On 20 May 1961 Foucault defended his two doctoral theses; on 2 December 1970 he gave his inaugural lecture at the Collège de France. Between these dates, he published four books, travelled widely, and wrote extensively on literature, the visual arts, linguistics, and philosophy. He taught both psychology and philosophy, beginning his explorations of the question of sexuality. Weaving together analyses of published and unpublished material, this is a comprehensive study of this crucial period. As well as Foucault's major texts, it discusses his travels to Brazil, Japan, and the USA, his time in Tunisia, and his editorial work for Critique and the complete works of Nietzsche and Bataille. It was in this period that Foucault developed the historical-philosophical approach he called 'archaeology' - the elaboration of the archive - which he understood as the rules that make possible specific claims. In its detailed study of Foucault's archive the book is itself an archaeology of Foucault in another sense, both excavation and reconstruction. This book completes a four-volume series of major intellectual histories of Foucault. Foucault's Last Decade was published by Polity in 2016; Foucault: The Birth of Power followed in 2017; and The Early Foucault in 2021.