Torstein Theodor Tollefsen is Professor of philosophy at the University of Oslo, Norway. His main interests are in ancient and late antique philosophy, Aristotle, Neoplatonism, and early Christian thought. He has published several articles on early Christian thought, especially on St Maximus the Confessor. He has published three books on Oxford University Press: The Christocentric Cosmology of St Maximus the Confessor (2008), Activity and Participation in Late Antique and Early Christian Thought (2012), and St Theodore the Studite’s Defence of the Icons: Theology and Philosophy in Ninth-Century Byzantium (2018).