Historians differ over the need to explore “counterfactuals”—the study of scenarios that never happened—and what they can tell us about historical causation. Stephen Kotkin, the Hoover Institution’s Kleinheinz Senior Fellow and noted historian of Russia, joins Hoover senior fellows Niall Ferguson and John Cochrane to discuss alternative historical outcomes: Stalin not surviving a two-front invasion in World War II and Churchill dying well beforehand; the American Revolution failing; the Beatles