There is no more thoughtful nonfiction filmmaker in America than Errol Morris. The son of a doctor and a musician, Morris left New York to study history at the University of Wisconsin and philosophy at Berkeley, falling in love with movies at the Pacific Film Archive. His 1988 exposé "The Thin Blue Line," in which he investigated a Texas murder case with his camera, led to a death-row convict's sentence being overturned.

Morris has made quizzical documentaries about a pet cemetery (1978's "Gates of Heaven") and physicist Stephen Hawking ("A Brief History of Time," 1992). He won an Oscar for "The Fog of War," his 2003 film about Robert McNamara, the U.S. secretary of defense in the early years of the Vietnam War. His latest, "The Unknown Known," profiles Donald Rumsfeld, secretary of defense at the end of Vietnam and again at the start of the Iraq war.

"You can't call this 'The Fog of War 2,' " Morris said in a recent phone conversation. "I can't imagine two individuals more unalike. If you want another movie to compare this with, pick 'Tabloid,' " where Morris revisited an absurdly convoluted 1970s sex scandal and its dissembling femme fatale, madly convinced of her innocence and convincingly mad. "Another self-deceived, delusional character totally out of touch with reality," Morris said.

Morris believes Rumsfeld cooperated because he relishes outfoxing interviewers. He built up a considerable fan base for his TV news conferences where he dueled with reporters. The film would allow him to enjoy that feeling again.

"He liked being in front of the cameras, he liked being in a position of power. He really came into his own during these news conferences in the run-up to the war in Iraq. His approval ratings shot sky-high. People were charmed, delighted. Then his precipitous fall from popularity to his disgraced departure from the Defense Department six years later."

Documentarians should debunk an unreliable source, Morris said, but also give him a reasonable chance to make his case.

"I believe in contextualizing. Where I felt I had to, I show that he is saying something utterly untrue. If he says that no one in America was confused about a possible connection between Saddam and Osama, I show him saying the exact opposite in a news conference. If he says that his torture policies never migrated from Guantanamo to Iraq, I read him a report by former Secretary of Defense James Schlesinger that says exactly the opposite.

"What's really interesting, and this is ultimately what the film is about, is when he's contradicted, when he is shown to be wrong, how he reacts, how he deals with that fact. You know how he reacts? He pretends as though it never happened."

While the movie never turns into an anti-Rumsfeld editorial, it became, Morris said, an inquiry into "whether he even knows he's lying. Denial. Cluelessness. Glibness. Arrogance. And this is the guy we've entrusted the lives of our servicemen to? What a portrait."

Colin Covert 612-673-7186