Many of Errol Morris' documentaries prove the old adage that "truth is stranger than fiction." In A Brief History of Time, a paralyzed astrophysicist talks, through a computer, about how time will one day run backwards. In Mr. Death: The Rise and Fall of Fred A. Leuchter, Jr., a designer of more humane electric chairs is obsessed with proving that the Holocaust never happened.

Morris, who has a degree in philosophy and once worked as a private detective, has also made films about the difference between truth and fiction—particularly the fictions created by people in power. In The Thin Blue Line, Morris documents the conviction of an innocent man accused of killing a police officer in Dallas County (the man was retried and exonerated a year after the picture was released). He presents us with a picture of how, as one of the interviewees put it, "the wheels of justice got rolling in the wrong direction," and how those in charge of administering justice kept them rolling that way because they wanted a conviction more than they wanted the truth.

The subject of The Fog of War, Errol Morris' newest documentary, is Robert McNamara, former Secretary of Defense under Presidents Kennedy and Johnson, and arguably the chief architect and advocate of the Vietnam War.

Like The Thin Blue Line, McNamara's story is one of "wheels rolling in the wrong direction"—although not at first. As President of the Ford Motor Company in the mid-1950s, and well before Ralph Nader's campaigns for auto safety, McNamara introduces the seat-belt to the American car industry. Soon after, as an initially-reluctant Defense Secretary in the early years of the Kennedy Administration, he sides against the hawks during the Cuban Missile Crisis, and helps avert a nuclear war.

But then, a few years later, he almost single-handedly pilots the nation into the appalling and interminable carnage of Vietnam.

Which is the real McNamara?

Morris lets the man tell his own story in a series of interviews under the headings of eleven "lessons" drawn from McNamara's reflections on his own life: Rationality will not save us. Empathize with your enemy. Choose proportionality in war. Belief and seeing are often both wrong. Get the facts. Be ready to reexamine your reasoning.

What comes through is the picture of a man who takes an unusually critical view of his own life, and of the mistakes he made as a military leader—most of them with devastating consequences for tens of thousands of soldiers and hundreds of thousands of innocent civilians in the Vietnam War.

McNamara self-effacingly uses the phrase "the fog of war" to describe the feeling of making decisions based on "unreliable information" amidst the bewildering complexity of warfare. His metaphor calls to mind the trumpeter in War and Peace who determined the outcome of an entire battle simply by failing to blow his bugle at the right moment—an alarming little detail which reveals the deep folly of the "calculus" of war. After all, how can one justify a little evil for the sake of a good result if there is no way of knowing what the results of our decisions will be, so many of life's details lying outside our knowledge, let alone beyond our control ("Goddammit, where's that bugle??").

To his credit, McNamara wrestles with questions of jus in bello—of just conduct in war: Should there, he wonders aloud, be a rule against fire-bombing women and children in the middle of the night (as in the bombing of Tokyo)? He also agrees with General Curtis LeMay —the notoriously unflinching commander of the bombing campaigns against German and Japanese cities in World War II, under whom McNamara served during the war—that our military leaders in the Second World War, had they lost, would have been tried as war criminals.

At one point he declares: "I think the human race needs to think more about killing: How much evil must we do in order to do good?" This should be a rhetorical question (the answer being "None"). But unfortunately, McNamara seems insufficiently awed by his own imagery to give the right answer. He concludes that, while "proportionality" should govern such reasoning, doing evil that good may come of it may sometimes be necessary.

In the end, the image of McNamara that emerges is of a man who wants to confess something, but can't bring himself to look in the face the evil he's done.

Morris, apart from a few moments of impatient directness, allows McNamara to be McNamara. He lets him state his case, to speak his piece and make his quasi-confession, rather than put him on the defensive.

But at the same time Morris highlights what McNamara is not saying by overlaying archive film footage of war machinery and devastation throughout the interviews, and interspersing recordings of clandestine phone conversations between McNamara and Johnson.

Morris seems to be telling the audience that the horrific destruction of which McNamara speaks calls for more than mere admissions of error and philosophizing about misleading pre-conceptions; that the striking discrepancy between his private, behind-the-scenes despair when speaking to his President and his public optimism when speaking to the public about the "Vietnam situation" creates a tension that cries out for resolution.

Probably the most painful evidence of this tension, of McNamara's inability to confront his past, is that despite how forthcoming he has been throughout the interviews, when Morris asks him point-blank about guilt, he is weirdly, uncharacteristically evasive, and when he finds himself speaking about the effect that his role in the Vietnam War had on his family, he quickly changes the subject.

Yet the feeling I had at the end was that anyone in the audience who had been looking forward to hearing McNamara's mea culpa—and been disappointed—nevertheless would not have left the theater quite as angry at this man as before they entered. This was evidence enough for me that Morris, his visual commentary aside, had allowed the truth to speak for itself.

What was that truth? McNamara was a man divided, a man who consciously absorbed in his person the contradiction between his private anxiety and his public confidence, between his private dread and his public advocacy, all for one simple reason: He loved his President. He loved Lyndon Johnson like a son loves a father—loves him even if he suspects, or knows, that his father is not in the right. He loved him like Thomas More loved his King, even as he knew with certainty that his King was wrong.

Of course, the difference between More and McNamara was that More's love for his King did not lead him to do evil for his King's sake—a difference which reveals that what our "complex modern world" needs, perhaps more than anything else, is the simplicity of the martyr.