This article addresses the issue of how the market and the non-market are to be understood especially by concentrating on the theory of money. For mainstream economics, the market is simply an institution facilitating exchange, money being the key instrument for alleviating the inefficiencies of barter. In contrast, recent work in other social sciences, such as that by Zelizer, distinguishes among markets, and various roles of money, depending on cultural and social content. While being sympathetic to such an approach, we claim that the commodity is a better analytical starting point than the market. Based on Marx's work, we then show what commodities have in common and establish a common essence for money as generalized purchasing power. This is a peculiarly bland essence that allows money to undertake the variety of social roles identified by Zelizer.