The famed encylopedist Denis Diderot was once invited to visit the Russian Court by the empress, Catherine the Great. To the embarrassment of his host and the rest of the court, he promptly launched into an animated defense of atheism. Reluctant to muzzle her guest directly, Catherine hatched a cunning plan. Diderot was informed that a learned mathematician had discovered an algebraical demonstration of the existence of God and would present it before the Court, if he wished to hear it. Diderot naturally consented. The mathematician Leonhard Euler duly appeared and gravely declared: "Monsieur, (a + bn)/n = x, therefore God exists!" The upshot? Diderot, entirely unschooled in algebra, was rendered speechless; peals of laughter erupted around the room; Diderot, greatly embarassed, asked for permission to return to France; and Catherine gratefully bid him adieu.
Sources
Thiebault, "Souvenirs de vingt ans de sejour a Berlin", 1804, in James Newman, The world of mathematics
