He received a B.S in Physics from Massachusetts Institute of Technology and then went on to do graduate work in philosophy at Oxford and at the University of California (Berkeley), where he received a Ph.D. in Philosophy. He joined the Institute for Philosophy and Public Policy in the School of Public Policy at the University of Maryland in 1986 after teaching several years in the Philosophy Department at the University of Pennsylvania. From 1987 to 1991 he held a joint appointment with the Institute for Philosophy and Public Policy and the Maryland Biotechnology Institute's Center for Public Issues in Biotechnology. He joined the faculty of the School of Medicine in 2011.