Technology is championed as the solution to modern security problems, but also blamed as their cause. This book assesses the way in which these two views collide in the debate over ballistic missile defense: a complex, costly and controversial system intended to defend the United States from nuclear missile attacks. Columba Peoples shows how, in the face of strong scientific and strategic critique, advocates of missile defense seek to justify its development by reference to broader culturally embedded perceptions of the promises and perils of technological development. Unpacking the assumptions behind the justification of missile defense initiatives, both past and present, this book illustrates how common-sense understandings of technology are combined and used to legitimate this controversial and costly defense program. In doing so it engages fundamental debates over understandings of technological development, human agency and the relationship between technology and security.