The work of Thomas Kuhn (1962, 1970a) has attracted much interest from historians and philosophers of science because it offers a way to describe and evaluate scientific inquiry. For this reason it provides framework for determining whether the realist paradigm has adequately guided inquiry in international relations. Before the framework can be applied, a number of questions that have been raised critics of Kuhn must be addressed. The three most important how to define paradigm; whether Kuhn's description of scientific change is correct; and how paradigms can be evaluated. Each of these will be examined in this chapter.

Defining the concept of paradigm

Despite its wide use, the paradigm concept remains very difficult to define. The reason for this stems from its original usage by Thomas Kuhn in The Structure of Scientific Revolutions (1962). A textual analysis of that work by Margaret Masterman (1970) has shown that concept of paradigm was used by Kuhn in at least twenty-one different ways. In the postscript to the second edition of the book, Kuhn (1970a: 174–191) recognized this criticism and attempted to clarify the definition. He maintains that most of the varying usage is due to stylistic inconsistencies but concedes that even after these inconsistencies removed, the concept is used in two distinct ways: