By . In October 1993, in his first major speech as president of Yale University, Richard C. Levin talked about the importance of Yale’s becoming a “world university.” Great universities have a responsibility to drive global change, he said, and they achieve that primarily by nurturing future leaders and world-changing research inside their walled gardens. This spring, after two decades at the helm of Yale, Mr. Levin took a job as chief executive of Coursera, the online-education company. More...