Research into politics is the art of the possible, and of all the possible approaches open to the political scientist in pursuit of some of the timeless questions of the discipline, the study of the fiscal and budgetary policies of government is one of the most vital. This is because it reflects such fundamental aspects of government as the setting of priorities, the allocation of resources, and the scope of the public sector itself. In other words, the fiscal approach provides one way of answering the primordial question: Why do governments vary in the policies they pursue? Until a decade or so ago, it is fair to say that most political scientists assumed that the primary determinants of public policy were political, and they therefore confined their attention to political institutions and processes, especially to legislative and pre-legislative politics. But a change has now taken place and attention has shifted to post-legislative politics; to, as it were, the object of the whole political exercise, to services, to policy, and to outputs. And instead of assuming that all can be explained by political factors, the causal nexus has been opened up to see how far underlying, non-political characteristics bear upon policy.