The debasement of liberal education is a little-discussed but long-standing cause of the much-discussed polarization of our politics.

The historically high unfavorable ratings of the 2016 presumptive Republican and Democratic presidential nominees underscore this polarization. Staggering numbers of voters (approximately 65 percent) disapprove of GOP front-runner Donald Trump. The unfavorable ratings of the Democratic Party’s presumptive nominee, Hillary Clinton, lag not too far behind.

Several factors fuel voters’ dyspeptic mood. For decades our two-party system has been undergoing an ideological sorting whereby conservatives in the Democratic Party have migrated to the Republican Party and liberals in the GOP have found their way to the Democrats. As their direct experience with differing viewpoints declines, party members grow more intolerant of those who bring to politics competing perspectives.

Meanwhile, many working-class whites, who have been suffering from stagnant wages and high unemployment, have grown convinced that the Washington political establishment—Republican as well as Democratic—ignores their voices and disregards their interests. And a considerable percentage of the millennial generation believes that the Wall Street establishment deprives them of their fair share of American prosperity.

As traditionally conceived, liberal education would temper the all-too-common tendency to demonize those fellow citizens with whom we disagree. In no small measure, the value of a liberal education—to the individual and to the public—stems from the ability it cultivates to explore moral and political questions from a variety of viewpoints. This virtue entails putting oneself in another’s shoes. It promotes toleration, civility, and mutual respect. In “On Liberty,” John Stuart Mill called this the virtue of “many-sidedness.”

However, as currently practiced at our leading colleges and universities—through which a disproportionate percentage of our elites pass—liberal education cultivates single-sidedness and reinforces the polarization of our politics. The campus assault on free speech, the abandonment of the fundamental requirements of due process in university disciplinary procedures regarding accusations of sexual misconduct, and the hollowing and politicizing of the curriculum have become distressingly entrenched features of academic life. Their toxic effects are harming the country.

The assault on freedom of speech comes in many guises. To regulate expression and enforce orthodoxy, colleges and universities divide campuses—which ought to be havens for robust exchange of opinion—into expansive “safe spaces” and cramped “free speech zones.” They institute “trigger warnings” so students can avoid disturbing facts and ideas. They police “micro-aggressions”—that is, giving offense however unintentional, slight, and subjective. They exalt diversity of race, ethnicity, and gender as a supreme value, while invoking the gentle notion of “inclusion” to exclude ideas and individuals who dissent from progressive orthodoxy. They strong-arm students and faculty who fail to fall in line. This zealous administrative oversight of thought and discussion teaches students to be both hypersensitive and hypercritical.

In disciplinary proceedings, many universities—prodded by official directives from the Obama administration’s Department of Education that threaten federal investigation and the loss of federal funding for failure to comply—have abandoned due process protections in favor of a presumption of guilt. Government officials, like the university faculty and administrators who molded their minds, have internalized the doctrines of Catharine MacKinnon who, more than 25 years ago, argued in “Toward a Feminist Theory of the State” that all sex is presumptively sexual assault because in a “male supremacist” society it is doubtful that women are capable of giving meaningful consent.

The theory that women are pervasively subjugated justifies the abandonment of due process: emergency circumstances justify emergency measures. It impels universities to impose on men the responsibility to obtain affirmative consent—yes means yes—at every stage of sexual relations. And it explains why affirmative consent is never enough.

Affirmative consent as applied by our universities is a snare and a delusion, because a yes can always be reinterpreted as coerced, and the authorities at our universities are only too ready to reinterpret apparent affirmations of consent as expressions of women’s vulnerability and dependence.

By jettisoning the distilled traditional wisdom about the elements of fundamental fairness in a free society, higher education prepares students—female and male—to submit to authority rather than hold it accountable.

Meanwhile, the elimination of a mandatory core curriculum leaves students ignorant of their own civilization as well as of other civilizations and without a common fund of knowledge with which to articulate their agreements and disagreements. Take, for example, the Constitution—knowledge of which is essential to serious political debate. Many of our finest colleges and universities do not require study of the principles of American self-government and they offer few elective courses in which students can obtain such knowledge.

The hollowed curriculum is also politicized, as much by the conservatism it excludes as by the progressivism it promulgates. Rare is the course that features one of the figures that shaped modern American conservatism let alone explores the unfolding of the conservative tradition in the writings of, say, Friedrich Hayek, Russell Kirk, William F. Buckley, Frank Meyer, and Irving Kristol.

Worse still, colleges and universities devote little attention to teaching the truly liberal principles that explain why the study of conservative ideas is vital even, or especially, for non-conservatives. The classic of the genre, Mill’s “On Liberty,” has fallen into desuetude. So has respect for his key contention: “He who knows only his own side of the case knows little of that.”

The exclusion of conservative ideas from the college curriculum is illiberal in effect and often in intent. This carries dire political consequences. It teaches students who lean left to despise conservative voices as unworthy of serious discussion. It generates anger and bitterness among conservative students, who see their opinions scornfully dismissed. And all around it fosters intolerance, incivility, and mutual contempt.

Small wonder that our public discourse is corrupted and our politics are polarized.

To provide a properly liberal education, colleges and universities must reform the curriculum by introducing all students to the principles of moral, political, and economic freedom; the controversies and continuities that constitute American history and the history of Western civilization; and the diverse beliefs and practices of other civilizations. Colleges and universities must also govern campus life on the premise that students are free and equal individuals, not victims and oppressors; this means upholding fundamental fairness and due process in all campus disciplinary procedures. And our colleges and universities must institutionalize the unfettered exchange of ideas.

Truly liberal education serves students’ interests and advances the public interest. It would form a citizenry more likely to attract, and be attracted to, worthy candidates for elective office.

Peter Berkowitz is a senior fellow at the Hoover Institution, Stanford University. This op-ed adapts recent talks on related topics at a Stanford Law School conference on civil liberties and the university; at the University of Chicago Law School sponsored by The Federalist Society; and at Prospectus, a national conference on the future of conservatism organized by Harvard undergraduates.