In dialogues, Diderot-Barthelemy dialogue is a purported to conversation between Denis Diderot, a self-proclaimed god believer and materialist who all but openly espoused atheism, and an Jean Barthelemy (1716-1795) (Ѻ), a French abbe (catholic clergyman), writer, and oriental language scholar, the text of which was written in 1772 and 1773, but not published (French) until 1921, on the subject of god, soul, and Christianity in general.
The so-called apocryphal text was found or rediscovered, in the early 20th century, among the papers of Charles Sainte-Beuve (1804-1869) (Ѻ), by Beuve’s secretary Jules Troubat (1836-1914) (Ѻ), who had intended to see the dialogue published within his reaction existence, but failed to realize as such. Albert Cim (1845-1924) (Ѻ), and associate of Troubat, however, had made a copy of the dialogue, and, after WWI, coordinated with Jean Finot, managing editor of Revue Mondaile, to get the dialogue published in the monthly review. A year later, Albert Messein, a publisher, who had just published a collection of anecdotes on the life of Diderot, worked with Cim to get the dialogue published as a thin volume. 
The following are selected sections from the dialogue: 
Barthelemy: In fact, for you Diderot, death is the end of everything.— — — — — — — — — —
Diderot: Don’t make me say that, Abbe. Don’t let us go so far. Although I might very well quote against you a certain legend, a corollary of the resurrection of Lazarus by the Christ: ‘What did you see down there, when you were dead?’ – ‘Nothing, Master; there is nothing,’ answered Lazarus. And Jesus whispered in his ear: ‘No, there is nothing; but do not tell.’
Barthelemy: Legend, assuredly! Pure legend!
Diderot: Agreed! But for myself, I hold to what we have before our eyes. Our soul, its essence, its origin, its destiny, what it will become after us, and in the very first place, if we really have one, … for, indeed, I don’t know. I can affirm nothing about it, and Ive and idea that those who speak so freely and so willingly about it ex cathedra do not know any more about it than I do.
Barthelemy: However, if you abolish the soul …
Diderot: I abolish nothing at all: I do not know.
Barthelemy: … you will have to abolish god.
Diderot: A virgin who receives the visit of a young man and a bird and who becomes pregnant, not by the young man, but by the bird; this virgin who bears a child and remains a virgin; this god who dies on the cross to appease god, then comes to life again and ascends into heaven (where, to heaven?), all that is mythology, my dear Abbe, it is paganism, it is worthy of Uranus, Saturn, and the Titans, Minerva springing full formed from the head of Jupiter, Juno pregnant with Mars from having breathed the perfume of a flower, Phoebus-Apollo driving the chariot of the sun … These are the same delirious adventures. Our friend d’Holbach freely declares that the supernatural does not interest him. No, it tells him nothing; it is an aberration, unreason. Isn’t it really folly, now, to go imagining that with the simple words, that is to say, moving the air with the tip of the tongue, one is going to change the laws of the universe and what one calls the decrees of providence?— — — — — — — — — —
Diderot: Does not the Bible, in Deuteronomy [13:6-11], command the massacre of those of our fellow-citizens who do not share our religious beliefs? (add)— — — — — — — — — —
Diderot: Well, would you believe, my dear friend, sometimes I suspect you of having, besides your profound learning, too much good sense not to be enlightened about the value of these Catholic dogmas, and to be decided, in this respect, just as I am? Naturally, you will not agree to this, and in your conscience you think me terrible indiscreet … But finally, yes—why are you a Catholic?
Barthelemy: What! Why?
Barthelemy: But …
Diderot: Well then, I’ll tell you. It is soley—soley!—because you were born in France and were brought up, ‘nourished’, by Catholics. Exactly! Suppose yourself for a moment a native of the Antipodes, of Aanzibar, of Cathay, of Patagonia, and see what would have become of you. You would be perhaps not even an Israelite, Lutheran, Calvinist, or Muslim but very likely a Buddhist, Brahmin, idolater, or animal-worshipper for all I know! We have the choice. You see, my dear Abbe, all that is an affair of latitude, a pure chance, luck.
“What is god but a word, a simple vocable to explain the existence of the world? And note well that after all, this word explains nothing.”— Denis Diderot (1773), “Dialogue with Barthelemy” 
“The word ‘god’, will rarely be found to designate more than the unknown cause of those effects which man has either admired or dreaded.”— Baron d’Holbach (1770), The System of Nature (pg. 207) 
“What then is a god, it is a name which expresses the unknown cause, the supposititious [sic] origin of all existence.”— Percy Shelley (1811), “Letter to Elizabeth Hitchener”, Jun 11 
“The importance of the dialogue in the life and thought of Diderot is apparent to anyone who has read it. In no other place has Diderot shown himself so clearly an anti-Catholic, anti-revelationionist; in no other place is he so unreservedly an atheistic materialist.”
— Robert Loy (1958), ““Notes on the Apocryphal Diderot Text”