In 1749 Diderot was a prisoner at Vincennes. Rousseau, on the road to visit his friend, read in the _Mercure de France_ that the Academy of Dijon had proposed as the subject for a prize to be awarded next year the question, "Has the progress of arts and sciences contributed to purify morals?" Suddenly a tumult of ideas arose in his brain and overwhelmed him; it was an ecstasy of the intellect and the passions. With Diderot's encouragement he undertook his indictment of civilisation; in 1750 the _Discours sur les Sciences et les Arts_ was crowned. In accordance with his theory he proceeded to simplify his own life, intensifying his self-consciousness by singularities of assumed austerity, and playing the part (not wholly a fictitious one) of a moral reformer. Famous as author of the _Discours_ and the opera _Le Devin de Village_, presented before the King, he returned to his native Switzerland, and there re-entered the Protestant communion. In 1754 he again competed for a prize at Dijon, on the question, "What is the origin of inequality among men, and is it authorised by the law of nature?" Rousseau failed to obtain the prize, but the _Discours sur l'Inegalite_ was published (1755) with a dedication to the Republic of Geneva. He had discovered in private property the source of all the evils of society. In Switzerland Rousseau prepared a first redaction of his political treatise, the _Contrat Social_, and filled his heart with the beauty of those prospects which form an environment for the lovers in his Heloise. In 1756 he was established, through the kindness of Madame d'Epinay, in the Hermitage, near the borders of the forest of Montmorency. His delight in the woods and fields was great; his delight in Madame d'Houdetot, kinswoman of his hostess, was a more troubled passion. Quarrels with Madame d'Epinay, quarrels with Grimm and Diderot, estrangement from Madame d'Houdetot, closed the scene at the Hermitage.