I would like to have witnessed the explosion at Alamogordo, on July 16, 1945, for at that moment the history of the past met the history of the future as the two had never met before. Science had then achieved its most visible and awful triumph. On that account, a knowledge of history became indispensable as the surest way in which men and women might learn to understand their limitations—though they have yet to do so—and might thereby prevent the extermination of life on this earth.