# Jean le Rond d'Alembert: Wikis

Note: Many of our articles have direct quotes from sources you can cite, within the Wikipedia article! This article doesn't yet, but we're working on it! See more info or our list of citable articles.

# Encyclopedia

Jean le Rond d'Alembert

Jean le Rond d'Alembert, pastel by Maurice Quentin de La Tour.
Born 16 November 1717
Paris
Died 29 October 1783 (aged 65)
Nationality French
Fields Mathematics
Mechanics
Physics
Philosophy
Known for Fluid mechanics
Encyclopédie

Jean le Rond d'Alembert (16 November 1717 – 29 October 1783) was a French mathematician, mechanician, physicist and philosopher. He was also co-editor with Denis Diderot of the Encyclopédie. D'Alembert's method for the wave equation is named after him.

## Childhood

Born in Paris, d'Alembert was the illegitimate child of the writer Claudine Guérin de Tencin and the chevalier Louis-Camus Destouches, an artillery officer. Destouches was abroad at the time of d'Alembert's birth, and a couple of days after birth his mother left him on the steps of the Saint-Jean-le-Rond de Paris church. According to custom, he was named after the patron saint of the church. D'Alembert was placed in an orphanage for found children, but was soon adopted by the wife of a glazier. Destouches secretly paid for the education of Jean le Rond, but did not want his parentage officially recognised.

Classical mechanics
$\mathbf{F} = \frac{\mathrm{d}}{\mathrm{d}t}(m \mathbf{v})$
Newton's Second Law
History of ...
Scientists
Isaac Newton · Jeremiah Horrocks · Leonhard Euler · Jean le Rond d'Alembert · Alexis Clairaut
Joseph Louis Lagrange · Pierre-Simon Laplace · William Rowan Hamilton · Siméon-Denis Poisson

D'Alembert first attended a private school. The chevalier Destouches left d'Alembert an annuity of 1200 livres on his death in 1726. Under the influence of the Destouches family, at the age of twelve D'Alembert entered the Jansenist Collège des Quatre-Nations (the institution was also known under the name "Collège Mazarin"). Here he studied philosophy, law, and the arts, graduating as bachelier in 1735. In his later life, D'Alembert scorned the Cartesian principles he had been taught by the Jansenists: "physical premotion, innate ideas and the vortices".

The Jansenists steered D'Alembert toward an ecclesiastical career, attempting to deter him from pursuits such as poetry and mathematics. Theology was, however, "rather unsubstantial fodder" for d'Alembert. He entered law school for two years, and was nominated avocat in 1738.

He was also interested in medicine and mathematics. Jean was first registered under the name Daremberg, but later changed it to d'Alembert. The name "d'Alembert" was proposed by Johann Heinrich Lambert for a suspected (but non-existent) moon of Venus.[citation needed]

## Career

In July 1739 he made his first contribution to the field of mathematics, pointing out the errors he had detected in L'analyse démontrée (published 1708 by Charles René Reynaud) in a communication addressed to the Académie des Sciences. At the time L'analyse démontrée was a standard work, which d'Alembert himself had used to study the foundations of mathematics. D'Alembert was also a Latin scholar of some note and worked in the latter part of his life on a superb translation of Tacitus, from which he received wide praise including that of Denis Diderot.

In 1740, he submitted his second scientific work from the field of fluid mechanics Mémoire sur la réfraction des corps solides, which was recognized by Clairaut. In this work d'Alembert theoretically explained refraction.

In 1741, after several failed attempts, d'Alembert was elected into the Académie des Sciences. He was later elected to the Berlin Academy in 1746 [1]

In 1743 he published his most famous work, Traite de dynamique, in which he developed his own laws of motion.[2]

When the Encyclopédie was organized in the late 1740s, d'Alembert was engaged as co-editor (for mathematics and science) with Diderot, and served until a series of crises temporarily interrupted the publication in 1757. He authored over a thousand articles for it, including the famous Preliminary Discourse. D'Alembert "abandoned the foundation of Materialism"[3] when he "doubted whether there exists outside us anything corresponding to what we suppose we see."[4] In this way, D'Alembert agreed with the Idealist Berkeley and anticipated the Transcendental idealism of Kant.

