A hefty biography of the 17th-century German mathematician and astronomer Johannes Kepler sits on the dining room table at the house John Hancock is renting just north of Broad Street. Hancock, a baritone, is in town to prepare for the lead role in a Philip Glass opera about Kepler, and while he’s mastered the music, he’s still exploring what sort of a man Kepler was.

“There’s a couple others that are a little bit sexier,” he says, nodding toward the 1948 tome by Max Caspar, a 400-plus-page read that is nonetheless considered the definitive life story of the man. Kepler, a contemporary of Galileo Galilei who is best known for his laws of planetary motion, spent much of his life dealing with pressures from the Catholic and Lutheran churches (he was a member of the latter), all the while reconciling religious faith and scientific reason in his own mind.

Kepler, the opera, premiered in 2009 in Linz, Austria, a city where Kepler spent several years teaching and studying, and it later had a U.S. premiere as a concert-only performance in Brooklyn. This is Hancock’s first Glass opera, although he has been fascinated by the composer’s work since hearing his soundtrack to the dialogue-less 1982 film Koyaanisqatsi as a teenager growing up in New York City. Glass has been called a minimalist for the repetitions and arpeggios in his work, but he has distanced himself from the minimalist movement.

Hancock, who speaks in a dry, Ray Romano-New York cadence, calls the minimalist label “a boring term.” In this role, he says, his vocal line often moves independently of what’s happening in the orchestra, “yet it all melds together quite seamlessly.” Hancock last came to Charleston in 2007 to play the lead in Pascal Dusapin’s Faustus, The Last Night, a complex vocal role that he describes as “musically backbreaking.” In the Kepler role, he chose to learn straight from the musical score rather than consult earlier recorded performances. “The thing is to try to invest this with as much emotion as possible,” he says.

The libretto of Kepler draws heavily from English translations of Kepler’s own writings, making for an opera that is, on its surface, far less dramatic than most. For one thing, there is no discernible narrative; this is a work about the life of the mind.

It’s an interesting move on Glass’ part, Hancock says, especially given the level of intrigue and drama in the scientist’s personal life. Kepler’s wife died of Hungarian spotted fever; his son died of smallpox; the religious turmoil of the time frequently forced him to bounce from one university to the next; and he had to hire a lawyer to defend his 70-year-old mother against accusations of witchcraft. In the biographies, Kepler is “constantly getting on his horse and riding across Central Europe to save his mother or find something out,” Hancock says.

“You could totally make a medieval European action-adventure story out of the life of Kepler if you wanted to,” he adds, but the opera only touches on the man’s personal life tangentially.

In a review of the November 2009 Brooklyn performance, New York Times critic Allan Kozinn makes note of the drier moments in the production — for instance, when Kepler walks through the steps of the scientific method to ponder what gives snow its starry shape — and writes, “chills do not run up your spine.”

Singing a few selections in the lobby of his house, Hancock picks just that moment to share in song: “Now I wonder/Does the cold/Cause the structure of snow?” In Glass’ treatment, the words take on the character of a meditation or a chant, as does the musing, “Where does the shape of snail shells come from?” In his research for the role, Hancock has discovered that these esoteric pages from Kepler’s notebook come from a year when the scientist allowed his mind to alight on such topics as the shape of pea pods and pomegranates. It was an “intellectually fluffy” time for Kepler, Hancock says, but one that can be universally appreciated.

“We’ve all had those moments of thinking, ‘Who made this work this way?'” Hancock says. “I think it’s actually sort of a shame for the reviewer not to allow himself to sink into that moment that all humans enjoy … We live in a time when rational thought is thought to trump the notion of what is divine, and the thing is: Are they mutually exclusive? No, I don’t think they are.”

It will be for the audience to decide whether Kepler works as a commentary on the modern culture war between people who see religious faith and modern science as irreconcilable, but Glass has certainly not been shy in making political statements with his art. In December, he stood with Occupy Wall Street protesters outside a Lincoln Center performance of his own opera about the life of Mohandas Gandhi, Satyagraha, and recited the closing lines of the opera, drawn from the Bhagavad Gita. With the crowd echoing him in the occupiers’ signature call-and-response human microphone, he spoke of “thrusting back evil and setting virtue on her seat again.”

Kepler is the only named character in the opera, and Hancock sees the six other vocalists as functioning like a classical Greek chorus. Sometimes they pose questions that, combined with the hypnotic sounds coming from the orchestra, suggest a man in turmoil. “Ultimately, he really just wants to peacefully be able to study,” Hancock says.