At twelve years, Jean the Round of Alembert enters to the college of the Four-Nations. It is a college founded by Mazarin and held by religious Jansenists and Cartesian. D' Alembert is pointed out by its professors thanks to its gifts for the old languages and philosophy. He studies then the right while devoting his leisures to mathematics. Lawyer in 1738, it starts to study medicine before devoting itself definitively to mathematics. Its first work, in particular a report on the refraction of the solid bodies, is noticed, and, at twenty-four years, it enters to the Academy of Science like “associated assistant astronomer”.

Its scientific work
The scientific work of Alembert relates primarily to mechanics. In 1743, it publishes a Treaty of dynamics which ensures its dedication. It is in this treaty that it states the general theorem of dynamics known since under the name of “principle of Alembert”. The following year, it publishes a Treaty of balance and movement of the fluids which bases the hydrodynamics on the principles of dynamics.  

In 1746, it gains a contest with the Academy of Berlin for a treaty on the atmospheric tides and is concentrated then on the problem of the vibrating cords, study at the time of which it gives the first example of an equation of wave.

In 1749 its Research appears on the precession of the equinoxes and the change of the Earth in the Newtonian system, which are remarkable applications of the theorem of dynamics.  

In mathematics, it gives, in 1746, a demonstration of the fundamental theorem of the algebra (“any nonconstant polynomial with complex coefficients admits at least a complex root”). This demonstration is not complete and will be taken again per Gauss.

Lights
Equipped with an immense culture, it publishes also works on the music and translated Tacite. He attends the Parisian living rooms, in particular those of Mrs. of Deffand then of Julie de Lespinasse, and takes an active part very in the ideological debate of his time. Friend of Voltaire, of Alembert corresponds with the “enlightened monarchs” Catherine of Russia and Frederic of Prussia. Judging improper to be the hierarchically superior of Euler, for whom it has a very great admiration, it refuses to direct the Academy of Berlin. He refuses also the offer of Catherine of Russia to be the tutor of his son.

Its collaboration with Denis Diderot for the drafting of 28 volumes of the Encyclopedia starts in 1751. D' Alembert written most articles on mathematics which appears in it. It is him which is the author of famous preliminary Discours, considered like a genuine proclamation of the philosophy of the Lights. It writes also many philosophical articles in which it gives an opinion against the absolutism.

In 1759, of Alembert scrambles themselves with Diderot and resigns of the Encyclopedia. But it returns a few months later to devote itself only to the articles of mathematics and physics.

The publication of the Encyclopedia met a strong opposition of the Jesuits. In 1764, of Alembert publishes anonymously a lampoon, the Destruction of the Jesuits in France, and plays a big role in the expulsion of France about the Jesuits.

Elected official member of the French Academy in 1754, he becomes perpetual secretary in 1772 about it. He dies in full glory in 1783.