Unlike most recent documentaries, "An Unreasonable Man" doesn't just preach to the choir.

The film is sympathetic to the unreasonable man in question, Ralph Nader (it was directed by a former staffer who still admires him), but it's surprisingly even-handed. "Unreasonable," mostly talking heads with a little playful narration tossed in to make it seem less talking-heady, probably gives us more detractors than supporters.

"He's a psychologically troubled man," says writer Eric Alterman, who also calls Nader "wicked." Alterman is referring to Nader's runs for the presidency in 2000 and, especially, 2004, when even such Naderphiles as Michael Moore begged him not to drain support from John Kerry. The conventional wisdom - and it's wisdom that "Unreasonable" doesn't do much to dispel - is that, for good or ill, Nader's presidential campaigns guaranteed two wins for George Bush the Younger.

"Unreasonable" backtracks to show Nader's saintly early years, when he fought for consumer safety. But it picks up steam when it gets to the presidential campaigns and the debate about whether Nader's unusually large head corresponds to an outsized ego or whether he believed his campaigns were worthwhile.

There's something to be said for both views, but the most persuasive argument in "Unreasonable" has nothing to do with whether Nader is presidential and everything to do with the things he might have been paying attention to if he hadn't been distracted by the Oval Office: Enron, WorldCom, sweatshops and globalization.

What: "An Unreasonable Man"

Directed by: Henriette Mantel and Steve Skrovan

Rated: Not rated, but contains strong language

Should you go? Yes. It could make you question your convictions instead of simply confirming them. ***