Laplace, Napoleon and the hypothesis of the prime mover

This is a story nicely told by Augustus DeMorgan, the XVIIth Century mathematician famous for the DeMorgan Laws,

not (a or b) = (not a) and (not b)
not (a and b) = (not a) or (not b)

DeMorgan wrote this fragment in A budget of paradoxes:

"With the general run of the philosophical atheists of the last century the notion of a God was an hypothesis. There was left an admitted possibility that the vague somewhat which went by more names than one, might be personal, intelligent, and superintendent. In the works of Laplace, who is sometimes called an atheist from his writings, there is nothing from which such an inference can be drawn: unless indeed a Reverend Fellow of the Royal Society may be held to be the fool who said in his heart, etc., etc., if his contributions to the Philosophical Transactions go no higher than nature. The following anecdote is well known in Paris, but has never been printed entire. Laplace once went in form to present some edition of his "Systeme du Monde" to the First Consul, or Emperor. Napoleon, whom some wags had told that this book contained no mention of the name of God, and who was fond of putting embarrassing questions, received it with—"M. Laplace, they tell me you have written this large book on the system of the universe, and have never even mentioned its Creator." Laplace, who, though the most supple of politicians, was as stiff as a martyr on every point of his philosophy or religion (e. g., even under Charles X he never concealed his dislike of the priests), drew himself up and answered bluntly, "Je n'avais pas besoin de cette hypothese-la." Napoleon, greatly amused, told this reply to Lagrange, who exclaimed, "Ah! c'est une belle hypothese; ca explique beaucoup de choses."

It is commonly said that the last words of Laplace were, "Ce que nous connaissons est peu de chose; ce que nous ignorons est immense." This looks like a parody on Newton's pebbles: the following is the true account; it comes to me through one remove from Poisson. After the publication (in 1825) of the fifth volume of the Mecanique Celeste, Laplace became gradually weaker, and with it musing and abstracted. He thought much on the great problems of existence, and often muttered to himself, Quest ce que c'est que tout cela! After many alternations, he appeared at last so permanently prostrated that his family applied to his favorite pupil, M. Poisson, to try to get a word from him. Poisson paid a visit, and after a few words of salutation, said, "J'ai une bonne nouvelle a vous annoncer: on a recu au Bureau des Longitudes une lettre d'Allemagne annoncant que M. Bessel a verifie par l'observation vos decouvertes theoriques sur les satellites de Jupiter." Laplace opened his eyes and answered with deep gravity, "L'homme ne poursuit que des chimeres." He never spoke again. His death took place March 5, 1827.

"The language used by the two great geometers illustrates what I have said: a supreme and guiding intelligence —apart from a blind rule called nature of things—was an hypothesis. The absolute denial of such a ruling power was not in the plan of the higher philosophers: it was left for the smaller fry. A round assertion of the non-existence of anything which stands in the way is the refuge of a certain class of minds: but it succeeds only with things subjective; the objective offers resistance. A philosopher of the appropriative class tried it upon the constable who appropriated him: I deny your existence, said he; Come along all the same, said the unpsychological policeman."

Laplace's retort on the existence of God, "I did not have a need for this hypothesis", still resonates with me as the best answer to the question. But that is not the entire story that DeMorgan had intended to say... Here is DeMorgan's continuation:

"Euler was a believer in God, downright and straightforward. The following story is told by Thiebault, in his Souvenirs de vingt ans de sejour a Berlin, published in his old age, about 1804.

[...]

"Diderot paid a visit to the Russian Court at the invitation of the Empress. He conversed very freely, and gave the younger members of the Court circle a good deal of lively atheism. The Empress was much amused, but some of her councilors suggested that it might be desirable to check these expositions of doctrine. The Empress did not like to put a direct muzzle on her guest's tongue, so the following plot was contrived. Diderot was informed that a learned mathematician was in possession of an algebraical demonstration of the existence of God, and would give it him before all the Court, if he desired to hear it. Diderot gladly consented: though the name of the mathematician is not given, it was Euler. He advanced towards Diderot, and said gravely, and in a tone of perfect conviction: "Monsieur, (a + bn)/n = x, done Dieu existe; repondes!" Diderot, to whom algebra was Hebrew, was embarrassed and disconcerted; while peals of laughter rose on all sides. He asked permission to return to France at once, which was granted."