Despite a century of debate and criticism, Marxism as a mass ideological practice has remained an elusive topic. This book examines Marxist socialism as a mode of understanding and self-understanding treasured and transmitted by thousands of anonymous militants. It focuses on the Parti Ouvrier Francais, the Guesdists, an archetypal movement of Marxism's Golden Age before World War I, the period when Marxist socialism evolved from sect to mass movement...