Frederick Wiseman has been called America's greatest living filmmaker. It's a title that seems hard to argue.

Since 1967, Wiseman has directed 42 documentaries, most of them epic explorations of social life and institutions. These include "High School," "Hospital," "Basic Training," "Public Housing" and his latest, "National Gallery," which screens four times this weekend at Walker Art Center.

Despite their strict avoidance of voice-over narration and talking head interviews, Wiseman's films are extraordinarily articulate, as is the man himself. Indeed, to talk with him is to be in the company of the sort of teacher to whom one turns for advice on vitally important matters — not only about filmmaking, but nearly everything under the sun.

In conversation, Wiseman is full of stories, many of them funny — "Marry someone rich" is his advice to fledgling filmmakers — and all of them advancing his philosophy of life and art.

Speaking of "National Gallery" on a mid-September visit to Minneapolis, Wiseman began with a tale of fools, a warning to those of us who take art for granted.

"The Museum of Modern Art did a study a number of years ago and found that the average amount of time someone looks at a painting is two seconds," he said. "What can you possibly glean in two seconds? If you really want to figure out what the artist is trying to do, you have to stop and pay attention to every single aspect of the painting — the form, the color and the story, if there's a story."

Wiseman's own storytelling certainly rewards close inspection. "National Gallery," shot in and around London's centuries-old museum, might appear at first glance to be a minor work by the filmmaker, but it expands over the course of three hours into a complex and provocative rumination on what art means — or, more precisely, on how the meanings of art are made.

Wiseman said he has been thinking about the film for 25 years, ever since his plans to make a documentary about the Museum of Modern Art were derailed when the institution suddenly reversed its decision to grant him access.

It was only a couple of years ago when the 84-year-old Wiseman, while skiing in Switzerland, met a National Gallery curator who had seen his films and encouraged him to pursue making a movie there. For Wiseman, whose mastery of the film medium stems equally from careful calculation and an openness to spontaneity, this meeting signifies the significant role of chance in all of his work.

"The model is Las Vegas," he said. "Each film is a roll of the dice. If you're lucky enough, and persistent enough, you come across the most extraordinary sequences, with things you'd have to be a great writer to invent. Luck is what brings you there."

On the subject of luck, Wiseman said he felt fortunate to be in Minneapolis, realizing a dream. On the day of our interview, he was in town working with choreographer James Sewell on a ballet adaptation of his first film, "Titicut Follies," shot in an institution for the criminally insane.

On paper, the idea might sound, well, mad. But given the sizable role of offstage performance in so many of Wiseman's films, "Titicut Follies" not least, the project is brilliant.

"It's not weird to me at all," Wiseman said. "I think it's a natural extension of my interests. As a filmmaker, you can't help but be interested in movement. On this piece, I'm acting as a dramaturge, a consultant. Today was our first day of working with the dancers, and it's great. I'm enjoying it enormously."

Asked about recent advances in video technology and the so-called new age of documentary, Wiseman expressed his skepticism of both.

"The technology has allowed more people to make movies, but not necessarily better movies," he said. "In many ways, the documentaries that have quote-unquote made it commercially are the least interesting — because they're the documentary version of Hollywood movies. They're made for commercial purposes. I think people have every right to do that, and I have no objection to it being done. But because they're made for money, there's often an absence of complexity and ambiguity. And that is of no interest to me."

Wiseman acknowledged that, despite his decades of critical acclaim, his audience is much smaller than the one for, say, Michael Moore or Morgan Spurlock.

"I think if a couple of million people see my movie on public television, that's a big audience," he said. "But it's nothing compared to what comes from theatrical exhibition. If two million people paid to see my movie in the theater, I'd be delighted."

With that, Wiseman waits a moment, and then, with a sly smile, delivers the punch line. "I could have my own jet."