The billion-dollar standoff between the Trump administration and Harvard features stark disagreements — and at least one two-word point of convergence: “viewpoint diversity.”

In its letter last month threatening to cut Harvard’s federal funding, the administration accused the university of lacking it, and demanded that Harvard submit to a thorough external audit of the problem.

“Each department, field or teaching unit must be individually viewpoint diverse,” the letter said. So too must be the student body, staff and leadership. A failing grade, the letter warned, would result in corrective measures, including the deliberate recruiting of “a critical mass” of new faculty and students to correct the imbalance.

Harvard has rejected the Trump administration’s demands, calling them a threat to academic freedom and the political independence of higher education. But in a letter to Harvard affiliates informing them that the university was suing the government, Harvard’s president, Alan Garber, echoed that vocabulary.

“We acknowledge that we have unfinished business,” Dr. Garber wrote. “We need to ensure that the university lives up to its steps to reaffirm a culture of free inquiry, viewpoint diversity and academic exploration.”

The term viewpoint diversity, which also appears multiple times in Harvard’s recent report on antisemitism, may be unfamiliar to many. But it has been circulating in higher education for the past decade, prompting debates of its own.

For some, greater viewpoint diversity is needed to counter what they see as a rising censoriousness on many campuses, where intolerant students and an increasingly left-leaning professoriate stifle open debate. But to others, it’s a vague, politically coded term that misstates the problem while helping to fuel conservative attacks on universities and on racial, ethnic and gender diversity efforts more broadly.

Harvard itself has been a hotbed of diverse views about the value of viewpoint diversity and its relationship to the bedrock value of academic freedom. But there’s broad agreement that the Trump administration is weaponizing the term — which its letter never defines — in a dangerous way.

“Viewpoint diversity is a crucial, but difficult and subtle, ideal in intellectual discourse,” said the Harvard psychologist Steven Pinker, a longtime critic of higher education’s liberal tilt. But imposing it by government fiat, he said, opens the door to outcomes that are Orwellian, ridiculous or both.

“There’s nothing to prevent the party in power from enforcing the teaching of ideas that are both flaky and congenial to the administration: vaccine denial in medicine, 2020 election conspiracies in history, creationism in biology, quack nutritional theories in public health, the benefit of tariffs in economics, and so on,” he said.

The term viewpoint diversity began gaining currency across academia largely through the efforts of Heterodox Academy, a nonpartisan national group founded in 2015 to combat what it describes as “the rise of closed-minded orthodoxies within scholarly communities.”

In recent years, it has been picked up by Republican politicians, as a new tool to support their longstanding argument that universities have been taken over by the left.

“Have institutions, including the university system, been so thoroughly captured by anti-American and illiberal ideology that the government must step in to restore viewpoint diversity, free thought, and free expression?” U.S. Representative Virginia Foxx, a North Carolina Republican and at the time chairwoman of the House Committee on Education and the Workforce, wrote in The Washington Examiner in September 2023.

Since then, at least eight states have proposed or passed legislation seeking to mandate viewpoint diversity (or “intellectual diversity,” as some laws put it) at public institutions. The requirement is usually paired with demands that colleges ban diversity, equity and inclusion programs and restrict teaching on race and gender.

A report last October by the free expression group PEN America said that viewpoint diversity, while a laudable goal, has too often served as “camouflage” for the real purpose: stifling faculty members’ speech.

PEN America and others have raised particular alarm at a 2024 Indiana law which says that professors at public universities, including those with tenure, could be disciplined or fired if they failed to “foster a culture of free inquiry, free expression and intellectual diversity.” Last month, the state began what appears to be one of the first investigations under the law, involving a pro-Palestinian professor at Indiana University who had been anonymously reported for criticizing both the university and Israel during class.

“What we’re seeing now is very dangerous,” said Jonathan Friedman, the managing director of U.S. free expression programs at PEN America. “When you attach these punitive potential actions to these concepts, you can comb through anything a university is doing and find fault.”

