The unthinkable (or unknowable?) has happened. Errol Morris has made a boring movie. And it's sort of not his fault. Who would have imagined that a series of interviews, conducted by one of the cinema's most incisive documentarians on one of world politics' most influential - and abhorrent, from certain perspectives - figures would be so unenlightening? The image is one of steely greys, a polished sight not of humble, austere truth and fact, but of the facade of that. It's too preened to be believed, literally, and so too is Donald Rumsfeld. His is a performance for the ages, so meticulously constructed is it, yet its impact is negated by that very thing - it's so meticulously constructed, it's obviously a lie. The Unknown Known is like watching a man on a screen tell you what he wants to tell you for 100 minutes, and believing none of it. In fact, that's entirely what it is. It'd be a fascinating reversal of fortune to see Rumsfeld hoodwink a man so astute and so knowledgeable as Morris, were it not for how little Morris seems to care. He presents Rumsfeld's sycophantic pontifications as reality, since they're largely the version of reality we have been fed over the decades, and treats his self-satisfied droning over history as sensational, groundbreaking testimony, when it's mostly just confirmation of what we already know. The film's most persuasive emotional pangs come as Morris turns to footage of Rumsfeld while in office in the Bush administration, addressing the press with an arsenal of callous hyperbole and terrifying ignorance that many of us had even identified then. Time has verified the truth, but has seemingly forgotten his lies. Rumsfeld sees the failure of Barack Obama to reverse many of Bush's most repulsive legislations as an endorsement of their potency. We see it as an endorsement of the everlasting power of evil. Did Morris not probe further on these matters? Or was Rumsfeld as calculatingly cold on them as he is on the few similarly difficult issues that he is faced with here? When he claims to not know even why he's taking part in this film, he lies again. And all generalisations are false.