The documentaries of Errol Morris have always dealt, to some degree of another, with self-delusion, from “The Thin Blue Line,” which challenged the certitude of law enforcement types about catching the man who’d killed a cop, to “Tabloid,” about a woman who kidnapped a man she was sure was in love with her. But his most recent work has involved not only individuals, but the national self-deception involved in assuring ourselves of our rectitude in war.

That broader issue was certainly involved in “Standing Operating Procedure,” which traced the reality of the action of Americans at Abu Ghraib in a way that suggested we are all complicit in their activities, however much we (like the Bush Administration) tried to heap the blame on the guards alone. And it was certainly present in “The Fog of War,” in which former Defense chief Robert McNamara addressed his own responsibility in the debacle of Vietnam and the lessons that might be learned from that misadventure. (That film won an Oscar, of course.)

On the surface “The Unknown Known,” which presents a series of excerpts with former Bush Administration Defense Secretary Donald Rumsfeld embellished with archival autobiographical material, characteristically haunting imagery (mostly roiling waves or reference to Rumsfeld’s “snowflakes,” his many memos) and insistent music (this time by Danny Elfman), is merely a sort of companion piece to “The Fog of War.” Rumsfeld sits seated before Morris’ patented “interrotron” camera, which uses mirrors to allow him to be filmed looking directly at the audience while maintaining eye contact with the filmmaker. And he responds to questions, just as McNamara did. But the resultant portrait is very dissimilar. McNamara was reflective, regretful, apologetic. By contrast Rumsfeld is pugnacious, averse to self-doubt or even self-examination—and unwilling to admit even contradictions in the historical record.

Perhaps the difference lies in the fact that McNamara was chronologically much more removed from the catastrophic events he had been instrumental in creating, or in the two men’s varied backgrounds. McNamara was trained as a mathematician and statistical analyst, and he brings the rigor associated with those skills to looking back on his life. Rumsfeld, by contrast, is homo politicus, who began his career as a congressional staffer before becoming a young congressman from Illinois in the 1960s. During the Nixon administration he served in a variety of appointed posts before becoming Gerald Ford’s chief of staff and Defense Secretary. After Ford’s defeat in 1976, Rumsfeld entered the private sector, but under Ronald Reagan he served as a special presidential envoy to the Middle East (famously visiting at one point with Saddam Hussein), as well as in other semi-official capacities. But he appears to have learned very few lessons from those responsibilities; after George W. Bush was elected in 2000, Rumsfeld returned, at the suggestion of his old friend Dick Cheney, as Secretary of Defense, only to preside over the wars in Afghanistan and Iraq until Bush replaced him in 2006.

Throughout his discussion of his life, Rumsfeld maintains an attitude of coolly cheerful denial of any mistakes or regrets. Even when he alludes to old grudges—like what sounds very much like turf wars he engaged in with George H.W. Bush during the Ford years and Condoleeza Rice in those of the second Bush—he does so with the same semi-sarcastic grin he brings to his responses to questions about the use of “enhanced interrogation techniques.” His humanity can be glimpsed in his reminiscences of proposing to his wife and his reactions to 9/11 and Abu Ghraib, but even in these instances his defensive crouch is one designed to reject any hint of culpability while trumpeting his own sense of duty (as in his offers to resign over Abu Ghraib). When confronted by the infamous “torture memos” from the Department of Justice, he actually claims never to have read them. He’s no lawyer, he argues; what could he have brought to the table? When asked about the spurious Iraqi WMDs, he retreats into his famous dictum that absence of evidence is not evidence of absence—and suggests that Colin Powell knew exactly what he was about in his infamous speech before the U.N. When challenged about suggesting that Saddam Hussein was involved in 9/11, he both denies it and then covers himself with a joke about generalizations.

What emerges in “The Unknown Known” is a portrait of a man who’s not so much opaque as impervious—one so convinced that he’s right that nothing can dissuade him from what he believes; it’s literally impossible for him to seriously consider any alternative, even in hindsight. Rumsfeld comes across as a smugly smiling carnivore who’s happy to figuratively chalk up points against his interlocutor just as he joyously eviscerated—at least in his own mind—any journalist who had the temerity to ask him a challenging question during his Pentagon press briefings. Even when asked why he agreed to be interviewed by Morris, he sidesteps the question—a political creature to the very end. He seems to think that any time in the limelight will be beneficial, even though he must know that Morris will have the final say through his well-honed editing skills.

Rumsfeld ultimately comes across as a man who’s frightening in his utter inability to reflect on events in which he played a significant, if not totally determinative, role as well as their destructive impact upon the country and the globe—another portrait in Morris’ extraordinary gallery of self-deluding subjects, one more famous than the others.