There is a story, universally known to mathematicians, about Leonhard Euler, Denis Diderot, Catherine the Great, and the epistemological authority of mathematics. It apparently first appeared in English in Augustus De Morgan‘s book A Budget of Paradoxes:
Diderot paid a visit to the Russian Court at the invitation of [Catherine the Great]. 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 councillors 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, $\frac{(a + b^n)}{n} = x$, donc Dieu existe; repondez!1 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.2
