Is Julie ou la Nouvelle Héloïse simply « a voluptuous dream rectified as a moral lesson? » Common to the two lovers’ initial passion and to M. and Mme de Wolmar’s marriage is that both must include a third party. Claire is ‘inseparable’ from the the lovers and to the Wolmar couple Saint-Preux seems no less necessary. Rousseau sketches out the experience of three people living as a couple, which is developed in terms of marriage and alternation by Saint-Lambert in Les Deux Amis, and then of eroticism and simultaneity by Casanova in the Histoire de ma vie. Rousseau can be reread through the prism of Fourier and the amorous utopias of May ’68 that continue to feed contemporary cinematic fictions.