Alembert, Jean Le Rond d’

Alembert, Jean Le Rond d’ (1717-83): French, Mathematician and Philosopher.

Jean Le Rond d’Alembert was one of the most respected mathematicians and philosophers of 18th-century France. He began his career in geometry and quickly moved into developing mathematical models and applications for system mechanics and dynamics. He also became the first editor of Diderot, Denis’s Encyclopédie and ascended to the French Academy in 1754.

The illegitimate son of the French writer Claudine Guérin de Tencin, d’Alembert began life as a foundling on the steps of the Chapel of Saint Jean Le Rond in Paris. His education at the Collège Mazarin launched him into a career as a mathematician and later a philosopher, despite the Jansenist fathers’ wishes to the contrary. His groundbreaking work in mathematics and on the Encyclopédie led him to close relationships with Voltaire, François-Marie Arouet de and Frederick II, the Great of Prussia.

D’Alembert’s early work in integral calculus, mechanics, and partial differential equations were a watershed in the advancement of mathematics. His first publication, Mémoire sur le calcul intégral, appeared in 1739. Over the next few years, he would write important treatises on major topics of the day, including dynamics and wind. He published Traité de dynamique in 1743, in which he demonstrated “D’Alembert’s Principle” about the relationship between forces inside and outside of a physical system. In 1746, he received the Berlin Award for Science for his Réflexions sur la cause générale des vents and was elected to the Berlin Science Academy. In this latter work, he introduced the mathematical concept of partial differentiation.

In the 1740s, after establishing himself as one of Europe’s foremost mathematicians, d’Alembert became involved with Diderot’s Encyclopédie as editor and contributor. In 1746, d’Alembert began work as primary articles editor on Diderot’s Encyclopédie. His greatest contribution to the project at this stage was his Discours préliminaire, the introduction to the encyclopedia that set the work’s rationalistic tone and methodology.

As in his other writings, he rejected the application of scientific methodology to metaphysical discussions. In doing so, he denied certain aspects of Cartesian methodology that were still widely accepted throughout France, and embraced the controversial Newtonian approach to scientific inquiry. Specifically, d’Alembert preferred to analyze problems that could be broken down into simpler components and then reconstructed into the whole. Since he was interested in limiting purely scientific discussion to what could be objectively measured or observed, he tended to avoid metaphysical and theological arguments that depended heavily on speculation rather than demonstrable facts.

The Discours brought d’Alembert to Voltaire’s attention as a major new force in philosophy. As their friendship developed, Voltaire convinced d’Alembert to write an article on Geneva for the Encyclopédie. Unfortunately, Voltaire’s information about the city’s relatively liberal Protestantism was incomplete, and d’Alembert compared the city’s religious leaders to freethinking Socinians.

After the uproar over the Geneva article, d’Alembert began to withdraw from work on the Encyclopédie. Since he wished to remain in Paris, he prudently chose to be less combative than some of his exiled peers. Though he remained loyal to the philosophe cause, he was not especially interested in some of the power-seeking aspects of their lifestyle. Despite an underlying interest in issues surrounding free thinking, d’Alembert avoided becoming involved in affairs that would not only risk exile, but also divert his attention away from scientific and mathematical interests. Because of the increasing pressures and distractions surrounding the Encyclopédie, he stepped down as editor in 1758, but continued to contribute articles.

Nonetheless, d’Alembert was still closely tied to the philosophes. The difficulty of his election to the French Academy indicated a continuing but faltering resistance to the philosopher caucus. Despite support from Montesquieu, Charles Louis de Secondat, Baron de as early as 1751 on the strength of the Discours préliminaire, d’Alembert did not join the Immortals until his fourth nomination in 1754. In keeping with his philosophical approach to the Academy, d’Alembert began to push for the elimination of censorship of Academic writings by the Sorbonne faculty. Though this stance put him at odds with Duclos, the Permanent Secretary, d’Alembert exhibited a desire to make the Academy more independent from court or church caprices. He rose to the Permanent Secretary post in 1772. While he carried on old projects like the Histoire de l’Académie, he continued to press for more autonomy for the institution as well as more public accountability.

While work on Diderot’s Encyclopédie and later in the French Academy brought d’Alembert public recognition, it was through his earlier success as a scientist and mathematician that he gained recognition outside of France. Shortly after his election to the Berlin Academy of Sciences, he expanded on his Réflexions sur la cause générale des vents with La Théorie générale des vents, which he dedicated to King Frederick II of Prussia. This gesture helped to begin a lifelong friendship between the mathematician and Prussia's Philosopher King, which was further cemented by their mutual friendship with Voltaire.

Although d’Alembert and Frederick II were very close, the king was not able to convince the philosopher mathematician to accept the post of Permanent Secretary of the Berlin Academy of Sciences. Despite the occasional difficulty of being a well known philosophe in Paris, d’Alembert had no desire to leave France for any extended period. He did agree, however, to help Frederick II find suitable candidates to fill various scientific advisory positions. Similarly, d’Alembert became good friends with Catherine II, the Great of Russia, another monarch who was trying to apply philosophical principles to ruling a nation. Like Frederick II, the czarina wished to have d’Alembert join her royal court, but after turning down the king of Prussia, he could hardly accept a similar post in Russia. As with Frederick II, he agreed to assist Catherine II in selecting advisors.

In his later years, as before, d’Alembert continued to struggle for the philosophe cause in his writings and in the French Academy. Though his reluctance to engage in some of the more esoteric disputes surrounding theology prevented his achieving the lasting reputation of his friends Voltaire and Diderot, he did make significant contributions to the pursuit of knowledge and reason at the end of France’s Ancien Régime.

Further reading:

Ronald Grimsley, Jean D’Alembert (1717-83), 1963.

Véronique Le Ru, Jean Le Rond d'Alembert philosophe, 1994.

Steven Daniell