This article sheds new light on Jean Genet's complex notion of political commitment. It does so by focusing on a biographical event, which has been hitherto underestimated by critics: namely, his traumatic encounter with an abject travelling companion in a third-class railway carriage in the early 1950s. This painful experience, defined as 'la blessure' or wound, gets to the core of Genet's politics, for it determines his ethical understanding of commitment, which, like Emmanuel Levinas's alternative concept of humanism, is grounded in alterity, respecting the difference of the Other. Additionally, the wound illuminates other little-discussed aspects of Genet's politics, including his anarchic, deterritorialized view of le champs politique and his curious decision to define himself as a witness in his final work, "Un captif amoureux" (1986).