Les Presses Universitaires de France and Frémeaux & Associés offer this biography of Diogenes, analyzed and explained by Jean-Manuel Roubineau, lecturer in ancient history and specialist in social history and the history of ancient sport. An atypical philosopher, Diogenes did not forbid any extravagance, did not submit to any of the social conventions in force in the Greece of his time, the 4th century BC. But if Diogenes has remained, until today, a familiar figure in Western culture, it is first and foremost because of his role in the birth of a major philosophical current: the cynicism. Passed successively through all conditions - citizen, foreigner, slave, freed - Diogenes displays his detachment with regard to social and political affiliations, until he declares himself a citizen of the world and, at the same time, inventing cosmopolitanism. Jean-Manuel Roubineau retraces Diogenes' journey in a clear and lively way and allows us to grasp the complexity of the philosopher.