The threat to free speech in the United States is by no means restricted to colleges and universities, but they have become breeding grounds, training camps, and launching pads in the campaign to curtail liberty of thought and discussion. It is on our campuses where the battle for free speech will be won or lost.

In this year alone, protesters at Claremont McKenna College disrupted a talk by the Manhattan Institute’s Heather Mac Donald; protesters at Middlebury College intimidated American Enterprise Institute Scholar Charles Murray and assaulted his host, Professor Allison Stanger; and, in the successful effort to prevent journalist and right-wing provocateur Milo Yiannopoulos from speaking, protesters at the University of California, Berkeley set private property aflame in a rampage across campus.

These are the tip of the iceberg. For a 2017 report, The Foundation for Individual Rights in Education “surveyed publicly available policies at 345 four-year public institutions and 104 of the nation’s largest and/or most prestigious private institutions.” A disheartening 39.6 percent “maintain severely restrictive, ‘red light’ speech codes that clearly and substantially prohibit constitutionally protected speech.”

Administrators and faculty have conspired to produce an intellectual environment hostile to free speech. The educational authorities teach students to demand trigger warnings for potentially disturbing subject matter; to perceive opinions with which they disagree as forms of “violence” and to scrutinize everyday utterances for actionable microaggressions; to expect the establishment of public “safe spaces” that exclude disfavored opinions; and to disinvite speakers who depart from campus orthodoxies.

Some high-ranking university officials have gone so far as to tout the policing and curtailment of expression as victories for free speech. In April, in a lengthy New York Times op-ed, “What ‘Snowflakes’ Get Right About Free Speech,” Ulrich Baer -- vice provost for faculty, arts, humanities, and diversity, and professor of comparative literature at New York University --advanced a supposedly more “sophisticated understanding.”

If “views invalidate the humanity of some people,” he asserted, “they restrict speech as a public good” and so these humanity-invalidating views, he contended, should themselves be restricted to improve free speech. The traditional name for Baer’s policy is censorship.

Commentary magazine’s summer feature “Symposium: Is Free Speech Under Threat?” canvasses a diversity of opinion on the subject, including the academic establishment’s studied obliviousness to the danger. Despite the massive evidence, First Amendment scholar and Columbia University President Lee Bollinger assures in his contribution that the threat is the invention of demagogues. “I do not for a second support the view that this generation has an unhealthy aversion to engaging differences of opinion,” Bollinger writes. “That is a modern trope of polarization, as is the portrayal of universities as hypocritical about academic freedom and political correctness.”

Yet the bulk of the Commentary symposium—which includes 27 distinguished writers, scholars, broadcasters, and university presidents—reveals just the opposite. It illuminates a wide variety of threats to free speech while recognizing—especially in essays by New York University law professor Richard Epstein, Brooklyn College and CUNY Graduate Center history professor K.C. Johnson, and Mac Donald—that the struggle on campuses is pivotal.

“Our greatest current threat to free expression is the emergence of a national culture that accepts the legitimacy of suppression of speech deemed objectionable by a segment of the population,” writes symposium contributor Robert Zimmer, president of the University of Chicago. “University and college campuses present a particularly vivid instance of this cultural shift,” he affirms, while noting that his school has taken a leading role in preserving the culture of free speech through its 2015 publication of the Chicago Principles. These declare that “the University’s fundamental commitment is to the principle that debate or deliberation may not be suppressed because the ideas put forth are thought by some or even by most members of the University community to be offensive, unwise, immoral, or wrong-headed.”

Other symposium contributors warn of threats to freedom of speech from beyond the campus. First Amendment lawyer Floyd Abrams observes that when President Trump “engages in daily denigration of the press, when he characterizes it as the enemy of the people, when he repeatedly says that the libel laws should be ‘loosened’ so he can personally commence more litigation, when he says that journalists shouldn’t be allowed to use confidential sources, it is difficult even to suggest that he has not threatened free speech.” At the same time, Abrams advises that the example set by the Obama administration, which “prosecuted more Espionage Act cases against sources of information to journalists than all prior administrations combined,” may invite still more extensive abuse.

For Nicholas Lemann, a professor at Columbia Journalism School and a staff writer for the New Yorker, “the number-one threat to free speech” stems from the control that Facebook and Google increasingly exercise over Internet content. On balance, however, Lemann believes that social media platforms have done considerably more good than harm. “We are in the middle of a free-speech explosion, because of 20-plus years of the Internet and 10-plus years of social media,” he says. Echoing the views of Lee Bollinger, his school’s president, Lemann asserts that their university has been “blessedly free of successful attempts to repress free speech.” He boasts that “just in the last few weeks, Charles Murray and Dinesh D’Souza have spoken here without incident.”

This is surprisingly parochial. The suggestion that hosting brief one-time visits by two conservative thinkers without sparking student incivility or violence is a noteworthy achievement—rather than the bare minimum expected in a culture of free speech—is itself telling evidence of the campus crisis.

Longtime Commentary contributor Michael J. Lewis argues that free speech is “everywhere threatened by regulation, organized harassment, and even violence.” The reason, he contends, is that the habits of free speech on which the right of free speech depends have been shriveled by the courts, which have removed controversial questions of public policy—such as abortion, same-sex marriage, and countless administrative regulations—from the political realm and confined them to the judicial realm.

Northwestern University Professor of Communications Laura Kipnis issues a salutary warning to conservatives. In her own words “a left-wing feminist professor,” she found herself accused of creating a “hostile environment” in violation of federal law by publishing a critique of “sexual paranoia” on campus. A tad uneasy with her new allies on the right, she exhorts conservatives, who have been at the forefront of the struggle to save free speech on campus, to ensure that their dedication to the First Amendment and the vigorous exchange of ideas is principled and not the opportunistic pleadings of a beleaguered minority that, if given the chance, would crack down on the speech of others.

Brookings Institution Senior Fellow Jonathan Rauch makes the excellent point—affirmed also in contributions by FIRE co-founder Harvey Silverglate and National Review Senior Editor Jonah Goldberg—that even as new perils have arisen, free speech is under threat today because “it is always under threat.” As Rauch observes, it is counterintuitive to think “that speech that is offensive, untruthful, malicious, seditious, antisocial, blasphemous, heretical, misguided, or all of the above deserves government protection.” Nevertheless, “the marketplace of ideas turns out to be the most powerful engine of knowledge, prosperity, liberty, social peace, and moral advancement that our species has had the good fortune to discover.”

That’s empirically verifiable. But it is a truth rarely heard on campus, which is a major reason why freedom of speech is under threat in America.