He received a doctorate in modern European history from the University of California-Berkeley in 2000 and a law degree from Harvard University in 2001. He came to Yale from Harvard University, where he was Jeremiah Smith, Jr. Professor of Law and Professor of History. Before this, he spent thirteen years in the Columbia University history department, where he was most recently James Bryce Professor of European Legal History.

In intellectual history, he has worked on a diverse range of subjects, especially twentieth-century European moral and political theory. He has written several books in his fields of European intellectual history and human rights history, including The Last Utopia: Human Rights in History (2010), and edited or coedited a number of others.