Voltaire’s next destination was the Château de Cirey, on the borders of Champagne and Lorraine. The building was renovated with his money, and here he began a relationship with the Marquise du Châtelet, Gabrielle Émilie le Tonnelier de Breteuil (famous in her own right as Émilie du Châtelet). Cirey was owned by the Marquise’s husband, Marquis Florent-Claude du Chatelet, who sometimes visited his wife and her lover at the chateau. The relationship, which lasted for fifteen years, had a significant intellectual element. Voltaire and the Marquise collected over 21,000 books, an enormous number for the time. Together, they studied these books and performed experiments in the “natural sciences” in his laboratory. Voltaire’s experiments included an attempt to determine the elements of fire.
Having learned from his previous brushes with the authorities, Voltaire began his habit of keeping out of personal harm’s way, and denying any awkward responsibility. He continued to write plays, such as Mérope (or La Mérope française) and began his long research into science and history. Again, a main source of inspiration for Voltaire were the years of his British exile, during which he had been strongly influenced by the works of Sir Isaac Newton. Voltaire strongly believed in Newton’s theories, especially concerning optics (Newton’s discovery that white light is composed of all the colours in the spectrum led to many experiments at Cirey), and gravity (Voltaire is the source of the famous story of Newton and the apple falling from the tree, which he had learned from Newton’s niece in London and first mentioned in his “Essai sur la poésie épique”, or “Essay on Epic Poetry”).
Although both Voltaire and the Marquise were curious about the philosophies of Gottfried Leibniz, a contemporary and rival of Newton, they remained essentially “Newtonians”, despite the Marquise’s adoption of certain aspects of Leibniz’s arguments against Newton. She translated Newton’s Latin Principia in full, adjusting a few errors along the way, and hers remained the definitive French translation well into the 20th century. Voltaire’s book Eléments de la philosophie de Newton (Elements of Newton’s Philosophy), which was probably co-written with the Marquise, made Newton accessible to a far greater public. The Marquise also wrote a celebratory review in the Journal des Savants. It is often considered the work that finally brought about general acceptance of Newton’s optical and gravitational theories.
Voltaire and the Marquise also studied history, particularly those persons who had contributed to civilization. Voltaire’s second essay in English had been “Essay upon the Civil Wars in France”. It was followed by La Henriade, an epic poem on the French King Henri IV, glorifying his attempt to end the Catholic-Protestant massacres with the Edict of Nantes, and by a historical novel on King Charles XII of Sweden. These, along with his Letters on the English mark the beginning of Voltaire’s open criticism of intolerance and established religions. Voltaire and the Marquise also explored philosophy, particularly metaphysics, the branch of philosophy that deals with being and with what lies beyond the material realm such as whether or not there is a God or souls, etc. Voltaire and the Marquise analyzed the Bible, trying to discover its validity for their time. Voltaire’s critical views on religion are reflected in his belief in separation of church and state and religious freedom, ideas that he had formed after his stay in England.
In the fall of 1735, Voltaire was visited by Francesco Algarotti, preparing a book about Newton. In 1736 Frederick the Great started to write letters to Voltaire. Two years later Voltaire lived in Holland and became acquainted with Herman Boerhaave and ‘s Gravesande. In first half of 1740 Voltaire lived in Brussels and met with Lord Chesterfield. He went to see a dubious publisher Jan van Duuren in the Hague, because of the Anti-Machiavel, written by the crown prince, and ordered it back. Voltaire lived in Huis Honselaarsdijk belonging to his admirer. In September they met for the first time in Moyland Castle near Cleve; in November Voltaire went to Rheinsberg Castle for two weeks; in August 1742 Voltaire and Frederick met in Aix-la-Chapelle. Voltaire was sent to Sanssouci by the French government, as an ambassador/spy and find out more about Frederick plan’s after the First Silesian War.
Though deeply committed to the Marquise, Voltaire by 1744 found life at the château confining. On a visit to Paris that year, he found a new love–his niece. At first, his attraction to Marie Louise Mignot was clearly sexual, as evidenced by his letters to her (only discovered in 1937). Much later, they lived together, perhaps platonically, and remained together until Voltaire’s death. Meanwhile, the Marquise also took a lover, the Marquis de Saint-Lambert.