This book is an attempt to understand the nature of the European Union and of its claims as an autonomous polity. Although several similar attempts have been made in the past, the need to undertake such a task anew is particularly compelling in times of crisis. The reason is that one should not deny that the very idea of constitutionalism is at stake. Therefore, the book does not refrain from employing the language of crisis, although at the same time it purports to do so from a critical angle, in connection with the notion of security. In fact, some of the efforts made in the past have been incomplete, misguided, premature, or have themselves contributed to the failures of the EU. Far from providing an exhaustive picture of EU integration, this book nevertheless claims that security is a fundamental meta-constitutional rationale, which allows interpretation of both developments and challenges of the EU. Central for this analysis is the idea of discourses—in particular, the discourses of security and fundamental rights as discourses of power. Of course, law cannot be reduced to power. Of course, law cannot be reduced to discourse either. And yet, it is argued here, we should not rely too much on static models of integration through law. A change of perspective is advocated, which does not relinquish the EU constitutionalist mind-set.