Both the interest and the complexity of the study of public policy lie in its propensity to disrupt disciplinary boundaries, and to call for examination of the social, economic and political environment in which the state operates. The search for a general explanatory theory of public policy necessarily implies a synthesis of social, political and economic theories, for ‘what governments do’ embraces the whole of economic, social and political life. Public policies do things to economies and societies, so that ultimately any satisfactory explanatory theory of public policy must also explain the inter-relations between the state, politics, economy and society. This is also why people from so many ‘disciplines’ - economics, politics, sociology, anthropology, geography, planning, management and even applied sciences - share an interest in and make contributions to the study of public policy. But synthesis here becomes a matter of considerable controversy: the scale of interest and intellectual development allows speculation, hypothesis, theorising, argument, much of it brilliant and suggestive; but our state of social knowledge is such that no one theory is capable of proof. Theories themselves may become both heuristic tools and practical ideologies: a good example is provided by Marxist and neo-Marxist political economy. This complexity breeds competition between theories, conflicts over methods, and disagreement over what constitutes the proper mode of analysis.1