ALEMBERT, JEAN LE ROND D' (1717–1783)

ALEMBERT, JEAN LE ROND D' (1717–1783), French mathematician, scientist, philosopher, and writer. Born 17 November 1717, Jean Le Rond d'Alembert was the illegitimate son of the famous Claudine Alexandrine Guérin, marquise de Tencin, and an artillery officer, Louis-Camus Destouches. Abandoned on the steps of Saint-Jean-Le-Rond in Paris, he was taken to the Foundling Home and named after the church where he was discovered. Through his father's efforts he was placed with a foster mother, Mme. Rousseau, to whom he remained devoted. His father also saw to it that his son received a good education; he attended first a private school, then the Collège des Quatre-Nations. After three years studying law and medicine, it became clear to d'Alembert that mathematics was his true vocation. In 1741 he was named an adjoint (adjunct) at the Academy of Sciences, and in 1743 he published his most important mathematical work, the Traité de dynamique (Treatise on dynamics). In addition to six other major scientific treatises, his 1752 Éléments de musique, théorique et pratique, suivant les principes de Rameau (Elements of practical and theoretical music following Rameau's principles) is noteworthy as a lucid exposition of Rameau's hugely influential harmonic theory.

Today d'Alembert is somewhat undervalued, remembered mostly as coeditor of the Encyclopédie, although even in that enterprise he was eclipsed by Denis Diderot (1713–1784). In his day d'Alembert was esteemed second only to Voltaire (1694–1778) in leading the philosophe movement, the very core of Enlightenment ideology. Through his role in the French Academy, to which he was elected in 1754, and of which he became permanent secretary in 1772, the discreet and cautious d'Alembert was able to confer legitimacy on many of the philosophes' deepest concerns while remaining immune to the imprisonments and exiles that punctuated the lives of so many of his colleagues.

Largely because of his scientific reputation, but also because he was a popular, brilliant participant in Parisian salons, d'Alembert was asked as early as 1745 to participate in the production of the Encyclopédie; in 1747 he was named coeditor with Diderot and was charged primarily with the mathematical and scientific articles. His nonscientific entry, the infamous "Genève," created a controversy with Jean-Jacques Rousseau (1712–1778) and then with Genevan Protestants, leading d'Alembert to resign from his editorial post in 1758.

The desire to avoid scandal at all costs, which led to his resignation, was consistent with the public comportment d'Alembert adopted for the rest of his career. Although he shared many of the goals of the other philosophes, his correspondence (in particular with Voltaire) consistently shows not only a refusal to jeopardize his career and freedom to remain in Paris but also an unflinching conviction that enlightenment must be a gradual and tactful process of persuasion rather than a series of attacks, whether open or anonymous. He thought he could best serve that end by promoting the philosophe party at large and especially in the Academy, by mediating disputes within the group and by functioning as a de facto public relations manager as a foil to the polemical outpourings from Voltaire at Ferney and from numerous other quarters (most notably the baron Paul Thiry, baron d'Holbach; 1723–1789). Indeed, it had long been Voltaire's wish that when he died, d'Alembert would succeed him as leader of the philosophes. Much of d'Alembert's immense stature in the eighteenth century, then, came not from his writings but from his ceaseless efforts to unite and promote his colleagues and advance their mutual cause.

In 1759 he laid out his philosophical principles and methodology in his Essai sur les éléments de philosophie: ou sur les principes des connaissances humaines (Essay on the elements of philosophy, or on the principles of human knowledge). In this work he provides a synthesis of his prior thought in epistemology, metaphysics, language theory, science, and aesthetics. The Éclaircissements (Explanations), added in 1767, round out the Essay, forming a composite that represents the ambitious scope of d'Alembert's empiricist philosophy.

However, his most important work is without doubt the 1751 Preliminary Discourse to the Encyclopedia. In this concise and occasionally flawed but often brilliant document, d'Alembert seeks to justify the encyclopedic enterprise in a Lockean vein, by showing the unity of all thought from its sensorial origins (in "direct" and "reflected" ideas deriving from corporeal impressions). However, he also attempts to provide a rational, scientific method for the mapping of human knowledge as well as a historical account of the evolution of human thought. The result is not merely an apology for the ends as well as the means of the Encyclopédie, it is also a superb summation of Enlightenment empirical and sensualist thought, a forceful rejection of Cartesian metaphysics (if not Cartesian method, which d'Alembert admired), and a valorization of the scientific method of Francis Bacon (1561–1626) and (particularly) Isaac Newton (1642–1727). In the Discourse, d'Alembert succeeds in showing the intimate connection between the spirit of the Encyclopédie and the concerns of the Enlightenment generally, in a way that is not always obvious to the reader of the encyclopedia's articles themselves.

D'Alembert's last important work, the fifth volume of Mélanges de littérature, d'histoire, et de philosophie, was published in 1767. From that point on, his health became increasingly fragile. In his last years he wrote little, instead concentrating on his duties as permanent secretary of the French Academy. As the result of his refusal of an operation (without which his doctors informed him he would not survive) for a painful bladder ailment he had had for years, d'Alembert died on 29 October 1783.

ALEMBERT, JEAN LE ROND D' (1717–1783)

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