This chapter develops a critique of certain approaches to markets and firm behaviour in economics and economic sociology. There are two main targets of the critique. The first concerns some common approaches to markets and the nature of firms in relation to them. The chapter argues that the diverse uses of the term 'market' in contemporary lay and academic discourse cause confusion. The second target of critique concerns literature on the socially embedded character of economic processes, on the nature of networks, and the role of trust. The chapter argues that their treatment has suffered frequently from being idealist, both in the sense of underestimating material aspects of economic life and in presenting an overly benign view which underestimates the instrumentality of most economic relations. It concludes with a reminder of the political significance of explanations of markets and competition.