Universities historically have supported the free and open exchange of ideas. Academic campuses, above all, are where free speech finds a home, where civil arguments are encouraged, places where a society shapes its values and principles. This enduring tradition inevitably ruffles the feathers of some, who fear the expression of beliefs contrary to their own.

The University of North Carolina, where I was privileged to teach for 22 years, struggled with this in the 1960s. The trouble started when state legislators, particularly from eastern and rural areas of the state, confronted students and others who challenged the state’s racist culture and the hierarchy of power. In 1963, legislators enacted a law that banned speakers on campus who were known to be members of the Communist Party or had invoked the Fifth Amendment in connection with congressional investigations of Communist activities. The ban was amended two years later to preserve the university’s accreditation, but students and others complained that the change simply passed responsibility for enforcing the ban from the legislature to university administrators.

At its northern end, this university’s property terminates at a brick sidewalk and a low stone wall that separates the campus from Franklin Street, Chapel Hill’s busy main stem. In the 60s, the students’ chapter of Students for a Democratic Society invited Frank Wilkinson and Herbert Aptheker to speak. Wilkinson had invoked the Fifth Amendment before the House Unamerican Activities Committee ( HUAC), and Aptheker, a widely published historian, was an avowed Communist. Wilkinson stood on the Franklin Street side of the stone wall and spoke to about 1,200 students crowding the edge of the campus. A week later, UNC Police Chief Arthur Beaumont stopped Aptheker as he began to speak on campus not far from Franklin Street and forbade him to speak on campus. So Aptheker, too, crossed to the other side of the low stone wall to give his talk.

Two years later a federal court in Greensboro declared the speaker ban unconstitutional, but the court offered some comfort to conservatives by pointing out that “extremist” speakers did not further the educational experience.

So here we are, 50 or so years later, still wrestling with the question of how free free speech should be, in society at large and in particular, on our universities’ campuses. Last week, New York Times columnist Bret Stephens wrote that if free speech is not vigorously defended, it quickly will erode, and he pointed to Robert Zimmer, president of his alma mater, the University of Chicago, who sees a depressing trend among many American universities, which are moving away from argumentation and challenge on campus. The University of Chicago, however, tilts in the opposite direction. In a 2015 report, a faculty committee on free speech issues, convened by Zimmer, found that the aim of education is to make people think, not to spare them from discomfort.

But today we find American universities fearful of offending, resorting to one state’s governor declaring a state of emergency in order to block a white supremacist from speaking. Other universities have put in place rules aimed at protecting the delicate sensibilities of students in their care from the voices of speakers who make them uncomfortable.

Universities, of all places, need to be the most vigilant of guardians of free speech because, as columnist Stephens correctly points out, “Free speech makes educational excellence possible.” If you can’t speak freely, you quickly will lose your ability to think clearly, Stephens wrote. “Your ideas will be built on a pile of assumptions you’ve never examined for yourself and thus may be unable to defend from radical challenges.” More importantly, he added, “You will be unable to test an original thought for fear that it might be labeled an offensive one.” I agree.

Bret Stephens earned his undergraduate degree in political philosophy at University of Chicago and a master’s in comparative politics at the London school of Economics. He is known as a conservative columnist and for being part of right-wing opposition to President Donald Trump.