Gustav Landauer invokes a "social psychology" whose content is a radical critique of the society of his time. At the beginning, Landauer was an independent socialist as well as a social democrat, but his ideological positions gradually changed towards anarchism. This itinerary, at the same time biographical and political, reflects great events of his time, from the congresses of the Second International, in which the separation between social democracy and anarchism matures, to the Republic of the Bavarian Councils, where the May 2, 1919, murdered in prison by a group of police officers who were never convicted for it. Despite the dramatic times in which he lives, Landauer is firmly convinced that another world is not only necessary, but also possible, here and now; therefore, the validity of his work. In addition, this edition has a new prologue written by José María Ripalda.