Judith Dellheim is a senior research fellow at the Rosa Luxemburg Foundation, Berlin, Germany. She has worked in the foreign trade of the GDR. Since 1990, she has been working on economies of solidarity, on political parties and movements, and on economic policies. She has been a member of the Federal Board of the PDS in 1995–2003, a free-lance scientific consultant from 2004–2010, and senior researcher at the Rosa Luxemburg Foundation since 2011. She is co-author of Rosa Luxemburg: A Permanent Challenge for Political Economy. Frieder Otto Wolf is Honorary Professor of Philosophy at the Free University of Berlin, Germany. He has been a lecturer in philosophy at this institution since 1973, and became Honorary Professor in 2007. He has served as a fellow at the Rosa Luxemburg Foundation and sits on the advisory board of several journals. He has published books and articles on political philosophy, the politics of labor, the politics of sustainability, political epistemology, and metaphilosophy, including as co-author of Rosa Luxemburg: A Permanent Challenge for Political Economy.