In the framework of a critical illustration of the contemporary history of economics, this chapter provides an illustration of Sraffa’s thought, from his first writings on money and banking to his book on “Production of commodities by means of commodities”. His friendship with and cultural relations with Gramsci, Wittgenstein, Keynes are considered, as well as his critique of Marshall’s theory of the firm and the notion of the representative firm. His proposal of a theory of imperfect competition and the reasons for its abandonment are illustrated. The role of the critical edition of Ricardo’s writings for the reconstruction of the Classical approach is stressed. An interpretation is provided for Sraffa’s contribution to the Classical theory of prices and distribution and for his critique to the marginalist approach.