Aldo Brancacci is Professor of Ancient Philosophy at the University of Rome Tor Vergata. He has published extensively on ancient Greek philosophy, including two books on Dio Crysostom (1986) and Antisthenes (1990, French rev. transl. Paris 2005). He edited a series of books on the philosophy of the Imperial Age, most recently Philosophy and Doxography in the Imperial Age (2005).Pierre-Marie Morel teaches History of Ancient Philosophy at University Paris I - Panthéon-Sorbonne. He has already published, among others, Démocrite et la recherche des causes (1996); Atome et nécessité. Démocrite, Epicure, Lucrèce (2000); Aristote, Parva naturalia, Introduction, French translation and commentary (2000), and several papers on ancient Atomism and Aristotle's psychology.