Frederick II. gave D’Alembert a pension; it had but lately been Louis XIV. who thus lavished kindnesses on foreign scholars:  he made an offer to the Encyclopaedists to go and finish their vast undertaking at Berlin.  Catherine II. made the same offers, asking D’Alembert, besides, to take charge of the education of her son.  “I know your honesty too well,” she wrote, “to attribute your refusals to vanity; I know that the cause is merely love of repose in order to cultivate literature and friendship.  But what is to prevent your coming with all your friends?  I promise you and them too all the comforts and every facility that may depend upon me; and perchance you will find more freedom and repose than you have at home.  You do not yield to the entreaties of the King of Prussia, and to the gratitude you owe him, it is true, but then he has no son.  I confess that I have my son’s education so much at heart, and that you are so necessary to me, that perhaps I press you too much.  Pardon my indiscretion for the reason’s sake, and rest assured that it is esteem which has made me so selfish.”

D’Alembert declined the education of the hereditary Grand Duke, just as he had declined the presidency of the Academy at Berlin; an infidel and almost a materialist by the geometer’s rule, who knows no power but the laws of mathematics, he did not carry into anti-religious strife the bitterness of Voltaire, or the violence of Diderot.  “Squelch the thing! you are always repeating to me,” he said to Voltaire on the 4th of May, 1762.  “Ah! my good friend, let it go to rack and ruin of itself, it is hurrying thereto faster than you suppose.”  More and more absorbed by pure science, which he never neglected save for the French Academy, whose perpetual secretary he had become, D’Alembert left to Diderot alone the care of continuing the Encyclopaedia.  When he died, in 1783, at fifty-six years of age, the work had been finished nearly twenty years.  In spite of the bad faith of publishers, who mutilated articles to render them acceptable, in spite of the condemnation of the clergy and the severities of the council, the last volumes of the Encyclopaedia had appeared in 1765.

This immense work, unequal and confused as it was, a medley of various and often ill-assorted elements, undertaken for and directed to the fixed end of an aggressive emancipation of thought, had not sufficed to absorb the energy and powers of Diderot.  “I am awaiting with impatience the reflections of Pantophile Diderot on Tancrede,” wrote Voltaire:  “everything is within the sphere of activity of his genius:  he passes from the heights of metaphysics to the weaver’s trade, and thence he comes to the stage.”

The stage, indeed, occupied largely the attention of Diderot, who sought to introduce reforms, the fruit of his own thought as well as of imitation of the Germans, which he had not perhaps sufficiently considered.  For the classic tragedies, the heritage of which Voltaire received from the hands of Racine, Diderot aspired to substitute the natural drama.  His two attempts in that style, Le Pere de Famille and Le Fils natural, had but little success in France, and contributed to develop in Germany the school already founded by Lessing.  An excess of false sensibility and an inflation of expression had caused certain true ideas to fall flat on the French stage.