While the studies of D'Alembert were confined to geometry, he was little known or celebrated in his native country. His connections were limited to a small society of select friends; he had never seen any man in high office except the Marquis d'Argenson. Satisfied with an income which furnished him with the necessaries of life, he did not aspire after opulence or honours; nor had they been hitherto bestowed upon him, as it is easier to confer them on those who solicit them than to look out for men who deserve them. His cheerful conversation, his smart and lively sallies, a happy knack at telling a story, a singular mixture of malice of speech with goodness of heart, and of delicacy of wit with simplicity of manners, rendered him a pleasing and interesting companion; and his company, consequently, was much sought after in the fashionable circles. His reputation at length made its way to the throne, and rendered him the object of royal attention and beneficence. He received also in 1756 a pension from Government, which he owed to the friendship of M. d'Argenson.
D'Alembert's association with Diderot in the preparation of the celebrated Dictionnaire Encyclopédique led him to take a somewhat wider range than that to which he had hitherto confined himself. He wrote for that work the Discours préliminaire on the rise, progress, and affinities of the various sciences, which he read to the French Academy on the day of his admission as a member, the 19th December 1754. Condorcet, in his Éloge, characterizes it as one of those works which only two or three men in a century could produce. Comprehensive in its plan, and clear in its statement, it deserves this often quoted praise; but it is open to the criticism that the fundamental principle, adopted from Bacon, on which it classifies the sciences is untenable. D'Alembert distinguishes the human faculties into memory, reason, and imagination, and following out that distinction classifies all science under the three heads of history or the science of memory, philosophy or the science of reason, and poetry or the science of imagination. Now, it is obvious that even if these are in each case the faculties primarily concerned, which is not beyond question, no science is the product of any one faculty exclusively. D'Alembert wrote several literary articles for the first two volumes of the Encyclopædia, after which the work was suppressed for a time. To the remaining volumes he contributed mathematical articles chiefly. One of the few exceptions was the article on “Geneva,” which involved him in a somewhat keen controversy in regard to Calvinism and the suppression of theatrical performances within the town. During the time he was engaged on the Encyclopædia he wrote a number of literary and philosophical works, which extended his reputation and also exposed him to criticism and controversy, as in the case of his Mélanges de Philosophie, d'Histoire, et de Littérature. His Essai sur la société des gens de lettres avec les grands was a worthy vindication of the independence of literary men, and a thorough exposure of the evils of the system of patronage. He broke new ground and showed great skill as a translator in his Traduction de quelques morceaux choisis de Tacite. One of his most important works was the Éléments de Philosophie, published in 1759, in which he discussed the principles and methods of the different sciences. He maintained that the laws of motion were necessary, not contingent. The work furnished occasion for a renewal of his correspondence with Frederick the Great. A treatise Sur la destruction des Jésuites (1765) involved him in a fresh controversy, his own share in which was rendered very easy by the violence and extravagance of his adversaries. The list of his more noteworthy literary works is completed by the mention of the Histoire des membres de l'Académie française, containing biographical notices of all the members of the Academy who died between 1700 and 1772, the year in which he himself became secretary. D'Alembert was much interested in music both as a science and as an art, and wrote Éléments de Musique théorique et pratique, which was based upon the system of Rameau with important modifications and differences.
D'Alembert's fame spread rapidly throughout Europe and procured for him more than one opportunity of quitting the comparative retirement in which he lived in Paris for more lucrative and prominent positions. The offer of Frederick the Great has already been mentioned. In 1762 he was invited by Catherine of Russia to become tutor to her son at a yearly salary of 100,000 francs. On his refusal, the offer was repeated with the additional inducement of accommodation for as many of his friends as he chose to bring with him to the Russian capital. D'Alembert persisted in his declinature, and the letter of Catharine was ordered to be engrossed in the minutes of the French Academy. A foreign honour of a different kind had previously been bestowed upon him. In 1755, on the recommendation of Pope Benedict XIV., he was admitted a member of the Institute of Bologna. A legacy of £200 from David Hume showed the esteem in which he was held by that philosopher.
