et. al, Die Korrespondenz des Illuminatenordens, Band I: 1776-1781, 2005, p. 140 [emphasis in the original]
Another excerpt of a letter (Munich, 7/5/1780) from Baader to [Costanzo di] Costanzo–the other co-founder of the Lodge St. Theodor–who were both Areopagites in the Order:
The AMERICANS still have enough strength to defend themselves. But suppose that the English become absolute masters of America, which I think would never happen if we keep in mind the efforts of the Dutch against the Spaniards. But assume the worst. The English will need men to repopulate the depopulated lands which came about through civil war & its effect. They will be content to find people capable of establishing a new colony. Perhaps they will assign us a place not so far from civilized men, as is our wish. It matters not: augmented by new recruits we will establish new colonies: we will go forth, traversing mountains, form an establishment according to our tastes, live together as brothers and die in Wisdom. I have no doubt in finding a great quantity of capable men able to put our thoughts into motion. Don’t worry My Brother; I pray that you do not die on us, for we need you to be one of the first to kiss the fertile grasslands Elysium.ibid., p. 154
According to Illuminatus Friedrich Nicolai, Baader was “a loyal, honest, freethinking man and an enemy of all superstition.” He was a good recruit. Through him the Illuminati “gained influence at the Academy of Sciences and in the College of Book Censors,” writes Reinhard Markner (ibid., p. XVII).
In volume two of the Original Writings of the Illuminati – Nachtrag von weitern Originalschriften, welche die Illuminatensekte – Weishaupt disclosed to F. M. Baader, with diagrams, “an outline according to which we can, methodically and without much trouble, lead, with the largest number of men, the greatest Order to the best results.”
F. M. Baader and the Golden and Rosy Cross
One of the main instigations between the Illuminati and the Golden and Rosy Cross was the fact that Ferdinand Maria Baader was accepted in the Rosicrucians; they also found out he was a Member of the Illuminati (which was not allowed).
According to Adam Weishaupt:
One of the many driving-forces behind the Rosicrucian’s bitterness was the following incident. As is well known, these gentlemen like to attract good chemists into their society in order to learn from them what they claim to already know. Professor Baader was known to them as such a personage. After quite a long period of insinuating himself, the Professor finally yielded and was admitted to membership.  Immediately after his admission the enclosed (as Appendix E.) Oberbrüderliches Rescript (‘Superior’s Decision’) from the Director of the Munich Circle was read out to him in the presence of the other Brethren. The Professor’s statement in response also appears below in the same Appendix, from the content of which the reader will readily see that he can hardly be said to have won thereby the love and friendship of the Brothers of the Golden and Rosy Cross. When other attacks on this system were published which contained expressions that bore some resemblance to Baader’s statements, the Professor became, in their eyes, the likely author, and the Illuminati were consequently seen as their enemies.Adam Weishaupt, Complete History Of The Persecution Of The Illuminati In Bavaria [Vollständige Geschichte Der Verfolgung Der Illuminaten In Bayern], pp. 106-7 [my emphasis]
Badder’s reply to his eventual rejection into the Golden and Rosy Cross, is reprinted in Weishaupt book:
REPLY [by Baader] TO THE SENIOR DIRECTORATE OF THE ROSICRUCIANS.
Was it astonishment or mere bewilderment that overwhelmed me when Circle. Director N. advised me of the order made by the Senior Directorate and read it out in the presence of Brothers N. and N.?
How amazed I was by your contempt for something with which you have no familiarity, and about which you know nothing except its name, a contempt inspired by the abject behaviour of a conspicuous traitor.
How must expressions like bogus society or deluded counterfeit organisation strike an accepted Mason?
What must a man of honour feel when he is told that he seeks to seduce well-meaning but credulous confreres?
And how ridiculously audacious the command to immediately lay aside the fatal gavel must sound!
Who on Earth can forbid me to correspond with an intimate friend (whom not only I but everyone else knows to be a man of the  highest honesty and integrity) on matters that they do not understand, matters that are not my private business but the business of several people and of my superiors.
How disgracefully rude to dishonour with the degrading name of Mr. Emissary a gentleman and Mason who travels to conduct business on behalf of his friends and several Lodges. How appalling that the lack of your own inner honour and integrity makes you question the honour and integrity of others, given your reference to ‘seducers’ and ‘emissaries’.
And finally, what a wretched style of writing, worthy of a budding muster-master83 or a municipal lawyer from the last century!
Those were my feelings, which I intended to set down on paper with the greatest sincerity and thus conclude this letter at this point, but certain circumstances force me to say more.
Since you are so pathetically ignorant about the so-called ‘lodges’ of the Illuminati, let me give you some information about them. 
I must, however, make it clear in advance that I do not ‘lead its Directorate’, but actually recognise other people as my superiors, just as the Worshipful Master of a Lodge repeatedly receives orders from other directing Brethren and then carries them out.
The word Illuminati means ‘enlightened ones’, so they correspond to what are known in the Rite of Strict Observance as graduate Mäurer, i.e. ‘graduated masons’. Due to their greater insight they can safely be entrusted with the education and preparation of the younger Brethren. The Illuminati are therefore – – – –84 but the Rosicrucians must already know this for themselves by means of their divine magic or cabbalistic calculations! Of this however I am convinced: they are not deluded counterfeiters (as Your Honour likes to jest in a tone plausibly reminiscent of a Clerk of the Court) but are genuinely enlightened men, for it was from them and through them I learned in advance that I would not get from you, my dear Rosicrucians, anything of what you pretend and promise.
I joined the society of Rosicrucians purely to maintain peace and unity within our Lodge (although I could well have done without such useless expenditure), but  how astonished I was when I saw that people whom I had believed were true to their oaths were holding irregular lodges, conferring M * * 85 Degrees, and even promoting M * *86 from other lodges to higher Degrees. Such a thing is incompatible with my official standing in the Lodge, with my position as a representative of the sublime Mother Lodge, and with my obligations.
For the above reasons I am taking this opportunity to resign, eagerly and with pleasure, and with the most valuable assurance of eternal silence, especially with regard to those secrets from the betrayal of which a certain ‘Senior Directorate’ will remain immune for a long time to come for, just between us, they have – – – – precisely none.
I am also happy to ignore your insults, reeking as they do of the language of the chancery and the civil service, and can assure you that neither our august Mother Lodge nor our Lodge here (and still less myself, who is just a member and Master pro tem of this Lodge) need ‘emissaries’ to seduce the credulous, least of all the members of your so-called sanctified (but certainly not  sanitised!) fraternity, since people whose brains you have burned and whose minds you have driven mad are generally unfit for those other societies where a love of truth and a desire for knowledge prevail.
I would ask a Very Venerable Senior Directorate if they are not in fact themselves deluded to allow this little essay of mine to reach the deluders.
[F. M.] Baader (ibid,, pp 265-9) [emphasis in original]