Peter van Inwagen is the John Cardinal O'Hara Professor of Philosophy Emeritus at the University of Notre Dame. He is the author of two seminal works, An Essay on Free Will (1983), and Material Beings (1990), both of which are still in print.

William Lane Craig is Professor of Philosophy at Talbot School of Theology and at Houston Christian University. He has authored or edited over 40 books, including The Kal¿m Cosmological Argument; God, Time, and Eternity; and God and Abstract Objects, as well as over 200 articles in professional publications of philosophy and theology.