Only after Voltaire had solemnly sworn to preserve the peace, was he allowed to return to Potsdam.  Keeping the peace was not, however, in harmony with Voltaire’s character; plotting was a necessity with him; he could not resist it.

After he had succeeded in setting Arnaud aside and compelling him to leave Berlin, he turned his rage and sarcasm against the other friends of the king.  One of them was removed by death.  This was La Mettrie; he partook immoderately of a truffle-pie at the house of the French ambassador, Lord Tyrconnel, and died in consequence of a blood-letting, which he ordered himself, in opposition to the opinion of his physician.  He laughingly said, “I will accustom my indigestion to blood-letting.”  He died at the first experiment.  His death was in harmony with his life and his principles.  He dismissed the priest rudely who came to him uncalled, and entreated him to be reconciled to God.  Convulsed by his last agonies, he called out, “O my God!  O Jesus Maria!”

“He repents!” cried the delighted priest; “he calls upon God and His blessed Son.”

“No, no, no, father!” stammered La Mettrie, with dying lips; “that was only a form of speech.” [Footnote:  Nicolai, p. 20.]

Voltaire’s envy and jealousy were now turned against the Marquis d’Argens, who was indeed the dearest friend of the king.  At first he tried to prejudice the king against him; he betrayed to him that the marquis had privately married the actress Barbe Cochois.

The king was at the moment very angry, but the prayers of Algarotti, and the regret of the poor marquis, reconciled him at last; he not only forgave, but he allowed the marquise to dwell at Sans-Souci with her husband.

When Voltaire found that he could not deprive the marquis of the king’s favor, he resolved to occasion him some trouble, and to wound his vanity and sensibility.  He knew that the marquis was an ardent admirer of the French writer Jean Baptiste Rousseau.  One day Voltaire entered the room of the marquis, and said, in a sad, sympathetic tone, that he felt it his duty to undeceive him as to Jean Baptiste Rousseau, to prove to him that his love and respect for the great writer were returned with the blackest ingratitude.  He had just received from his correspondent at Paris an epigram which Rousseau had made upon the marquis.  It was true the epigram was only handed about in manuscript, and Rousseau swore every one who read it not to betray him; he was showing it, however, and it was thought it would be published.  He, Voltaire, had commissioned his correspondent to do every thing in his power to prevent the publication of this epigram; or, if this took place, to use every means to excite the public, as well as the friends of the marquis, against Rousseau, because of his shameful treachery.

At all events, this epigram, which Voltaire now read aloud. to the marquis, and which described him as the Wandering Jew, was as malicious as it was mischievous and slanderous.  The good marquis was deeply wounded, and swore to take a great revenge on Rousseau.  Voltaire triumphed.