Alembert, Jean Le Rond d'

(1717-1783)

   philosopher, writer, physicist, and mathematician

   A major figure of the Enlightenment, jean Le Rond d'Alembert was born in paris, the natural son of the writer claudine guerin de tencin. With diderot,he was one of the authors of the Encyclopédia, in which he edited the Discours préliminaire (1751), as well as numerous scientific and philosophical articles, all marked by the spirit of the Age of Reason. using the three principles of Newton, d'Alembert also wrote his most important work, a treatise on physics and the science of mechanics, Traité de dynamique (1743), in which he describes movement and equilibrium between two bodies, and presents the principle that bears his name (the resultant of the forces impressed upon a system is equivalent to the effective force of the entire system). in the following works (Traité de l'équilibre et du mouvement des fluides, 1744; Théorié générale des vents, 1745), his studies led to the first conception of the calculus of partial differential equations. In Précession des équinoxes (1749), he proposed the first analytical solution to the precession of the equinoxes. He also discovered the theorem that bears his name, in which all algebraic equations have at least a real or an imaginary root. His other writings include Éléments de musique (1752), Mélanges de littérature et de philosophie (1753), and Éloges académiques. A rationalist, he opposed religious absolutism and spoke out for tolerance and for the access to scientific knowledge for all. His correspondence with voltaire was published by condorcet. D'Alembert was elected to the Academy of Sciences in 1741 and to the Académie Française in 1754.