A physicist and Ingénieur des Mines, Geismar became a university teacher in Paris in 1963 and general secretary of the higher education teachers’ union (SNESup) in 1967. He was catapulted to notoriety as one of the triumvirate (alongside Daniel Cohn-Bendit and Jacques Sauvageot) who acted as leaders and spokespersons for the May 1968 student movement. His ‘Maoist’ political affiliations in the immediate post-1968 years seem to have had no adverse effect on his subsequent career. He was an official in the Département d’Education Permanente (1974-8) and vicepresident of the University of Paris VII (19824). In 1985, he became assistant director-general of the Agence de l’Informatique and later acted as an adviser to Jack Lang, when he was Minister of Culture.