What are the founding principles of anarchism? What links the philosophy of Proudhon, who introduced this notion in France in 1840, to the act of the Italian Sante Geronimo Caserio, who assassinated President Sadi Carnot in 1894? This introduction to anarchism helps us understand the issues and tensions that run through this movement, and to grasp why it could establish itself today as a response to the moral and economic crisis of contemporary societies.