Qu’est-ce que fonder? was the title of a "cours hypokhâgne" that Deleuze gave at the Lycée Louis le Grand in Paris during the 1956-1957 academic year. The hypokhâgne is the first year course, followed by khâgne, of the two-year academic cycle in France (Classe préparatoire aux grandes écoles) whose aim is to prepare high school students for the entrance competition of the École normale supérieure in Paris. The text is based on the notes of one of the students in the course, Pierre Lefebvre.
An English translation of the course, entitled What is Grounding?, translated by Arjen Kleinherenbrink and edited by Tony Yanick, Jason Adams, and Mohammad Salemy, is available online at the webpage for The New Centre for Research and Practice, tripleampersand.org/books.