Alexander Heffner and his grandmother, Elaine Heffner, host and produce the long-running PBS show “The Open Mind.” Alexander's grandfather was the original host. (Andre Chung/for The Washington Post)

The dinner table, an Amtrak train, a television studio, a hotel lobby — Alexander and Elaine Heffner will have an intellectual discussion wherever you’d like.

On a Tuesday afternoon in Washington, a thunderstorm crashes outdoors. But it can’t drown out the lively conversation in the lobby of the Loews Madison Hotel between Alexander Heffner, the 26-year-old host of the 60-year-old PBS interview show “The Open Mind,” and Elaine Heffner, his 89-year-old grandmother and the show’s executive producer. Listening to their discussion is like showing up at a college seminar that you’ve skipped for half a semester: It feels familiar, but a lot of what’s being said goes over your head.

Harvard-educated Alexander, a journalist who previously interned for The Washington Post, and his psychotherapist grandmother converse in the realm of ideas and speak in the language of -isms; at one point, Alexander describes a childhood anecdote as exemplifying the “textualism versus living constitutionalism” debate. (To be fair, the story is about Alexander meeting Supreme Court Justice Stephen G. Breyer.)

What’s evident, however, is the family passion for civil discourse and a robust exchange of ideas — which they channel on “The Open Mind.” This year, somewhat serendipitously, the show’s 60th anniversary season coincides with the receipt of a $100,000 grant from the John S. and James L. Knight Foundation, which supports and funds journalism and media organizations. The show will use the money for a series of programs on freedom of speech and expression, which the Heffners believe is fundamental to a democratic society. It’s what makes a show like “The Open Mind,” which Richard Heffner founded in 1956 to promote open, free-ranging discourse, possible.

“I think we’re doing justice to his legacy,” Alexander says of his late grandfather, who died in 2013. “Dick is smiling at us,” agrees Elaine.

In the 1950s, Richard Heffner was a professor of history at the University of California at Berkeley and the host of a radio news program called “History in the News.” Television was then in its infancy, but seeing the medium as a potential virtual classroom, helping to disseminate ideas to people all across the country, he hit on the idea for a public-affairs TV show consisting entirely of interviews. “I think I’m going to call it ‘The Open Mind,’ ” he told his wife of six years.

“Even then, he was trying to follow in that track of an intellectually based, content-based, non-adversarial-based kind of interview,” remembers Elaine.

And so “The Open Mind” was born. Originally airing on an NBC affiliate in New York, it was one of the first interview-based television programs in the nation. It later moved to public television and found its current time slot in 1980: Sundays at noon on PBS, just after shows like “Meet the Press” and “Face the Nation,” which some might see as rather antithetical to the mission of “The Open Mind.” Through the years, guests have included prominent thinkers and innovators in every field and profession, although all are subjected to the same minimalist set — guest and host seated at a small table against a black backdrop — and maximalist attention to the conversation.

The most devoted pupil of the classroom that was Dick Heffner’s“The Open Mind” was his grandson, Alexander. When he was growing up, Alexander said, the show was a formative part of his education, providing an encyclopedia of sorts. Having a family connection to the uninhibited exploration of ideas made it “all the more intimate,” he says.

This intimacy became noteworthy during Dick’s final years as host. According to Elaine, Dick would often joke that he could call on his grandson to persuade reluctant guests to appear on the show. “He had a way of talking to people,” she says.

Since Alexander took over as host, the show, which now originates from CUNY TV studios in New York, has hosted such newsmakers as soul singer Aloe Blacc, TV writer/director Jill Soloway and Sen. Bernie Sanders.

That last guest caused some friction between Alexander and his grandmother. At the time of the March 2015 interview, Sanders hadn’t yet announced that he was running for president, but speculation that he might was rampant. After watching the episode, Elaine picked up the phone and called Alexander to remind him that the whole premise of the show was to engage with guests who had no ulterior motives for appearing.

Alexander is now committed to keeping the show free of political candidates, although current and former officeholders are fair game, he says. He imagines that campaigning politicians would be more likely to follow a teleprompter in their heads than to engage in free thought.

After working together for more than two years, grandmother and grandson now rarely disagree on production ideas and decisions, although they still frequently debate politics, philosophical ideas and personal beliefs. As evangelists for open discourse both on and off the screen, they’re concerned that the ability to respectfully disagree about ideas has been lost.

On the one hand, Alexander says, the wave of political correctness that has washed over college campuses and other areas of popular discourse makes disagreement taboo. “Political correctness is being equated with the Golden Rule,” he said.

On the other hand, Elaine believes that the anti-political­correctness camp has found an undesirable spokesman in Donald Trump. Instead of conveying his disagreement with respect, he chooses to make everything personal.

“Criticism has become equated with attacking and trashing the other person,” she said. “You have to establish the idea that you can disagree in a civil manner.”

This is the continuing stance of “The Open Mind,” even with a new host and 60 years under its belt. In an era that they fear will be dominated by hive-mindedness and clickbait and an unwillingness to listen, Alexander and Elaine Heffner fight to keep the search for new ideas alive and vibrant. They don’t always agree with their guests, they say, but they find it important and rewarding to engage with them anyway.

As Elaine says, “In order to teach, you have to be able to hear the other person.”