the views of Marx, Foucault, Wittgenstein and Nietzsche as well as sociologists of science such as Mannheim and Bloor. The author provides a wide interpretative framework which links the doctrines espoused by many of these authors; it is argued that they inherit many of the difficulties in the Strong Programme in the sociology of "knowledge", and that they fail to reconcile the normativity of knowledge with their naturalism. It is argued that neither relativists, sceptics, nihilists, sociologists of "knowledge" nor the postmodernists successfully debunk the claims of rational explanation, far from it: these theorists presuppose much of the theory of methodology they deny.