structor in Humanities, Massachusetts Institute of Technology, 1957-60 Instructor in Philosophy, Princeton University, 1960-61, 1963 Assistant Professor of Philosophy, Rice University, Texas, 1965-66 Associate Professor and Director of Graduate Studies in Philosophy, Rice University, 1966-67 Associate Professor, University of California, Santa Barbara, 1967-68 Professor, University of California, Santa Barbara, 1968-present; Graduate Advisor 1968-70; Undergraduate Advisor 1976-80, 1988, 1990 to present.