Alvin Plantinga is John A. O'Brien Professor of Philosophy at the University of Notre Dame. He is widely known for his work in epistemology and philosophy of religion, and is the author of Warranted Christian Belief (2000). He is also editor (with Matthew Davidson) of Essays in the Metaphysics of Modality (2003).

Michael Tooley is Distinguished College Professor of Philosophy at the University of Colorado, Boulder. He is well known for his work in metaphysics and applied ethics, and is the author of Time, Tense, and Causation (1997) and editor of Metaphysics (5 volumes, 1999).