 He did his postdoctoral work at the American School of Classical Studies in Athens, and became Evan Pugh Professor of philosophy at Penn State University and then Borden Parker Bowne Professor of Philosophy at Boston University.He has held the Companys Lectureship at the University of Barcelona, the Cardinal Mercier Lectureship at University of Leuven, the Priestley Lectureship at the University of Toronto, and the Gilson Lectureship at the Institut Catholique in Paris.He served as President of the Metaphysical Society of America in 1991.