Invited public talk, concluding the afternoon session of the ‘Nacht van Descartes’ of the University of Utrecht, Descartes Centre for the History of the Natural Sciences and Humanities, 2 October 2008. Full title Descartes agonistes: The ‘Real’ Descartes Stands Up–How the agendas, identities, rebellions, successes, failures and delusions of ‘youth’ (1618-33) generated the historians’ mature Descartes.