Good “King” Stanislas loved literature, had read Voltaire, was infected with Enlightenment. In 1749 he would publish his own manifesto, The Christian Philosopher, which his daughter the Queen of France would read with sad displeasure. She warned him that his ideas smelled strongly of Voltaire’s; but the old man relished the ideas as well as the wit of Voltaire; and as he too had a mistress (the Marquise de Boufflers), he saw no contradiction in making the poet a favorite at his court. Moreover, he appointed Émilie’s broad-minded husband grand marshal of his household at two thousand crowns a year.

Another officer, of Stanislas’ court was Marquis Jean François de Saint-Lambert, captain of the guards. Mme. du Châtelet had first met him in 1747, when he was thirty-one and she forty-one; it was a dangerous age for a woman whose lover had become only a devoted friend. By the spring of 1748 she was writing to the handsome officer love letters of almost girlish abandon. “Come to me as soon as you are dressed.” “I shall fly to you as soon as I have supped.” Saint-Lambert responded gallantly. Sometime in October Voltaire surprised them in a dark alcove conversing amorously. Only the greatest philosopher can accept cuckoldom graciously. Voltaire did not at once rise to the occasion; he reproached them volubly, but retired to his room when Saint-Lambert offered to give him “satisfaction”—i.e., to kill him at dawn. Émilie came to Voltaire at two o’clock in the morning. She assured him of her eternal love, but gently reminded him that “for a long time you have complained … that your strength abandons you.… Ought you to be offended that it is one of your friends who supplies your place?” She embraced him, called him the old pet names. His anger melted. “Ah, madame,” he said, “you are always right. But since things must be as they are, at least let them not pass before my eyes.” The next evening Saint-Lambert called upon Voltaire and apologized for his challenge. Voltaire embraced him. “My child,” he told him, “I have forgotten all. It was I who was in the wrong. You are in the happy age of love and delight; enjoy those moments, too brief. An old invalid like me is not made for these pleasures.” The next night all three supped together.83

This ménage à trois continued until December, when Madame decided she must go to Cirey to arrange her finances. Voltaire accompanied her. Frederick renewed his invitation; Voltaire was now inclined to accept it. But soon after her arrival at Cirey the Marquise confided to him that she was pregnant, and that, at her age, now forty-three, she did not expect to survive childbirth. Voltaire sent word to Frederick not to expect him, and asked Saint-Lambert to come to Cirey. There the three lovers devised a plan to secure the legality of the child. Madame urged her husband to come home to accelerate some business. He was not disturbed to find two lovers supplementing him; he enjoyed the hospitality they gave him. The Marquise put on all her charms of dress and caress. He drank, and consented to make love. Some weeks later she told him that she had indications of pregnancy. He embraced her with pride and joy; he proclaimed the expected event to all and sundry, and everyone offered him congratulations; but Voltaire and Saint-Lambert agreed to “class the child among Mme. du Châtelet’s miscellaneous works [œuvres mêlées]84 The Marquis and Saint-Lambert returned to their posts.

In February, 1749, Émilie and Voltaire moved to Paris. There she worked on her translation of the Principia, aided by Clairaut. Two letters to Saint-Lambert (May 18 and 20) reveal her character:

No, it is not possible for my heart to express to you how it adores you. Do not reproach me for my Newton; I am sufficiently punished for it. Never have I made a greater sacrifice to reason than in remaining here to finish it.… I get up at nine, sometimes at eight; I work till three; then I take my coffee; I resume work at four; at ten I stop.… I talk till midnight with M. de Voltaire, who comes to supper with me; at midnight I go to work again, and continue till five in the morning.… I finish the book for reason and honor, but I love only you.85

On June 10 Frederick, thinking Voltaire freed by Saint-Lambert from further responsibility for Mme. du Châtelet, urgently renewed his invitation to Potsdam. Voltaire replied: “Not even Frederick the Great … can prevent me from carrying out a duty from which nothing can dispense me.… I will not leave a woman who may die in September. Her lying-in has every likelihood of being very dangerous; but if she escapes I promise you, Sire, that I will come and pay my court in October.”86

In July he took her to Lunéville, where she could have proper medical attendance. The fear of death troubled her—to be taken off just when she had found love again, just when her years of study were to be crowned with the publication of her book. On September 4 she gave birth to a daughter. On September 10, after much suffering, she died. Voltaire, overcome with grief, stumbled out of her room, fell, and remained unconscious for some time. Saint-Lambert helped to revive him. “Ah, my friend,” said Voltaire, “it is you who have killed her.… Oh, my God, monsieur, what could have induced you to get her into that condition?” Three days later he asked Longchamp for the ring that had been removed from the dead woman’s hand. It had once held his own portrait; Longchamp found in it Saint-Lambert’s. “Such are women,” exclaimed Voltaire. “I took Richelieu out of that ring. Saint-Lambert expelled me. That is the order of nature; one nail drives out another. So go the affairs of this world.”87 Madame was buried at Lunéville with the highest honors of Stanislas’ court, and was soon followed by her child.

Voltaire and the Marquis retired to Cirey. Thence Voltaire replied to some letters of condolence from Paris:

You make my consolation, my dear angels; you make me love the unhappy remainder of my life.… I will confess to you that a house which she inhabited, although overwhelming me with grief, is not disagreeable to me.… I do not fly from that which speaks to me of her. I love Cirey; … the places which she embellished are dear to me. I have not lost a mistress, I have lost half of myself, a soul for whom mine was made, a friend of twenty years, whom I knew in her infancy. The most tender father loves not otherwise his only daughter. I love to find again everywhere the idea of her. I love to talk with her husband, with her son.88

And yet he knew that he would waste away if he remained a widower in isolated Cirey. He sent his books, scientific apparatus, and art collection to Paris, and followed them on September 25, 1749. On October 12 he established himself in the capital, in a spacious mansion in the Rue Traversière.

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