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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 Raisonn� des Sciences, des Arts et des M�tiers. The article Probabilit� published in it is attributed to him since it is unsigned.  The later Encyclop�die M�thodique 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 Anecdote" article by B. H. Brown, American Mathematical Monthly, Vol. 49, 302-303. The origin lies in a story related by Dieudonn� Thi�bault in his Mes Souvenirs de Vingt Ans de S�jour 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 pr�tendit que lui, et non l'imp�ratrice, en avait d'abord t�moign� le desir, et qu'il avait engag� le prince Galitzin, son ami, et ministre de Russie � Paris, � parler � cette souveraine de l'empressement avec lequel il irait mettre � ses pieds l'hommage de son admiration, de sa reconnaissance et de son respect: qu'elle avait simplement r�pondu que si M. Diderot faisait le voyage de Saint-P�tersbourg, elle le verrait volontiers; que l�-dessus il partit. Du moment o� il eut d�pass� les fronti�res de la Russie, il se trouva d�fray� de tout. Arriv� � P�tersbourg, il fut re�u et trait� � merveille par l'imp�ratrice, aussi charm�e de la f�condit� et de la chaleur de son imagination, de l'abondance et de la singularit� de ses id�es, qu'elle parut s'amuser du z�le, de la hardiesse et de l'�loquence avec lesquels il pr�chait publiquement l'ath�isme. N�anmoins quelques vieux courtisans, plus exp�riment�s ou plus faciles � alarme, repr�sent�rent et persuad�rent � cette souveraine autocrate, que ce genre de pr�dication pourrait avoir de f�cheux effets, � la cour surtout, o� une jeunesse nombreuse, destin�e aux premiers postes de l'empire, saisissait cette doctrine avec plus d'avidit� que d'examen. L'imp� ratrice, frapp�e de la convenance, de la n�cessit� m�me d'imposer silence � Diderot sur ces mati�res, voulut toutefois para�tre n'avoir aucune part aux moyens que l'on emploierait, d�fendit de faire intervenir l'autorit�, mais consentit � ce qu'on annonc�t au philosophe fran�ais qu'un philosophe russe, savant math�maticien, et membre distingu� de l'acad�mie, offrait de lui d�montrer l'existence de Dieu alg�briquement et en pleine cour. Diderot ayant t�moign� qu'il serait bien aise
d'entendre une d�monstration semblable, � la r�alite de laquelle au surplus il ne croyait gu�re, on prit jour et heure. Le moment �tant
venu, et en pr�sence de toute la cour, c'est-�-dire des hommes, et principalement des jeunes gens, le philosophe russe s'avan�a gravement vers son adversaire, et du ton de la conviction, lui dit: Monsieur, (a+b)n/z=x; donc Dieu existe: r�pondez.

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-P�tersbourg, 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 P�tersbourg, 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, indign�, voulut prouver la nullit� et l'ineptie de cette pr�tendue preuve, mais il ressentit malgr� lui l'embarras que produit
n�cessairement sur nous l'�vidence d'une sorte de mystification pr�par�e et concert�e: il ne put �chapper d'ailleurs � totalit� des plaisanteries auxquelles cette sc�ne donna lieu; enfin, inquiet, bless� de cette aventure, � laquelle Catherine ne pouvait �tre �tranger, il t�moigna le d�sir de retourner en France.

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 M�moires published in 1748 and these published in 1761