In 1999, a young PhD candidate in philosophy named Nick Bostrom published an article in Mind entitled “The Doomsday Argument is Alive and Kicking.” The article asked whether probabilistic attempts to predict when the last human being would be born were reasonable. (They were, it argued.) The title, however, signaled something far more significant: the end of post–Cold War optimism. Human extinction was back on the menu.
In the years following the Mind article, Bostrom’s star would rise. He was instrumental in founding at Oxford the academic think tank Future of Humanity Institute, devoted to preventing human extinction. Seven years later, his work would help inspire the founding at Cambridge of a second such institute, the Centre for the Study of Existential Risk. By 2015, Bostrom had made Foreign Policy’s “Top 100 Global Thinkers” list for the second time.
Largely thanks to Bostrom and a battery of his associates, the study of “existential risks” — threats that could bring...