Documentaries raise more questions than any other branch of filmmaking about what it means to be an active part of the world at the same time as you record and represent the world on screen.
"Stevie," a nonfiction film by Steve James, raises such questions so vividly that they become an integral part of the movie itself, as interesting as the people and events Mr. James has chosen for his subjects.
While going to college in the Midwest during the 1980s, James joined a charitable organization and served as "big brother" to an 11-year-old named Stevie Fielding, who was troubled by personal and family problems.
After moving away and getting on with other aspects of his life, James paid a visit to Stevie about 10 years later, and was unhappy to discover his friend had been faring badly, feuding with relatives and getting arrested for numerous crimes.
Wishing to understand Stevie's problems better - and feeling guilty over the shortfall of his own mentoring - James decided to stay near Stevie for a while and make him the subject of a film.
James was well equipped to do this, as his 1994 documentary "Hoop Dreams" had earned an Oscar nomination for its account of poor African-American boys hoping for glory on the basketball court.
What happened next became a focal point of his movie-in-progress: Stevie was arrested for sexually abusing a little girl he was babysitting, touching off a long and painful encounter with the criminal-justice system.
James observes as much of this as possible through his camera - hoping his "little brother" won't suffer too much, yet recoiling from the enormity of the young man's crime.
On the surface, "Stevie" is a fascinating look at the life of a young man who seems in some ways almost freakish, in other ways all too typical of the uneducated working-class milieu he hails from.
Deeper down, "Stevie" is an introspective journey by James himself, who examines not only Stevie's terrible problems, but also his own complicity in those problems.
He feels his personal involvement in two ways: as a former mentor who failed to set his "little brother" onto productive pathways, and as a filmmaker who's trying to offer belated help and sympathy but is simultaneously profiting from - maybe even exploiting - the maladjusted young man by making a movie about him.
"Stevie" portrays a remarkable gallery of real-life characters, from Stevie's long-suffering relatives and hopeful fiancée to James's ambivalent wife, who supports her husband's work but can't bring herself to let Stevie spend a night in their home.
It's no accident that this movie is named after both the filmmaker and his subject. It stands with the most thoughtful releases of recent months, and will linger in memory.
• Not rated; contains candid discussion of sexual crime.