ON A WARM morning in early spring, June Huh walked across the campus of Princeton University. His destination was McDonnell Hall, where he was scheduled to teach, and he wasn’t quite sure how to get there. Huh is a member of the rarefied Institute for Advanced Study, which lies adjacent to Princeton’s campus. As a member of IAS, Huh has no obligation to teach, but he’d volunteered to give an advanced undergraduate math course on a topic called commutative algebra. When I asked him why, he replied, “When you teach, you do something useful. When you do research, most days you don’t.”