Since getting the Trump administration letter, Harvard has emphasized its own efforts to broaden discussion on campus. It has sponsored a welter of initiatives and committees relating to “civil discourse,” “intellectual vitality,” “dialogue across difference” and the like, including some that began before the campus tumult associated with the Israel-Hamas war.

Until recently, the term “viewpoint diversity” rarely occurred in formal statements by the Harvard administration. And even as Dr. Garber has embraced it, it inspires some skepticism on campus, where to some it carries right-wing connotations.

Ned Hall, a philosophy professor who is co-president of the Council on Academic Freedom, a faculty group, said that while it is valid to worry about the ideological composition of the faculty, he finds the term vague and not particularly helpful.

“If you just latch onto a term, whether it’s viewpoint diversity or inclusion, it’s a place-holder where you get to fill in the details as you wish,” he said. “And — surprise, surprise — it can be affected by a political agenda.”

Professor Hall said he prefers to emphasize what he calls “collaborative disagreement.”

“You could imagine a campus that’s really diverse, but nobody talks to each other,” he said. “What we really, really, really need is a campus intellectual culture that makes use of that diversity.”

Research cited in a recent report on Harvard’s classroom environment gives a mixed picture of how much of that actually happens at Harvard. In a 2024 survey of seniors, only a third said they felt comfortable “expressing opposing views about controversial topics” in class or in their residential communities. About half as many conservative students said they felt comfortable. (Though some seem to relish the challenge. “Being Republican at Harvard has never been better,” the president of the thriving campus Republican club wrote last year in the campus newspaper.)

But a separate survey asking all undergraduates to evaluate their courses was more sanguine. More than 90 percent of respondents said they felt free to express their opinions in class, and 80 percent agreed that most fellow students “listen attentively with an open mind.”

Ari Kohn, a junior majoring in philosophy and social studies, said it can actually be easier to speak freely in courses than in dorms and dining halls, given that classes, particularly more specialized ones, tend to attract people with similar interests and outlooks.

“I think I do stifle my opinions more when I’m not in class, or other places where I know other people have read the same things,” she said.

But Ms. Kohn, who helps lead a campus group dedicated to fostering respectful dialogue, said that news media accounts often exaggerate the rigidity of student views.

“There’s a lot of talk about Harvard as a liberal bastion, and it is,” she said. “But it’s just as true that many students become more conservative or moderate. Over four years, you start to see things with greater complexity, and question your assumptions. That happens way more than the dominant narrative has it.”

As the Harvard administration embraces the ideal of viewpoint diversity, it remains unclear what that means for the fraught topic of Israel and the Gaza war.

The phrase “viewpoint diversity” and close variants occur dozens of times in the university’s report on antisemitism, which describes a “disturbingly one-sided” view of Israel and the Palestinians in some academic programs. Many of the antisemitic events described in the report, it says, stem from “insufficient respect for viewpoint diversity.”

Such references occur less frequently, and more skeptically, in the university’s parallel report on Islamophobia released at the same time. Some community members, the report notes, said the university’s stated goal of balanced perspectives was being used “not to foster a wider range of viewpoints but rather to suppress specific views.”

For some on campus, recent moves by Harvard leadership have reinforced that impression. In late March, as pressure from the Trump administration was building, Hopi E. Hoekstra, the dean of the Faculty of Arts and Sciences, sent an email to leaders of nondepartmental centers and institutes saying they should be prepared to answer questions about how their programs exposed students to “diverse viewpoints.”

The next day, the faculty leaders of the Center for Middle Eastern Studies, whose programs had been accused by some prominent Harvard affiliates of promoting antisemitism, were dismissed. (Dr. Hoekstra, after an outcry from some faculty members, defended the removals as part of “addressing the needs of our academic units.”) The university also suspended a program at Harvard Divinity School that had drawn similar criticism.

The next move in the standoff between Harvard and the government is unclear. But in a letter last week introducing the antisemitism and Islamophobia reports, Dr. Garber returned to a now-familiar theme.

Among his pledges: to “speed the establishment of a university wide initiative to promote and support viewpoint diversity.”