One southern winter evening in Buenos Aires, I met Dr. Conrado Varotto, father of Argentina's once-secret uranium enrichment program. “The bomb is in the human heart or it isn't,” he told me. “We could have done it, but we didn't, because the bomb was not in our hearts.” I was skeptical of Varotto's claim, but in the end, after a great deal of research and thought, I decided he was right. Indeed, in a sense this book is an extended elaboration on Dr. Varotto's basic point. It argues that decisions to go or not to go nuclear reflect the psychology of the leaders who make them. In particular, there are discrete decisionmaking pathways leading from different national identity conceptions, through emotions, to ultimate nuclear choices. This argument not only provides what I think is a powerful answer to the nuclear proliferation puzzle; it also provides a potentially fruitful basis for thinking about foreign policy decisionmaking more generally.

The project is nothing if not ambitious, and I am deeply grateful to the hundreds of people who have assisted and encouraged me to develop it. I owe a profound debt to the many politicians, scientists, civil servants, scholars, archivists, activists, and others who offered me their time and wisdom (and in some cases, their spare bedroom) as I struggled to discover the truth of their nations' nuclear histories. Some of these people are referenced directly in the text, but I am equally grateful to them all.