Plato presented him as a "mad Socrates" (a Socrates who has gone mad). The eccentricities of his behavior and his outspokenness made him a legend. Diogenes, an unconventional philosopher with a tendency to exceed boundaries, did not submit to any social norm, and if he remained from the 4th century BC as a form of Western civilization, it is primarily for his role in the creation of a great philosophical movement, Cynicism. A follower of a "philosophy in action," he chose to live as a beggar, advocated a return to Nature, and constantly denounced the deceptive tricks that are given and taken in social relationships.

Jean-Manuel Rubino designs the portrait of this thinker with a thousand lives: successively a citizen of Sinope, a foreigner in exile in Athens, a slave enslaved by pirates, and then liberated. He illuminates the journey of a human character of radical uniqueness, who, refusing to belong anywhere, declared himself a citizen of the world and invented a new ideal: cosmopolitanism.