While movie buffs know Paul Schrader as the guy who wrote Taxi Driver, more deep-dive film scholars know him as the onetime critic who wrote a defining book about what's called the transcendental style in film.

That's a little weird, because the two reside at different ends of the movie spectrum — Taxi Driver and other Schrader films, like Light Sleeper, are visceral, emotional, sexual, violent. His 1972 book Transcendental Style in Film, just reissued with a new forward, discussed movies by Bresson, Ozu, and Dreyer that advance a spiritual idea or induce a spiritual state by sometimes doing nothing at all — no music, no conventional action, and many scenes of extended concentration on a static image. They are meditative by design, so much so that they are  sometimes called slow cinema.

These movies were so against the grain of Schrader's natural instincts as a filmmaker that he swore he'd never make one.

Until he did — called First Reformed, opening here Friday, and widely hailed as one of Schrader's best.

"I'd written about those movies, I've loved those movies, but I said over and over again, with sincere conviction, that I'd never make that kind of movie. I don't connect that book to what I do," Schrader said. "But suddenly I began to think of it as more of a life decision. Three years ago, I was waking on the streets of New York and thinking, you're going to be 70 next year. It's time to make that movie you swore you would never make."

Certainly, he made the attempt in First Reformed, and it has the technical elements of transcendental work. There is no added music, there are lots of static shots and subdued performances — all in the service of an austere story about the Protestant pastor (Ethan Hawke) of a rural church asked by a congregant (Amanda Seyfried) to counsel her troubled husband (Philip Ettinger), an environmental activist who has started to think about becoming militant and dangerous.

And yet the movie, for all of Schrader's attempts to control its breathing, to hold things in reserve, becomes unexpectedly propulsive. If the voice of God is to be heard in this spiritual endeavor, you expect it to say, "Are you talking to me?"

"Yeah," said Schrader, laughing, "I didn't set out to create that kind of thing at all. But I'm in the editing room with the editor, and he turns to me and says, 'You know, there's a lot of Taxi Driver in this movie.' "

Taxi Driver, for the uninitiated, is the 1976 Martin Scorsese film starring Robert De Niro as Travis Bickle, a man going unhinged in 1970s New York as his obsession with a young prostitute (Jodie Foster) builds to a violent climax.

That hasn't much to do, on the surface, with the story of a small-town pastor tending to his flock, but both the De Niro and Hawke characters are tormented loners, and the specter of violence looms over both.

Those close to Schrader were the first to give him the unexpected news: His transcendental movie was actually kind of exciting.

"The first time I showed this film to my friends, I said you have to be prepared because this is very slow movie. And they're watching and saying, 'What are you talking about? This is not a slow movie,' " he said. "You actually want a bad screening, because the bad screenings are the ones that teach you the most about the movie. But we never had one."

The thing is, in terms of tempo, the movie is measured and slow to unfold by today's filmmaking metrics. But there is so much tension beneath the surface, pressure building to what we sense may be a violent eruption, that the movie, despite Schrader's best efforts, starts to play like a thriller.

"I was putting together all of these elements of slow movies, of the transcendental style, but I came to realize that the glue that was holding all of it together was Taxi Driver," he said.

That is, if Travis Bickle were a seminarian. One of the attributes that makes Schrader unique as a writer-director — he also wrote The Last Temptation of Christ — is his background as a theologian, including a degree from Calvin College and a strict Calvinist upbringing. He's very comfortable talking, for instance, about St. Augustine's ideas on martyrdom as they relate to the actions of Samson at the Temple of Dagon, and skilled at infusing those ideas and themes into a movie like First Reformed.

Once introduced, the actions taken in the name of religious extremism become part of the ticking clock that starts pounding as the movie builds to its conclusion.

"There's an early scene with [Ettinger], where he asks, 'Do you believe in martyrdom?' And all of a sudden it's on the table, and once that question is out there, it's out there, and it starts to inform everything that happens in the movie," he said.

I asked him, in retrospect, if his accidental Taxi Driver meets the requirements of transcendental filmmaking.

"That may be a little presumptuous, but I certainly tried to employ the techniques for the first time," he said.

Now that his turning-70 "life decision" has been addressed, what next?

"Now," he said, "I'm going to take a nap."