In 1752, he wrote about what is now called D'Alembert's paradox: that the drag on a body immersed in an inviscid, incompressible fluid is zero.

In 1754, d'Alembert was elected a member of the Académie française, of which he became Permanent Secretary on 9 April 1772.

## Personal life

D'Alembert was a participant in several Parisian salons, particularly those of Marie Thérèse Rodet Geoffrin, of the marquise du Deffand and of Julie de Lespinasse. d'Alembert became infatuated with Mlle de Lespinasse, and eventually took up residence with her.

## Death

He suffered bad health for many years and his death was as the result of a bladder illness. As a known unbeliever, D'Alembert was buried in a common unmarked grave.

## Legacy

In France, the fundamental theorem of algebra is known as the d'Alembert/Gauss theorem.

He also created his ratio test, a test to see if a series converges.

The D'Alembertian operator, which first arose in D'Alembert's analysis of vibrating strings, plays an important role in modern theoretical physics.

While he made great strides in mathematics and physics, d'Alembert is also famously known for incorrectly arguing in Croix ou Pile that the probability of a coin landing heads increased for every time that it came up tails. In gambling, the strategy of decreasing one's bet the more one wins and increasing one's bet the more one loses is therefore called the D'Alembert system, a type of martingale.

## Fictional portrayal

Diderot portrayed D'Alembert in "Le reve de D'Alembert" ("D'Alembert's Dream"), written after the two men became estranged. It depicts D'Alembert ill in bed, conducting a debate on materialist philosophy in his sleep.

The Andrew Crumey novel "D'Alembert's Principle" (1996) takes its title from D'Alembert's principle in physics. Its first part describes D'Alembert's life and his infatuation with Julie de Lespinasse.

## Bibliography

• Briggs, J. Morton (1970). "Jean le Rond d'Alembert". Dictionary of Scientific Biography. 1. New York: Charles Scribner's Sons. pp. 110–17. ISBN 0684101149.
• Crépel, Pierre, 2005, "Traité de dynamique" in Grattan-Guinness, I., ed., Landmark Writings in Western Mathematics. Elsevier: 159-67.
• Grimsley, Ronald (1963) Jean d'Alembert. Oxford Univ. Press.

## Notes

1. ^
2. ^ Pearsall, Judy; Trumble, Bill, Eds. (2001). The Oxford English Reference Dictionary. 2nd ed. Oxford University Press. ISBN 0-19-860046-1. p.32.
3. ^ Friedrich Albert Lange, History of Materialism and Critique of its Present Importance, "Kant and Materialism"
4. ^ Ibid.

 Preceded by Jean-Baptiste Surian Seat 25 Académie française 1754–1783 Succeeded by Marie-Gabriel-Florent-Auguste de Choiseul-Gouffier

# Quotes

Up to date as of January 14, 2010

### From Wikiquote

Jean le Rond d'Alembert () was a French mathematician, mechanician, physicist and philosopher. He was also co-editor with Denis Diderot of the Encyclopédie.

## Sourced

• Rien n'est plus incontestable que l'existence de nos sensations; ...
• Nothing is more incontestable than the existence of our sensations; ...

• D'Alembert was always surrounded by controversy. ... he was the lightning rod which drew sparks from all the foes of the philosophes. ... Unfortunately he carried this... pugnacity into his scientific research and once he had entered a controversy, he argued his cause with vigour and stubbornness. He closed his mind to the possibility that he might be wrong...
• Thomas L. Hankins (1990). Jean D'Alembert: Science and the Enlightenment. Taylor & Francis. p. 236. ISBN 2881243991.