"The Unknown Known" finds Academy Award winner Errol Morris gifted with a juicy subject: Donald Rumsfeld.

The movie represents an attempt to understand an important chapter of history from the perspective of one of its most prominent observers, blending stark HD interviews with stock footage, stills and scenes of Rumsfeld reading from some of his thousands of memos.

The filmmaker finds the former Secretary of Defense singularly convinced of his righteousness and utterly free of guilt and self-doubt even when it comes to discussing the Bush administration's many missteps.

This is less of a face-to-face interrogation than a gentle probing. Morris is often inclined to illuminate Rumsfeld's apparent misstatements and half-truths by showing past C-SPAN broadcasts rather than calling things out to his face. But make no mistake, by stressing Rumsfeld's propensity for gibberish and casual dismissals of great suffering, the picture amounts to one grand show of self-incrimination.