Paride ed Elena, the last of Gluck and Calzabigi’s three reform operas, is studied as a response to Rousseau’s juxtaposition of Italian and French music in the Lettre sur la musique françoise, and of French classical drama and Genevan public festivals in the Lettre à d’Alembert. On the one hand, the opera’s depiction of the cross-cultural love of the Trojan prince and the Spartan queen emerges as a rejection of Rousseau’s depreciation of French music and drama, along with his idealisation of Italian music and Genevan culture. On the other hand, as a theatrical reimagining of Rousseau’s novel Julie, ou La Nouvelle Héloïse, it suggests how he himself transcended these hard-edged dichotomies, paving the way for a new musical-theatrical language.