Claude Adrien Helvétius was a French philosopher, freemason and littérateur.
Helvétius was one of several French philosophes who spent time at the court of Frederick the Great of Prussia (depicted above)
François-Marie Arouet, known by his nom de plume M. de Voltaire, was a French Enlightenment writer, philosopher (philosophe), satirist, and historian. Famous for his wit and his criticism of Christianity and of slavery, Voltaire was an advocate of freedom of speech, freedom of religion, and separation of church and state.
Portrait c. 1720s, the Musée Carnavalet
Voltaire was imprisoned in the Bastille from 16 May 1717 to 15 April 1718 in a windowless cell with ten-foot-thick walls.
In the frontispiece to Voltaire's book on Newton's philosophy, Émilie du Châtelet appears as Voltaire's muse, reflecting Newton's heavenly insights down to Voltaire.
Pastel by Maurice Quentin de La Tour, 1735