Pierre Hadot (1922-2010) was professor of the history of Hellenistic and Roman thought at the Collège de France. He was the author of many books, including Plotinus, or The Simplicity of Vision. Michael Chase is a senior researcher at the Centre National de la Recherche Scientifique-Centre Jean Pépin and adjunct professor of Greek and Roman studies at the University of Victoria. Arnold I. Davidson is Distinguished Professor of Humanities at the Hebrew University of Jerusalem as well as the Robert O. Anderson Distinguished Service Professor Emeritus at the University of Chicago. Daniele Lorenzini is associate professor of philosophy at the University of Pennsylvania.