The concept of reproduction -- Adam Smith and the concept of natural price -- David Ricardo and the labor theory of natural price -- Marx's theory of exploitation and surplus value -- Marx's theory of natural price -- Balanced growth and the conservation of surplus value -- Envoi : some doubts about Marx's theory of value and exploitation -- Appendix A. A formal analysis of Ricardian and Marxian political economy -- Appendix B. An analytical reconstruction of Marx's value categories.