A noxious and surprisingly commonplace myth has taken hold in recent years, alleging that elite universities have pursued diversity at the expense of scholarly excellence. Much the reverse is true: Efforts to grow and embrace diversity at America’s great research universities have made them better than ever. If you want excellence, you need to find, attract, and support talent from every sector of society, not just from privileged groups and social classes. As the president of Princeton University, I see the benefits of that strategy on a daily basis—and never more vividly than when Princeton recognizes its most accomplished alumni. Later this month, for example, the university will honor Fei-Fei Li, a Chinese American immigrant who spent college weekends helping with her family’s dry-cleaning business, and now co-directs Stanford’s Institute for Human-Centered Artificial Intelligence. Li exemplifies the connection between excellence and diversity, as do other recent Princeton-alumni award recipients, including American Civil Liberties Union Executive Director Anthony Romero, who grew up in a low-income housing project in the Bronx; Ariel Investments’ co–chief executive officer, Mellody …