The rise to dominance of marginalist economics coincided with a major increase in the spread of socialist ideas. As many socialist and Marxist thinkers were preoccupied with economic questions this was scarcely a development they could ignore. Socialists either had to defend Marxist economics against marginalist criticism or show that socialism and marginalism were compatible.This volume explores the varied socialist responses in a number of major European countries including Italy, France, Russia and the German-speaking countries. No one response prevailed: some socialists defended Marxist economics and rejected marginalism; others criticized Marxist economics 'from within' without adopting marginalism to any significant degree. Yet others sought to effect a theoretical compromise or amalgam, or, again, to advocate an outright acceptance of marginalist economics and its use in arguing for socialism. The first chapter presents the general findings on a 'cross-country' basis, while the remaining eight chapters provide detailed case studies.The relations between marginalism and socialism are shown to be highly complex and variable, and this book pays equal attention to the differences and the common themes. It also highlights some of the many, innovative contributions to 'classical' political economy, some of which were only to be rediscovered after many decades.