“Have you ever seen a man’s brains?” That question is asked by one of several old eccentrics who populate Vernon, Florida, the town after which Errol Morris named his second documentary feature in 1981. It is a question that has been at the heart of just about every film Morris has made; he seems fascinated, even haunted, by the question of how the mind works. He explored that theme in his recent docu-poem Fast, Cheap & Out of Control (1997). It also provides the key to what seems at first like a meandering digression in Morris’s most celebrated film, The Thin Blue Line (1988). Near the end of that documentary, about an innocent man who was sent to prison and almost executed for a murder he didn’t commit, Morris lets another man, David Harris, talk about his own childhood. It was Harris’s accusations that prompted the police to arrest the innocent man in the first place; now that Harris himself is on death row for another murder, he all but admits to Morris that he committed the original crime himself. For most viewers, the case is closed, the story told. Yet Morris lets Harris go on and trace his reckless behavior back to his youth. “I wasn’t doing nothing but hurting myself,” Harris concludes.