Once, the Russian queen invited the French philosopher Diderot to visit her court. Diderot tried to prove himself worthy of being invited by converting courtiers to atheism. Tired, the queen ordered Euler to shut the philosopher up. So Diderot was told that a learned mathematician had proved the existence of God by algebra, and if he wanted to listen, the mathematician would give this proof in front of all courtiers. Diderot accepted the challenge happily.
The next day, in court, Euler found Diderot and said solemnly in a very positive tone: "Sir, therefore God exists. Please answer! " For Diderot, this sounds reasonable. He was confused and didn't know what to say. The people around him laughed loudly, which made the poor man feel ashamed. He asked the queen to allow him to return to France immediately, and the queen agreed very calmly.
In this way, a great mathematician "defeated" a great philosopher by cheating.