José A. Cabranes, a judge on the U.S. Court of Appeals for the 2nd Circuit, was Yale University’s first general counsel and later served as a trustee of Colgate, Yale and Columbia universities.

Sixty years ago, Chief Justice Earl Warren warned our nation that we had a choice. Either “teachers and students must always remain free to inquire, to study and to evaluate,” or “our civilization will stagnate and die.” There was no third option.

Today, we face this choice again. Recent attempts to shame professors for unpopular views and to curtail the due process rights of those accused of misconduct are cause for alarm. Especially when academic freedom is endangered at places such as Yale — long celebrated as a leader on freedom of expression — we know that the erosion of academic freedom has become a national problem.

Academic freedom and the tenure system that protects it can seem unnecessary, even perverse, to the many Americans who lack job security. Why should professors be harder to fire than anyone else?

The short answer is that academic tenure is essential to democracy itself. A free society “depends upon the free search for truth and its free exposition,” as the American Association of University Professors noted in 1940. Tenure allows professors to pursue the truth and teach it without fear of retaliation.

Until recently, attacks on tenure came mostly from the political right. Cold War hard-liners pressured universities to crack down on “subversive activities” in the faculty lounge. Conservative intellectuals such as William F. Buckley Jr. derided “the superstitions of ‘academic freedom’ ” as protecting only anti-Christian and anti-capitalist lunatics.

The tables have turned. Academic freedom now attracts opposition largely from the left, while conservative organizations — including, ironically, the William F. Buckley Jr. Program at Yale — defend it most vigorously.

Certainly, today’s critics of academic freedom rarely deny that professors should be able to write and teach freely. But they nonetheless insist that professors should exercise such liberty in the shadow of other values, such as civility, sex equality and social justice. While these are worthy ideals, they can become tools for suppressing free expression — just as anti-communism once was.

No one can doubt that we should strive for civility. But problems arise when we are told that “uncivil” speech has made a campus “unsafe” — and that university officials should make a campus safe again by punishing uncivil speakers.

To combat these threats to “safety,” campus administrators have morphed into civility police. On some campuses, “bias response teams” investigate professors’ online comments. Several universities, including Yale, may soon introduce a smartphone app that lets users anonymously report offensive remarks. These anonymous reports will allow university bureaucrats — and perhaps even the public — to compile a directory of “subversive” professors in the spirit of dictatorial regimes. One can easily imagine dueling “watchlists” compiled by liberal and conservative activists with the shared aim of chilling unwanted speech.

At Yale and elsewhere, reports of sexual misconduct (and soon, perhaps, other offenses as well) end up in the hands of a centralized bureaucracy, which has the self-appointed obligation to retain them indefinitely — and to sift them for patterns of deviationism. The result is a university in which an unknown percentage of faculty members have been accused of something but don’t yet know it. It’s not hard to see how unscrupulous administrators might come to value the new “surveillance university” as a tool for policing the teaching and research of the professoriate.

I’m not naive. As Yale’s first general counsel, and later a trustee, I know that professors are no more virtuous than the rest of us, and that universities have a right, and often a duty, to detect and punish their offenses. The crucial question is not whether universities should discipline professors, but how.

Until recently, Yale insisted that accused professors enjoy basic due process, including the rights to a public, recorded hearing; to legal representation; to present evidence; to question opposing witnesses; and to a presumption of innocence unless convicted by “clear and convincing evidence.” Today, however, Yale and other universities routinely ignore or limit these rights, which the American Association of University Professors has described as essential in any fair proceeding. Yale now adjudicates sexual misconduct proceedings in secret. The standard of proof is reduced to “a preponderance of the evidence,” the lowest possible bar. And Yale made these changes without the formal consent or approval of its faculty.

Nobody can doubt that sexism, along with other forms of pernicious discrimination, can create problems on campuses. But universities can fight these evils without sacrificing the due process rights that have long guarded professors’ freedom to teach and write.

Yale knows this from experience. In the 1960s and 1970s, student activists demanded that Yale exclude noxious speakers from campus, including the segregationist governor George Wallace of Alabama. In response, Yale’s president appointed a committee chaired by the eminent historian C. Vann Woodward to examine freedom of expression at Yale.

The Woodward Committee issued a report that celebrated freedom of expression as a university’s primary obligation. Yale can and should create an inclusive campus, the report argued, but never at the cost of intellectual freedom.

Our universities today must pay more than lip service to free expression. They must develop and maintain procedures that protect professors’ ability to teach and learn without fear of retaliation. While political alignments may have flipped, the choice remains the same: academic freedom or civilizational decline.