Previously an Associate Professor of History at the University of California, he completed his PhD in Medieval Studies at the University of Toronto in 2000, followed by three years of postdoctoral work at the Concejo de Investigaciones Superiores in Barcelona and the Institute for Medieval History at Boston University. He has served as President of the American Academy of Research Historians of Medieval Spain and is Book Review Editor (late medieval) for Speculum. His fields of research include medieval Spain and the Mediterranean, and ethno-religious identity and relations in the pre-modern Christian and Islamic worlds.