Jean Le Rond d'Alembert (1717–1783) was a French mathematician, physicist, and philosopher who ranks among the leading figures of the Enlightenment. He is best remembered as co-editor, with Denis Diderot, of the landmark Encyclopédie, and for foundational contributions to mechanics and the theory of differential equations.[1]
Early life
D'Alembert was born in Paris on 16 November 1717, the illegitimate son of the writer Claudine Guérin de Tencin and the chevalier Louis-Camus Destouches. Abandoned as an infant near the church of Saint-Jean-le-Rond, from which he took his name, he was placed with a foster family, while his father quietly provided for his upbringing and education.[2] He studied at the Collège des Quatre-Nations, where he was drawn to mathematics and the sciences, ultimately turning away from the careers in law and medicine that his guardians had intended for him.
Mathematics and mechanics
In 1743 d'Alembert published his Traité de dynamique, in which he set out what is now known as d'Alembert's principle, a reformulation of the laws of motion that reduces problems of dynamics to problems of statics.[3] He made pioneering studies of the vibrating string, deriving the one-dimensional wave equation and its general solution, and he contributed to fluid dynamics, celestial mechanics, and the theory of differential equations. His name survives in d'Alembert's formula, the ratio test for infinite series, and the d'Alembert operator. He was elected a Fellow of the Royal Society and belonged to the principal learned academies of his day.
The Encyclopédie
From 1751 d'Alembert served alongside Denis Diderot as co-editor of the Encyclopédie, ou dictionnaire raisonné des sciences, des arts et des métiers, the vast collaborative work that became a symbol of Enlightenment thought. He wrote its celebrated Discours préliminaire (Preliminary Discourse), a survey of the state and interconnection of human knowledge, and contributed numerous articles on mathematics and the sciences.[1] Amid mounting controversy over the project—particularly after his article "Genève" provoked criticism—he withdrew from the editorship in 1758, leaving Diderot to carry the enterprise to completion.
Later years and legacy
D'Alembert was elected to the Académie française in 1754 and became its permanent secretary in 1772, a role in which he composed eulogies of deceased members. A prominent figure in the Parisian salons, he declined invitations from Frederick the Great of Prussia and Catherine the Great of Russia to preside over their academies, choosing to remain in Paris. He died there on 29 October 1783. He is remembered as one of the foremost mathematicians and philosophes of the eighteenth century, whose work helped shape both modern mechanics and the broader intellectual program of the Enlightenment.
