Gustav Landauer's letters are part of the letter writing culture of the late 19th century. He exchanged letters with Wilhelm Bölsche, Else Lasker-Schüler, Martin Buber, Erich Mühsam, Fritz Mauthner, Hugo von Hofmannsthal and Petr Kropotkin. The letter as a medium of bourgeois "conversation culture" not only serves as a lifeline but also as a highly productive tool for the interpreter, journalist, dramatic adviser and political thinker that he was. These highly treasured personal testimonies are comprehensive witnesses of the German-Jewish letter writing culture, which influenced both the oppositional circles of the German Empire as well as the aesthetic and philosophical modern times.