As the act of writing is eminently dramatic, implying an unfolding or splitting of the subject, that constitutes the degree zero of every fiction, the epistolary discourse, as writing of the I, tends to create an interval towards «feigning» (fingimento). That is where we can spot its proximity with the literary sphere, operating also in the passage from the private to the public or in the intrusion of a reader unknown to both correspondents. That is why the letter, which is an ambiguous, hybrid and multifunctional form, is the source of different readings and misunderstandings, creating the illusion of being a place of maximum sincerity and an historic document which one could use for autobiographical data. This essay attempts to demonstrate how Fernando Pessoa’s correspondence is defined by a permanent tension between «truth» and «non-truth» and, thus, cannot be read without proper caution, without a necessary contextualization and appropriate research.