What Jackson loves most about acting, though, is the process, the satisfaction of taking the job seriously. “I was raised by my grandfather, a janitor,” he said. “As a boy, I went with him to clean offices. I learned a man gets up in the morning, he goes to work.” Before shooting, Jackson reads his script a dozen times, sometimes memorizing all the other characters’ lines as well as his own. Jackson is almost pathologically meticulous about hitting his mark, picking up a prop, say, on the same word, take after take. “That’s called playing the movie game,” he said.

And he expects the same level of professionalism from his colleagues. Scarlett Johansson, who worked with Jackson on “Iron Man II” and “The Avengers,” told me he can get angry “if someone doesn’t do his job correctly — he does not suffer fools.”

When Jackson was making a filmed version of the play “The Sunset Limited,” with Tommy Lee Jones, the play’s author, Cormac McCarthy, complained about his line readings. Jackson said: “It sounds better my way. I’m not trying to make this [expletive] worse!”

Before visiting with Jackson one night, I called his wife, LaTanya Richardson, who is also an actor. I told her I had a fascinating conversation with her husband. “Of course you did,” she said. “Sam loves to talk about himself.” Richardson met Jackson in Atlanta in the ’60s when he was a student at Morehouse and she was a student at Spelman. “Sam was not part of my circle,” she said. “I was a theater snob; he loved movies.” But she said they did get him to do plays at Spelman.

She described Atlanta of those days as a mecca for African-Americans demanding racial justice. Jackson would eventually become one of those angry revolutionaries, but when Richardson first met him, she said, “I never saw anger in Sam.” After a long courtship during which they dated others, Richardson decided it was time to marry either a rich boy or a smart boy. “I married the smart boy,” she said, and they’ve been together ever since. But it hasn’t been easy. She’s passionate and outspoken, and Jackson is, in her description, “emotionally disconnected.” When she would call him on a movie set and ask him if he missed her, he’d say no. “But he’s changing,” Richardson said. “The other day I cut my hand, and he took me to the hospital. Years ago, I’d have to go by myself.” There were long absences during which “I felt abandoned,” she said. “It was easier in the earlier years when we sometimes acted together onstage.” But when their daughter, Zoe, a freelance film and TV producer, was born 30 years ago, Richardson stopped working regularly, because, she said: “We’d vowed to be an intact revolutionary black family. But it was very, very hard.” After Richardson stopped traveling a lot, she served as her husband’s acting critic. She once told him that his acting was “bloodless,” that his meticulous preparation hid the fact that “he didn’t infuse his acting with anything that grabbed you.” She told me: “I was trying to help. He said I had no filter in me.” When I asked her the secret to their 40-year relationship, she said, “Amnesia.”

Jackson was born in Washington. He saw his father twice in his lifetime. Before he turned 1, his mother took him to Chattanooga, Tenn., where his grandparents and aunt lived, and returned by herself to Washington. For the next nine years, he saw his mother sporadically. His aunt, a performing-arts teacher, put him in her school plays beginning when he was a toddler. “She was the reason I became an actor,” Jackson said. She also helped cure his debilitating stutter by taking him to a speech therapist. “It manifests itself more when I read than when I talk,” he said. “I have no idea why. Denzel stuttered. James Earl Jones stuttered. There are still days when I have my n-n-n days or r-r-r days. I try to find another word.”

He grew up in a poor black neighborhood, “but everyone had shoes and food,” he said. There were “two white houses of prostitution” in the neighborhood, and three other houses sold moonshine, and a fourth belonged to a “P.W.T. family. Poor White Trash. Their house had no running water, so they only took baths when it rained. They called me nigger boy and my grandmother Miss Nigger. It was always ‘Miss,’ as if a term of respect. When my grandfather took me to work with him, the whites there would rub my head, affectionately. I’d [expletive] look ’em in the eye to make them uncomfortable. But it was nothing to be angry about. Segregation was just a way of life.”