1972-1976 — Tutor, St. John’s College, Annapolis, Maryland

1973-1974 — Independent research on “Concepts of Organism, Species, and Health – Ancient and Modern,” supported by grant from National Endowment for the Humanities

1974-1976 — Joseph P. Kennedy, Sr., Research Professor in Bioethics, The Kennedy Institute of Ethics, Georgetown University

1976-1984 — Henry R. Luce Professor of the Liberal Arts of Human Biology, The College and the Committee on Social Thought, The University of Chicago

1984-1990 — Professor in The College and the Committee on Social Thought, The University of Chicago

1990-2010 — Addie Clark Harding Professor in The College and the Committee on Social Thought, The University of Chicago

(Also at The University of Chicago: Co-founder and Faculty Chairman [1983-2001], “Fundamentals: Issues and Texts” [undergraduate degree program]; Senior Fellow and Assistant Director, John M. Olin Center for Inquiry into the Theory and Practice of Democracy [1985-2005]; Senior Fellow, MacLean Center for Clinical Medical Ethics)