This volume includes six essays, the first dating from 1935 and the last from 1967, by one of the outstanding economists of our time. The economics presented in this volume is political economy worthy of the name: a discipline which shows us the social relations, in particular the class and group conflicts, behind the economic quantitative relations. Michal Kalecki, as Joan Robinson has pointed out, anticipated the Keynesian system, from a training in the field of Marxist economics. The translation to English was executed by the author himself, just before his death in April 1970.