This paper is based on the archives of Michel Foucault collected (since 2013) at the manuscripts department of the Bibliothèque nationale de France, Paris. Our investigation focuses in particular on the documents of the 1950s, in order to study the role of the reflection on anthropology and phenomenology at the beginning of Foucault’s philosophical path. This archival material allows us to discover the tremendous work that is at the basis of the relatively few works that Foucault published in the 1950s. The access to the 1950s documents enables us at last to investigate the reasons for the seemingly sharp break that divides these works from the works published by Foucault in the 1960s and the 1970s, in which emerges the archaeological refusal of phenomenology and anthropology, as well as the strong criticism against any form of psychopathological discourse.