The purpose of this paper is, by analyzing Guilleragues’ Lettres portugaises under the theme of epistolary madness, to decide their structure and their place in the history of literature. First, the research history shows that the madness has been a main issue of the interpretation, and that its understanding is a matter of determining the mode of narration between monologue and dialogue.
Leo Spitzer’s study is the starting point, because it observes the transition from dialogue to monologue and the meaning of this transition which is a restoration of reason. However, our analysis demonstrates that the Lettres are composed of a succession of madness, and that each madness expresses a specific epistolary logic. Therefore, the Lettres must be regarded as an important moment in the history of the genre of epistolary novels, in that they investigate the modern subjectivity in connection with the characteristics of the letter as medium.