He formed new musical projects, and he was introduced by degrees to many people of rank and influence, among them Madame d'Epinay (q.v.), to whom in 1747 he was introduced by her lover M.
Shortly afterwards, returning to Paris, he accepted a cottage near Montmorency (the celebrated Hermitage) which Madame d'Epinay had fitted up for him, and established himself there in April 1756.
Here he wrote La Nouvelle Heloise; here he indulged in the passion which that novel partly represents, his love for Madame d'Huodetot, sister-in-law of Madame d'Epinay, a lady young and amiable, but plain, who had a husband and a lover (St Lambert), and whom Rousseau's devotion seems to have partly pleased and partly annoyed.
The quarrel with Madame d'Epinay, with Diderot, and through them with the philosophe party reversed this.
There is little doubt that for the last ten or fifteen years of his life, if, not from the time of his quarrel with Diderot and Madame d'Epinay, Rousseau was not wholly sane - the combined influence of late and unexpected literary fame and of constant solitude and discomfort acting upon his excitable temperament so as to overthrow the balance, never very stable, of his fine and acute but unrobust intellect.
D'Epinay and others, and while Mrs Macdonald's researches have done much to suggest a rehabilitation of Rousseau's veracity they have not definitely been accepted to an extent which would justify the rewriting of these other lives in her sense.
D'Epinay, Renseignements pour servir a l'histoire de ale de France jusqu'd r8ro (Mauritius, 1890); N.