
Left: Photo of Holbach’s second mansion, Le Château de Grand-Val (Ѻ), where he ran his famous intellectual salons, and where, supposedly, the Hume-Holbach dinner party (1763) encounter occurred. Right: a photo of Voltaire, and others, at an earlier 1750s coffee house salon meeting.

In anecdotes, Hume-Holbach dinner party refers to the famous 1763 dinner party encounter between Scottish philosopher David Hume, an Epicurean-defending "quite atheism" leaning agnostic-skeptic, and French "extreme atheism" philosopher Baron d’Holbach, attended by sixteen other of the brightest minds of the century, retrospectively classified as “doubt’s greatest coming-out party” (Hecht, 2003).

Famous atheist moments
The Hume-Holbach dinner party collision (1763) might rank second in fame, in atheist circles, behind the Napoleon-Laplace anecdote (1802).

Overview
In the 1750s, in Paris, salons, i.e. coffee-fueled intellectual meet-ups, began to become popular; shown adjacent is a circa 1750 image of a discussion at Café Procope, showing: at rear, from left to right: Marquis Condorcet, Jean-Francois de La Harpe, Voltaire, with his arm raised, and Denis Diderot. [5]

In the 1760s, Baron d’Holbach, at his second mansion Le Château de Grand-Val (pictured above), outside of Paris, ran a bi-weekly intellectual salon, one of the most famous of all intellectual salons, with the entice of excellent food, expensive wine, and a library of over 3000 volumes, he attracted many notable visitors, including: Denis Diderot, Grimm, Condillac, Marquis Condorcet, Jean D'Alembert, Marmontel, Turgot, La Condamine, Helvetius, Jean-Jacques Rousseau, Adam Smith, David Hume, and Benjamin Franklin. [4]

In 1763, Hume (aged 52) (IQ:180|#111) visited Paris, a point in time, when most of his works were well-known and he was the toast of the town, during which time he visited the house of Baron d’Holbach (aged 40) during which time a “legendary dinner party” was thrown.

The following five people, among a total of eighteen at the dinner table, were known to have been in attendance, resulting in a "collision of social Newtons", so to say, in hmolscience speak:

1. Baron d’Holbach (aged 40) (IQ:185#|56) [SN:21], aka “Newton of the atheists” (Martin Priestman, 2000) (Ѻ) (V|1:45)
2. David Hume (aged 52) (IQ:180|#111) [RGM:111|1,250+] [SN:47], aka “Newton of moral sciences” (John Passmore, c.1960) (Ѻ) (Michael Foley, 1990)
3. Denis Diderot (aged 50) (IQ:170|#238) [RGM:463|1,250+], aka “first encyclopedist” [4]
4. Voltaire (age 69) (IQ:195|#18) [RGM:33|1,250+], aka “Prophet of Newtonian physics based Biblical-deistic reason” (Ching-Yao Hsieh, 1991)
5. Charles Montesquieu (age 74) (IQ:175|#200) [RGM:92|1,250+] [SN:51], aka “Newton of sociology” (Crane Brinton, 1950) (Ѻ)


Holbach	Hume	Diderot	Voltaire	Montesquieu
The five big chiefs at the Holbach-Hume dinner party (1763) encounter, where at Hume famously stated he "did not believe in atheists", because he had never seen one, to which Holbach replied: "look around, there are 18 of us, 15 are atheists, 3 have not made up their mind".

The gathering has been described as an salon-style philosophical dinner. Diderot related the encounter, between the great agnostic-leaning-atheist Hume, seated next to the extreme atheist d’Holbach, as follows: [1]

Hume: “I do not believe in atheists, because I have never seen one!”

Holbach: “Count how many we are here. We are eighteen.”

Holbach: “It is not too bad a showing to be able to point out to you fifteen at once; the three others have not mad up their minds.”

Ernest Mossner (1954) has described Holbach’s group as an “atheistical club”. [2] David Berman (1988) has argued that Hume took it into his head to make this remark per reason that his “opening gambit was rather like a Masonic handshake: an attempt to elicit a response from, and communicate with, someone whose secret identity he guesses.” [1] Jennifer Hecht (2003) dubs this “doubt’s greatest coming-out party”. [3]


A BBC segment on the Hume-Holbach dinner party collision.

A BBC segment on the Hume-Holbach dinner party collision.

Quotes
The following are related quotes:

“This [Holbach-Hume meeting] was the first group of actual avowed atheists; no dissembling, no caveats, just no gods, no god, nothing like it. For the first time, doubters were silenced neither by fear of being killed or exiled nor for fear of how the masses would behave if they became convinced if there was no god and no hell. The crowd believed morality was available to anyone through reason. The central text here was Holbach’s System of Nature.”
— Jennifer Hecht (2013), Doubt: a History (pg. 353); note: the above “central text” citation is an anachronism; per reason that Holbach’s System of Nature wasn’t drafted until c.1768, and not published until 1770

See also
● Heisenberg-Pauli dialogue
● Einstein-Murphy dialogue
● Moreland-Strobel dialogue

References
1. (a) Berman, David. (1988). A History of Atheism in Britain: From Hobbes to Russell (pg. 101). Routledge. 2013.
(b) Hecht, Jennifer M. (2003). Doubt: A History: The Great Doubters and Their Legacy of Innovation from Socrates and Jesus to Thomas (party, pg. 352). HarperOne.
2. Mossner, Ernest C. (1954). The Life of David Hume (atheistical club, pgs. 467). Publisher.
3. Hecht, Jennifer M. (2003). Doubt: A History: The Great Doubters and Their Legacy of Innovation from Socrates and Jesus to Thomas (party, pg. 352). HarperOne.
4. Blom, Philipp. (2010). A Wicked Company: the Forgotten Radicalism of European Enlightenment (abs). Basic Books.
5. (a) Age of Enlightenment – Wikipedia.
(b) Café Procope – Wikipedia.