Errol Morris is the legendary documentary filmmaker who won an Oscar for The Fog of War, featuring Robert McNamara and his regrets about the war in Vietnam. His new film, The Unknown Known, is based on thirty-three hours of interviews with Donald Rumsfeld, secretary of defense under George W. Bush. This interview has been edited and condensed.

Jon Wiener: Donald Rumsfeld grins a lot in this movie. The most memorable thing about this film is his grin. What do you make of it?

Errol Morris: Supreme self-satisfaction. Cluelessness. Inability to deal with the reality of what he’s done.

JW: When you asked him about the lessons of Vietnam, he says the lesson is “Some things work out; some things don’t. That didn’t.” What do you make of that?

EM: To me, it’s a non-answer. But it also may reveal a lack of insight that characterizes almost all of his responses.

JW: You’ve read thousands of his memos. Is there one you consider the most problematic?

EM: Telling the president during the pre-war search for WMD that “absence of evidence is not evidence of absence.” It’s saying in effect, “Disregard the evidence. Disregard the fact that UN weapons inspectors have been all over Iraq and have found nothing. Just because you have evidence of absence, let’s pretend we have evidence of nothing, and go to war anyway.”

JW: Donald Rumsfeld is impressed by his own aphorisms, especially that business about “the unknown known”—“things you think you know that it turns out you did not.” But when you talk to him about this, he gets it wrong. He says it means “things you think you do not know that, in fact, you do.” You point out with some exasperation that that’s the opposite of what he originally said. What does this suggest about him?

EM: Here’s a man who can say contradictory things in the same sentence and not even realize it. The first of those statements is humble: I could turn out to be wrong. On further reflection, he decides he likes a different version: we actually know more than we think we know. Maybe we know everything! Maybe we don’t have to listen to anybody.

JW: When you ask him about the torture memos, he says, “I’ve never read them.” Do you think that’s true?

EM: The horrifying thing: yes, I do. It would be a much kinder story about him if he was lying. But I think he didn’t care enough to actually read the material.

JW: There is one moment in the film where he chokes up as he describes visiting a wounded soldier and his family at Walter Reed medical center—what did you make of that?

EM: Donald Rumsfeld is not crying about the war; it’s about the one soldier who miraculously recovers. It’s almost as if death is not part of this equation, and like everything else, he can put it out of his mind.

JW: When he’s being evasive, when he’s taking so much pleasure in his deceptive phrases, do you think he’s deliberately lying?

EM: This is the question at the heart of the movie. Is he self-deceived? Is he clueless? Does he not understand the import of the questions? I came to believe there was not much there. He is not stonewalling or sidestepping; he is revealing something about how he sees the world. In my view, it’s horrific.

JW: How did you get him to do this interview?

EM: I asked him, and he said yes. In many ways, I am an honest broker. I’m a person willing to sit there and listen. I was polite; he was polite. He gave me a lot of time. He gave me access to his memos. He was unfailingly cooperative, charming, even likable. But in the end, he saw me as just one more press conference.

JW: Thirty-three hours is a long press conference. How did you stand it?

EM: Near the end, I feared that it might be doing neurological damage. But it’s over, and I’m just fine.