Geoffrey Hellman is Professor of Philosophy at the University of Minnesota, having held appointments and visitorships at Indiana University, the University of Washington, the University of California, Irvine, and the University of Otago (NZ). In 1983 and ’85, he was Visiting Fellow at Wolfson College, Oxford, and in fall of 1987 he was Visiting Scholar in Beijing, China, lecturing on philosophy of science at universities and institutes in five cities around the country. After obtaining his A.B and Ph. D. in Philosophy from Harvard (Ph. D. 1972, dissertation prize), he collaborated with Frank W. Thompson on early papers (1975, ’77) explicating model-theoretically “supervenience” concepts (going by their label, “determination principles”) as yielding a more realistic idealization than Nagelian theory-reduction of the dependence of higher-level sciences on the basic physical sciences. This was followed by a series of papers in philosophy of physics, especially quantum mechanics, exploring concepts of randomness, the quantum logical program, and especially the implications and stochastic generalization of Bell’s theorem and experimental tests confirming quantum predictions. (The implications concern determinism, locality, and realism; a kind of "experimental metaphysics" as Shimony has put it). With Richard Healey, he edited Quantum Measurement: Beyond Paradox (vol. 17 of Minnesota Studies in Philosophy of Science, 1998). Simultaneously he developed a modal-structural approach in philosophy of mathematics, publishing Mathematics without Numbers in 1989 (Oxford), then further improving and advancing the approach in a series of papers spanning the next two decades. (The academy report of his election in 2007 to the American Academy of Arts and Sciences cited these latter two bodies of work.) He has also worked on assessing the adequacy of constructive mathematics vis-à-vis scientific applications, on predicative foundations of arithmetic (with Solomon Feferman), and, more recently, on the topic of pluralism in mathematics and implications for foundations. He continues to think about general topics in philosophy of science such as Bayesian confirmation, reasonable realism, physicalism, and unity of science.