Ann Whitney Olin Professor of History at Barnard College, Columbia University, and a Fellow of the Medieval Academy of America. His most recent book is A History of Balance, c. 1250–1375: The Emergence of a New Model of Equilibrium and Its Impact on Thought (Cambridge University Press, 2014). This book was awarded the 2015 Jacques Barzun Prize in Cultural History by the American Philosophical Society. In 2017, it was awarded the Charles Homer Haskins Medal, the annual book prize of the Medieval Academy of America.