This chapter considers the possibility of analysing morality as a solution to the problem of market failure. Here, morality is viewed as the outcome of a rational bargain nested in a prisoners' dilemma. In his book Morals by Agreement, David Gauthier argues that morality can be the outcome of a rational bargain. The chapter takes up the possibility of deriving morality from rationality. Whatever the specific shortcomings of Gauthier's argument, its great power is in seeing the deeply instrumental nature of morality. Morality is a social construct devised to solve problems that arise from the logical structure of human interaction. Like much of our normative life, a defensible morality is tied up with mutual advantage in ways the market failure-prisoners' dilemma paradigm enables us to see — to which other ways of modelling the problem blind us.