Freedom of speech. The ability to express yourself. It's a cherished idea -- as well it should be. Most of us who live in liberal Western democracies think of it as a basic human right. People have fought and died for it. But now we may be in danger of losing it.

The threat is not coming from without -- from external enemies -- but from within. A generation is being raised not to believe in freedom OF speech, but rather that they should have freedom FROM speech -- from speech they dislike. This is a threat to both pluralism and democracy itself.

We see this in Europe where "sensitivity-based" censorship attempts to ban anything deemed hateful or even just hurtful, and to ban criticism of religion, especially Islam.But the United States, despite its strong Constitutional protections in the Bill of Rights is far from immune from the rising trend of suppression of speech, or what is sometimes called political correctness. This is especially true at America's colleges and universities, the place where our future leaders are educated and where you'd expect speech to be the most free.

Highly restrictive speech codes are now the norm on campuses, not the exception. According to a study by my organization, the Foundation for Individual Rights in Education -- FIRE -- 54% of public universities and 59% of private universities impose politically correct speech codes on their students. And thanks to recent Department of Education guidelines 100% of colleges may adopt speech codes in the coming years.

How bad is it?

At a public campus in California on Constitution Day in 2013, a student who also happens to be a decorated military veteran was told he could not hand out copies of the Constitution to his fellow students. The objection from the university was not ideological; it was out of control bureaucracy imposing limits on speech.

That same day another college student in that same state was told he could not protest NSA surveillance outside of a tiny "free speech zone," an area that comprised only 1.37% of the campus.

Months later, college students in Hawaii were told both they could not hand out the constitution to their fellow students and that they could not protest NSA policies outside the school's free speech zone! FIRE took these colleges to court, but the that fact we had to shows you how bad it has become.

Recently, students and sympathetic faculty have joined forces to exclude campus speakers whose opinions they dislike. At FIRE we call this "disinvitation season" although the season lasts all year round.

Since 2009 there has been a major uptick in the push by students and faculty to get speakers they dislike disinvited. These speakers have included former Secretary of State Condoleezza Rice; the Somali-born feminist and critic of Islam, Ayaan Hirsi Ali; and the director of the International Monetary Fund, Christine Lagarde. And that's only the obvious part of the disinvitation problem. Few conservative speakers are invited to speak at colleges lest they have to be "disinivited" later.

The newest threat to speech comes from so-called "trigger warnings" -- alerts that warn students that they are about to read or hear something that "triggers" a negative emotional response.

A 2014 NY Times article cited the example of a Rutgers student requesting "trigger warnings" for the classic American novel The Great Gatsby because it "possesses a variety of scenes that reference... abusive, misogynistic violence."

Recently, Oberlin College attempted to institute a policy that heavily encouraged the faculty to avoid difficult topics and to employ trigger warnings as a means of "making classrooms safer."

"Safety" has been watered down to essentially mean the "right to always feel comfortable." New demands for trigger warnings are popping up on campuses across the country.

Add in popular academic theories that encourage students to scrutinize speech for "micro aggressions -- any statement that might be construed as racially insensitive, classist, sexist, or otherwise un-PC -- and it's clear that campuses are teaching students to police what they say.

This is precisely the opposite of what is needed. Our society needs candor and it needs freedom of speech, not freedom from speech.

Intellectual comfort is not a right. Nor should it ever be. Not if we want freedom of speech -- let's just call it freedom -- to survive.

I'm Greg Lukianoff, President of the Foundation for Individual Rights in Education for Prager University.