Alexander R. Pruss is Professor of Philosophy at Baylor University. His books include The Principle of Sufficient Reason (Cambridge, 2006), Actuality, Possibility and Worlds (Continuum, 2011), One Body (Notre Dame, 2012), and Necessary Existence (with Joshua Rasmussen; Oxford, 2018). He has PhDs in mathematics (British Columbia) and philosophy (Pittsburgh), and his current research focuses on metaphysics, philosophy of religion, formal epistemology and philosophy of mathematics.