Our work has the aim to describe the process of interaction in the eighteenth century epistolary through the study of three examples of epistolary dialogues, namely: Voltaire ---- Madame du Deffand, Rousseau and Malesherbes ---- finally Benjamin Constant ---- Isabelle de Charrière. We understand the interaction epistolary the back-and-forth between the two parties, their mutual influence, their trade roles. The main question thatarises here is: what is the interest for the two parties, this epistolary exchange in the long term? For what purpose is the two letter writers they write to each other? How epistolary dialogue can it change the image of the other, the structure and the moral?The eighteenth century saw a proliferation epistolary actually thanks to the development of philosophicalthought and the Enlightenment. It tasted like the epistolary exchange that affects all areas of life, especially among friends. So many businesses are built correspondence, some of which develop into networks. For Voltaire and Madame Du Deffand their epistolary follows a binary rhythm, usually smooth, but sometimes"syncopated" as a philosophical dialogue dazzling until the disappearance of Voltaire. In this dialogue, w ediscover the days many ideas and themes that inform us about a time excellently. Correspondence of Rousseau and Malesherbes us about minute details related to the problems of publication and censorshipworks, not to mention the personal side of their friendship, but is rather based on a kind of desire loyalty and commitment vision in the exchange of secrets, essential characteristics denominations which Rousseau has accustomed us. As Benjamin Constant and Isabelle de Charrière, their dialogue, despite the age difference between partners, seems very interesting content. If Constant likes to describe Isabelle de Charrière the circumstances of his life in a subsidiary, an interest, a passion sustained emerges in this correspondence.
