Economists almost always assume that firms maximize profit. This idea has roots in Walrasian general equilibrium theory. The hypothesis of profit maximization is based on the notion that owners of firms are also consumers, and want the largest possible income to spend on consumption goods. The chapter highlights the importance of the assumption that markets are complete and competitive, and reviews some challenges to the assumption of profit maximization based on theories about firm organization. The Walrasian framework is inadequate for the study of labor-managed firms because it provides no linkage between the supply of inputs and control rights over firms. The rest of the chapter begins to construct these linkages. Control groups are defined to be sets of agents who both supply a particular input and also have a role in determining the firm's production plan. It is shown that under certain conditions, control groups will agree on profit maximizing production plans. In particular, this occurs when insiders can sell their share positions to outsiders, as long as the outsiders derive no net benefit from these transactions.