When he renounced possessions, friends and family in 1990, Chris McCandless, 23, was an intense and idealistic college grad fleeing the savage materialism of so-called civilization. He took his savings, gave it to OxFam, and hit the road.

A self-styled monk whose hermitage was the American outdoors, McCandless sought serenity in rugged mountains where he mastered his fears, and on the sparkling rivers where he rode the rapids of self-reliance.

On the basis of the exhilarating Into the Wild, Sean Penn's exceptional film inspired by Jon Krakauer's nonfiction best seller, McCandless (charismatic Emile Hirsch) found what he was looking for.

And also something that he wasn't: his demise.

As Penn tells it in this exalted American Odyssey that can be read as spiritual pilgrimage, cautionary tale - or both - the most rugged landscape he encountered was psychological, not physical. As he one-mindedly chased autonomy, McCandless was running away from his parents.

He repudiated the family name, rechristening himself "Alexander Supertramp," before embarking on his journey. It would take him up to the Dakotas, down to Baja California and, finally, to his ultimate destination, the Denali National Park near Mount McKinley in Alaska, where he set up camp in an abandoned school bus.

As actor and director, Penn long has been drawn to the existential and elemental. Life and death (Dead Man Walking, Mystic River). Remorse and revenge (The Crossing Guard, The Pledge). All these themes converge - symphonically - in Into the Wild, his most fully realized work as a director. And curiously, his most exuberant.

Penn immerses the audience in the majesty of the deserts, mountains and waterways, which have their counterpart in each American soul. His collaborator, cinematographer Eric Gautier, frames each vista as though Chris was the first explorer to make landfall.

It is tempting to compare Gautier's previous film, Walter Salles' The Motorcycle Diaries, about the young Che Guevara and his medical-school companion journeying through South America, with Penn's dramatization of McCandless' journey of self-discovery. Where The Motorcycle Diaries was a unification story of a continent, Into the Wild is a study in individualism.

Penn sees McCandless, who had his reasons to reject his family, as a damaged soul hungering for the parenting he never received.

Along his journey he encounters surrogate mothers and fathers - hippie chick Catherine Keener and military man Hal Holbrook - with whom he briefly opens up before escaping the bonds of human connection. In a brief soliloquy that is the heart of this heartfelt film, Holbrook is transcendently moving.

So is Hirsch throughout. The affable young star begins the film buff and robust, ready to meet the challenge of the outdoors, and ends emaciated, a prisoner of his failing body, underlining the film's journey into self.

The plaintive ballads by Pearl Jam's Eddie Vedder on the soundtrack do little to enhance the film. They are the only misstep in Penn's otherwise sure-footed journey to what he reveals as the heart of lightness.

Into the Wild ***1/2 (out of four stars)

Written and directed by Sean Penn, based on the nonfiction account by Jon Krakauer. With Emile Hirsch, Catherine Keener, Hal Holbrook, Kristen Stewart, Jena Malone, Marcia Gay Harden and William Hurt. Distributed by Paramount Vantage.

Running time: 2 hours, 20 mins. Parent's guide: R (brief nudity, profanity, mature themes)

Playing at: Ritz Five, Showcase at the Ritz/NJEndText

Contact movie critic Carrie Rickey at 215-854-5402 or crickey@phillynews.com. Read her blog, "Flickgrrl," at http://go.philly.com/flickgrrl/