David T. Runia, D.Litt, Free University Amsterdam, is Professor of Ancient Philosophy at the University of Leiden and C.J. de Vogel Extraordinary Professor of Ancient Philosophy at the University of Utrecht. He has published extensively in the area of ancient philosophy, including Philo of Alexandria and the Timaeus of Plato (Brill, 1986) and Philo and the Church Fathers (Brill, 1995). Jaap Mansfeld, Ph.D. (1964) is Professor of Ancient and Medieval Philosophy at the University of Utrecht. He has published widely on ancient philosophy, its historiography and its reception, including Prolegomena (Brill, 1994).