I am a historian of ancient philosophy, with a focus on the history of Platonism. I have also strong interests in Greek literature, especially tragedy, and Greek religion. I was educated at University of Marburg and at Cambridge University, where I received my Ph.D. in Classics in 1984. After a Junior Research Fellowship at Caius College, Cambridge, I taught briefly at UT Austin and for six years at the Freie Universit├Ąt Berlin. I joined the Princeton faculty in 1996. From 2006 to 2010 I served as Master of Forbes College.

My main publications are a reconstruction and interpretation of a sixth century anti-Aristotelian treatise, written by the Christian philosopher John Philoponus, and a study of the function of the gods in Euripidean tragedy. Most recently, I have edited volumes on such diverse topics as mysticism, Aristotle's cosmology, and the cult of Dionysus. My current researches focus on the history of Neoplatonism, on the development of the concept of evil in antiquity, and on pseud-epigraphical philosophical letters (Plato, Aristotle).

In addition to my research and teaching, I am serving as director of Princeton's Program in Hellenic Studies and as co-editor of two monograph series, Philosophia Antiqua (Brill) and Studien und Texte zu Antike und Christentum (STAC, Mohr-Siebeck). Together with Markus Asper, Berlin, I am also editing APEIRON, an international journal for the history of science and philosophy.