Research and teaching interests include metaphysics, especially that of Aquinas and of Whitehead, as well as epistemology and philosophy of science. He has been the President of the Metaphysical Society of America, has published numerous articles and the following books:Making Sense of Your Freedom (Cornell U. Press, 1994, and Notre Dame U. Press, 2005) Coming To Be: Toward a Thomistic-Whiteheadian Metaphysics of Becoming (State University of New York Press, 2001); Human Knowing: A Prelude to Metaphysics (Notre Dame U. Press, 2005), Aims: A Brief Metaphysics for Today (Notre Dame U. Press, 2007)  and Adventures in Unfashionable Philosophy(Notre Dame U. Press, 2010)