‘The Diversity Principle’: Tracking the long history of a powerful idea

Through the early decades of the 21st century, the principle of diversity had broad influence, embraced in the United States by leaders at every level in politics, business, the military and education. But with a changing political climate, advocates have been muted and the idea has fallen into retreat.

In this challenging environment, a new book by Berkeley Law Professor David B. Oppenheimer is a compelling exploration of an idea that has galvanized some of the most grinding political and cultural conflicts of our time. The Diversity Principle: The Story of a Transformative Idea follows the history across a surprising 200-year span. Along the way, it profiles the famous scholars who gave birth to the idea and shaped its evolution, and details the essential role of universities and the law in its advance. 

At such a fraught time, the book could have been a partisan argument, but Oppenheimer’s approach is scholarly and accessible. The study is deeply documented, and the tone is measured. While he does not hide his embrace of diversity and his opposition to those who want to cancel it, his focus is on the philosophy and practical application of an idea that is too often oversimplified beyond recognition.

Oppenheimer describes diversity as the foundation for the “marketplace of ideas” — the clash of assumptions, hypotheses, values and knowledge that demands intellectual rigor and creates a real-life laboratory for understanding the world and solving its problems.

“The diversity principle holds that when you bring together people with different backgrounds and experiences, including people of different ages, of different religions, of different races and ethnicities and genders, when you include people with disabilities, when you include people who are perennially outsiders and make them all part of a group, they will be better problem-solvers,” he explained in an interview.

“In a classroom, they’ll generate more ideas. In a science lab, they will come up with more significant discoveries. In government, they will develop more original public policy initiatives. In a business, they’ll make more money.”

And, Oppenheimer says, there’s extensive scientific research to prove the point. What remains to be seen is how much evidence will be needed to persuade a powerful corps of diversity opponents.

Oppenheimer is a clinical professor of law and co-director of the Berkeley Center on Comparative Equality and Anti-Discrimination Law, and he has written extensively on issues of discrimination and how to address it through the law. His latest book was released on Feb. 24 by Yale University Press.

Legal issues of race and fairness have been a flashpoint throughout U.S. history, and certainly in the political and cultural wars since the zenith of the Civil Rights era more than 50 years ago. Despite steadily advancing support for the principles of diversity, the idea has faced a growing backlash from critics who suggest it’s a ruse for advancing people of color and women unfairly, at the expense of white people or men.

Initially, Oppenheimer was skeptical. If diversity was just a device for enrolling or hiring a few people from marginalized groups, he worried the approach would lead to tokenism. But some years ago, a colleague urged him to look more deeply. That challenge led to a sustained, deep dive — and to the discovery of a remarkable history that has propelled the idea through two centuries.

Tracing the history: Prussia, Washington, Berkeley

In Oppenheimer’s telling, the story begins with Wilhelm von Humboldt, the Prussian polymath, diplomat and educator. He founded the University of Berlin in 1810 with a revolutionary plan: Fewer lectures, less memorization. More debate, more experimentation. Such a culture required more diverse voices, so enrollment was opened to Jewish and Catholic students and faculty.

John Stuart Mill and his wife, fellow philosopher Harriet Taylor Mill, embraced those ideas. Nearly 50 years later, in their seminal work, “On Liberty,” Humboldt’s words are featured in the epigraph:

“The grand, leading principle, towards which every argument unfolded in these pages directly converges, is the absolute and essential importance of human development in its richest diversity.”

The Mills were enormously influential in American life in the mid-1800s, and especially in the anti-slavery movement. A central conclusion of their work, Oppenheimer said, is that the quest for truth requires people to test their own ideas and beliefs with people who have  different ideas and beliefs.

“The only way to see the world through the eyes of others,” he explained, “was to create what we now call a ‘marketplace of ideas’ by including a diverse group of people — not just Anglicans, but Unitarians and Catholics and Jews, and people from other countries.”

The Mills’ idea had revolutionary implications: Creating a free marketplace of ideas meant giving women the right to vote and allowing Jews to run for Parliament. It required freedom for Black people in the Caribbean and freeing Ireland from strict British rule.

In subsequent decades, the idea continued to unfurl. Charles Eliot was named president of Harvard in 1869 and is credited with transforming it from a sleepy college to a great center of learning. He opened Harvard to Catholics and Jews, Black people, immigrants and low-income students.

The famed jurist Oliver Wendell Holmes was educated at Harvard. He mentored two young attorneys, Felix Frankfurter and Harold Lasky, and together they read “On Liberty.” The book shaped Holmes’ landmark Supreme Court rulings on freedom of speech, and later, when Frankfurter was a Supreme Court justice, it shaped his writing on academic freedom.

