In the unpublished manuscript of a lecture course probably given by Foucault at the École normale supérieure of Paris in 1954–5 (‘On Anthropology’; the dating is still uncertain), Foucault undertakes an erudite and detailed reconstruction of the history of anthropological knowledge, from modernity (Descartes and Malebranche) to 20th-century Nietzschean commentaries (Jaspers and Heidegger), including analyses by Kant, Feuerbach, and Dilthey, among others. My article explores this lecture course to emphasize the importance of anthropological criticism for the young Foucault, addressing in particular the anti-anthropological significance of the encounter with Nietzsche’s philosophy, which becomes an output power ( puissance de sortie) both of the figure of man and the notion of truth in which he was involved. These unpublished manuscripts will therefore allow me to find a common thread in Foucault’s work in the 1950s and 1960s (and even beyond): the exploration of new potentialities for thought opened by ‘the death of man’.