D’Alembert, Jean le Rond (1717—1783)
The illegitimate son of the chevalier Destouches and a famous hostess, Mme. de Tencin, Alembert was named for the St. Jean le Rond church where he had been found on the steps. Diderot in approximately 1746 made him co-editor of the Encyclopédie, for which he wrote mathematical, literary, and philosophical articles. Because of his unorthodox views, however, he withdrew from the staff. Just the same, he was secretary of the French Academy (1772) and a leading representative of the Enlightenment.
His treatise on dynamics (1743) enunciated what is called d’Alembert’s Principle. He wrote an important history of the Academy (1787). Pensées philosophiques shows his freethought, as does his book on the Jesuits, Sur la destruction des Jésuites en France (1765), and the general rationalism of his Preliminary Discourse to the Encyclopédie. Alembert was one of Voltaire’s staunchest friends, and his work successfully made the Index Librorum Prohibitorum.
“As for the existence of a supreme intelligence,” he wrote to Frederick the Great, “I think that those who deny it advance far more than they can prove, and skepticism is the only reasonable course.” He goes on to say, however, that experience invincibly proves the materiality of the “soul.”
Joseph McCabe notes that d’Alembert “preferred to call himself a skeptic rather than an atheist, thinking that the latter implied an express denial of the existence of God . . . and he is convinced that the soul or mind is merely a function of the brain.”
D’Alembert’s last days were spent conversing with friends. He liked to hear others’ views as well as tell stories of his own. Said Condorcet, “He only was able to think of other subjects than himself, and to give himself to gaiety and amusement.”