An earnest and daunting collection of essays, most of which attempt to bring contemporary social science to bear on weapons proliferation. Those not temperamentally inclined to explore the nuances of "structural realism" and competing doctrines may lose patience with some of the essays. Even readers who believe in the utility of theory in a world whose structure now seems quite uncertain may shake their heads at two essays that resort to formal modeling to explain nuclear proliferation. Still, some of the essays are useful. Richard K. Betts, for example, is a model of sobriety and insight in a revision of his well-known essay on "Paranoids, Pygmies, Pariahs and Nonproliferation." But by and large, one suspects that empirical research, which is represented but not dominant here, has more to offer students of proliferation.