Oppenheimer credits Berkeley-educated attorney Pauli Murray with a profound impact as a scholar and activist focused on racial and gender diversity. She was Black and queer, and today, many scholars believe, she may have identified as a transgender man. She faced a gauntlet of discrimination as she made her way through university and law school, but the experience forged a committed legal scholar. While earning a master of law degree at Berkeley in 1944 and ’45, she wrote the first law review article on sex discrimination in employment.

Through that paper and others, Oppenheimer writes, Murray’s work had an influence on legal titans such as Thurgood Marshall and Ruth Bader Ginsburg. Murray’s “hard-earned insights,” he writes, “made their way into some of the most important Supreme Court cases of the 20th century.”

Archibald Cox, famed for his role in holding President Richard Nixon accountable for the crimes of the Watergate scandal, was a student of Frankfurter’s. Returning to Harvard after Watergate, he wrote a legal rationale for affirmative action that was influential in the 1978 landmark case of Regents of the University of California v. Bakke, which upheld the constitutionality of affirmative action in college admissions.

That precedent held for 45 years, until 2023, when today’s conservative Supreme Court majority reversed it in two cases that effectively barred colleges from using racial considerations in student admissions.

A fundamental confusion

The core of the diversity principle is that diverse minds and diverse experiences, when applied to a problem, will lead to better understanding and better solutions for challenges across day-to-day life.

In the marketplace of ideas, competition sharpens insight and drives success. It’s an essential benefit, Oppenheimer says, that this opens the door for marginalized groups to have a stronger voice in the affairs of the nation.

Not so long ago, influential conservatives and Republicans embraced the idea. Supreme Court justices Lewis Powell, Sandra Day O’Connor and Anthony Kennedy each were appointed by Republican presidents, he writes, and each had written opinions upholding the right of colleges and universities to consider race and ethnicity in assembling a diverse student body.

Today, however, the terms of our debate — literally, the words we use — can reflect a fundamental confusion. Many contemporary critics of diversity use the word interchangeably with “affirmative action” or “quota,” though there are significant differences between them. In the Supreme Court’s 2023 case prohibiting affirmative action, the conservative majority, led by Chief Justice John Roberts, insisted that the law must be “colorblind.”

“But ‘color-blindness’ in a society with pervasive systematic racism is not a form of opposition to racism,” Oppenheimer writes. “It is simply racism-blindness.”

Oppenheimer drives home the point: In law and politics, diversity opponents are advancing the view that acknowledging race as a critical issue is itself racist, and that idea now inflames our politics. What does he see as the core of that paradox?

For some opponents of diversity in higher education, he writes, “it appears that the ultimate goal is to enroll fewer minority and more white students.”

The value of diversity, proven by research

While opponents often believe that diversity values unfairly put white people or men at a disadvantage, Oppenheimer argues that everyone stands to lose if the principle is undermined.

A significant section of his new book explores the growing body of research that shows how diversity creates advantages across a range of sectors: business, the military, health care, education, civic engagement and others. He details how leaders in those fields have embraced the principle in their own operations.

He identifies another UC Berkeley connection to the evolution of diversity values: Victoria Plaut, a social and cultural psychologist at the law school and vice provost for the faculty, has pioneered the field “diversity science.” Her work has explored the idea that for diversity to produce its best results, marginalized groups must have equity and inclusion.

“For the first 180 or 190 years, diversity was a philosophical theory,” Oppenheimer said. “It had not been empirically tested. But then starting about 30 to 40 years ago, people started testing the idea. We found that it really does work.”

His book details research that shows the diversity principle in action. For example, diverse groups do better in creative tasks than homogenous groups. The most successful scientific research labs are more likely to be diverse. Students in a diverse environment come up with more ideas — and they’re more comfortable in diverse environments.

“The science,” he concludes, “just gets stronger every year.”

Can our diversity inspire us to listen?

After his work on The Diversity Principle, and after years of research into discrimination law and policy, Oppenheimer knows that progress toward racial equality in the United States moves predictably from advance to backlash, in recurring cycles. Slavery, then an anti-slavery movement. Freedom for people who’d been enslaved, then the rise of Jim Crow. The passage of historic civil rights laws in the 1950s and 1960s, then campaigns to tap racial resentment among white voters. Barack Obama, then Donald Trump.

And so, while the landscape is challenging today, he is optimistic that, in time, diversity will return to favor.

“Unless we’re re-experiencing the fall of the Roman Empire and the beginning of the Dark Ages,” he said, “I have to think that we’ll come to our senses as a society and recognize the importance of this powerful idea.

“Does a country that has become the richest country in the history of the world — in significant part because of the strength of our diversity — decide to give that up and become a poor country? Does the country with the greatest universities in the world decide to disassemble those universities so that other parts of the world can be the home of the greatest universities?

“Diversity contributes so much to our success,” he said. “I hope it will help to put us on a path in which we do a better job of listening to each other.”