In the decade and a half since its initial formulation and development, securitization theory has evolved into a remarkably broad and vibrant area of research. Indeed, it is difficult to think of another perspective in security studies that could embrace (and virtually none that has embraced) the analysis of military affairs, the environment, gender, migration, and communications theory, to mention but a few, under a single theoretical orientation. Nor is it easy to think of another perspective in security studies that has generated such diverse and yet focused debates over its theoretical structure and empirical application.1 This book demonstrates that unity and diversity. Its contributors are united by need for a more sociological or pragmatic view of securitization. They share the view that if securitization theory is to reach its full potential, the formulations of the Copenhagen School are in need of further development and – in some cases – substantial redirection. Broadly speaking, it seems to me that these arguments run along two related lines. The first is that in its original form the idea of security as a speech act is constrained by a version of social theory that is too thin and too formal to capture the concrete dynamics, strategies, and forms that securitizing acts can take. The second, is that while the Copenhagen School stresses that securitization is an interactive process, where the relationship between securitizing actors and audiences is crucial, the theory leaves this dimension radically underdeveloped, with a resulting inability to see the different forms the securitizing acts take depending on the context and audience.