In 1767-1768 Voltaire wrote multiple times to the French authorities, whether to persuade them to improve living conditions in the Pays de Gex or to defend his own reputation as a royal historian. He also published plays, short stories and essays on topics as diverse as economics, religious tolerance and literary criticism. His fantasy "La Princesse de Babylone" was widely successful, both as a highly comic tale and an expression of Enlightenment values. Voltaire also turned his hand to comic opera in "Les Deux Tonneaux" and "Le Baron d'Otrante", as well as displaying his now familiar dexterity in verse fable and tragedy. His play "Les Guebres" as a theatrical reworking of the arguments of the "Traite sur la tolerance", which condemned establishment anti-Protestantism, through the story of the persecution of a minority religion under the Roman Empire. Voltaire's work on economic theory displays both his debt to the prevailing views of his time and his independence from them, in regarding human welfare, rather than national power, as the goal of economic activity. In some respects, 1768 can be regarded as a year of relative optimism for Voltaire, in the belief that the philosophic cause was gaining ground.