home email

Denis Diderot

b. October 5, 1713, Langres, France
d. July 31, 1784, Paris

Denis Diderot is known predominantly for his role in creation of the great Encyclopedie or Dictionnaire Raisonné des Sciences, des Arts et des Métiers. The article Probabilité published in it is attributed to him since it is unsigned.  The later Encyclopédie Mèthodique includes an addition to the article absent, originally written by D'Alembert, by both Diderot and Condorcet.

For students of mathematics, however, Diderot is known for his supposed encounter with Euler at the Russian court . For this, see "The Euler-Dederot Anecdot" article by B. H. Brown, American Mathematical Monthly, Vol. 49, 302-303. The origin lies in a story related by Dieudonné Thiébault in his Mes Souvenirs de Vingt Ans de Séjour a Berlin. The extract given below is taken from the fourth edition, volume III, pp. 149-151 published in 1827. At right, is the English translation. 

Tout le monde a su, dans le temps, le voyage que Diderot fit en Russie. On prétendit que
lui, et non l'impératrice, en avait d'abord té-
moigné le desir, et qu'il avait engagé le prince
Galitzin, son ami, et ministre de Russie à Paris,
à parler à cette souveraine de l'empressement
avec lequel il irait mettre à ses pieds l'hom-
mage de son admiration, de sa reconnaissance
et de son respect: qu'elle avait simplement
répondu que si M. Diderot faisait le voyage de
Saint-Pétersbourg, elle le verrait volontiers;
que là-dessus il partit. Du moment où il eut
dépassé les frontières de la Russie, il se trouva
défrayé de tout. Arrivé à Pétersbourg, il fut
reçu et traité à merveille par l'impératrice, aussi
charmée de la fécondité et de la chaleur de son
imagination, de l'abondance et de la singula-
rité de ses idées, qu'elle parut s'amuser du zèle,
de la hardiesse et de l'éloquence avec lesquels
il prêchait publiquement l'athéisme. Néan-
moins quelques vieux courtisans, plus expé-
rimentés ou plus faciles à alarme, représentè-
rent et persuadèrent à cette souveraine auto-
crate, que ce genre de prédication pourrait
avoir de fâcheux effets, à la cour surtout, où
une jeunesse nombreuse, destinée aux pre-
miers postes de l'empire, saisissait cette doc-
trine avec plus d'avidité que d'examen. L'impé-
ratrice, frappée de la convenance, de la néces-
sité mème d'imposer silence à Diderot sur ces
matières, voulut toutefois paraître n'avoir au-
cune part aux moyens que l'on emploierait,
défendit de faire intervenir l'autorité, mais
consentit à ce qu'on annoncât au philosophe
français qu'un philosophe russe, savant ma-
thématicien, et membre distingué de l'aca-
démie, offrait de lui démontrer l'existence de
Dieu algébriquement et en pleine cour. Di-
derot ayant témoigné qu'il serait bien aise
d'entendre une démonstration semblable, à la
réalite de laquelle au surplus il ne croyait
guère, on prit jour et heure. Le moment étant
venu, et en présence de toute la cour, c'est-à-
dire des hommes, et principalement des jeu-
nes gens, le philosophe russe s'avança grave-
ment vers son adversaire, et du ton de la con-
viction, lui dit: Monsieur,
(a+b)n/z=x; donc Dieu existe: répondez.



Diderot, indigné, voulut prouver la nullité et
l'ineptie de cette prétendue preuve, mais il
ressentit malgré lui l'embarras que produit
nécessairement sur nous l'évidence d'une sorte
de mystification préparée et concertée: il ne
put échapper d'ailleurs à totalité des plai-
santeries auxquelles cette scène donna lieu;
enfin, inquiet, blessé de cette aventure, à la-
quelle Catherine ne pouvait être étranger, il té-
moigna le désir de retourner en France.
 

Everyone knew, in time, the trip that Diderot made to Russia. It was claimed that he, and not the empress, had first testified to the desire of it, and that he had engaged Prince Galitzin, his friend, and minister from Russia to Paris, by speaking with this sovereign about the eagerness with which he would put at his feet the homage of his admiration, his recognition and his respect: that she had simply answered that if Mr. Diderot made the trip to Saint-Pétersbourg, she would see it readily; that he left on this subject. From the moment when he had passed the borders of Russia, he was defrayed of all. Arrived at Pétersbourg, he was accepted and treated with wonder by the empress, so charmed by the fecundity and heat of his imagination, abundance and singularity of his ideas, that she appeared to be amused with the zeal, the boldness and the eloquence with which he preached atheism publicly. Nevertheless some old courtiers, more experienced or easier with alarm, represented and persuaded to this sovereign autocrat, that this kind of preaching could have annoying effects, at the court especially, where many youth, intended for the first stations of the empire, seized this doctrine with more greed than of examination. The empress, struck by convenience, of the necessity even of imposing silence on Diderot on these matters, wanted however to appear not to have any part with the means which one would employ, defended to make authority intervene, but granted so that one announced to the French philosopher that a Russian philosopher, scholarly mathematician, and distinguished member of the academy, offered to show the existence of God algebraically to him and in full court. Diderot having testified that it would be quite easy to hear a similar demonstration, with the reality of which moreover he scarcely believed, one took day and hour. The moment having come, and in the presence of all the court, that is men, and principally of young people, the Russian philosopher advanced seriously towards his adversary, and with the tone of the conviction, says to him: Sir,
(a+b) n/z=x; thus God exists: answer

Diderot, made indignant, wanted to prove the nullity and the ineptitude of this alleged proof, but he felt in spite of it the embarrassment which necessarily the obviousness of a kind of prepared and concerted mystification produces on us: he could not escape besides with totality from the pleasantries to which this scene gave place; finally, anxious, wounded by this adventure, to which Catherine could not be a stranger, he testified to the desire to return to France.

 

Kraker and Krueger in The Mathematical Writings of Diderot have discussed Diderot's other mathematical work. It consists of the following Mémoires published in 1748 and these published in 1761