The title of "An Unreasonable Man,"Henriette Mantel and Steve Skrovan's improbably riveting portrait of Ralph Nader, is from George Bernard Shaw, who wrote: "The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man."

That the filmmakers have chosen that quote as the film's opening epigram speaks volumes about their perspective on Nader, who for millions of Democrats immolated a heroic legacy of consumer activism and advocacy by running for president in 2000 and, by their lights, contributing to the election of President Bush.

That issue is tackled head-on at the top of "An Unreasonable Man" and sets up the narrative tension of a film that then doubles back to document Nader's epic battle with General Motors in the 1960s and the juggernaut of consumer consciousness and policy shifts he so effectively piloted thereafter. Using a combination of archival footage and talking heads (former Nader's Raiders, supportive and disgruntled), they also chronicle how Nader came to make that quixotic 2000 run.

Nader haters may not be mollified, but "An Unreasonable Man," like its subject itself, is a one-stop civics lesson no one should miss.

-- Ann Hornaday

An Unreasonable Man Unrated, 122 minutes

Contains three swear words (none of them by Nader). At Landmark's E Street Cinema.