In the period since the end of the Second World War, thinking about the ways in which development takes place and can be fostered has gone through a series of fundamental shifts, and in each of the paradigms that have been dominant at particular times the role of aid has been given a quite different emphasis. In this chapter the nature of each of these major periods in development thinking is outlined, along with an exploration of changing priorities for aid policy, and hence of the criteria that might be used to evaluate aid effectiveness. The aim, then, is to develop an understanding of the political economy of aid policy, moving well beyond restricted economic criteria to encompass political considerations as well as insights from a rang...