During the first few seconds of David O. Russell's "I Heart Huckabees," a voiceover of Jason Schwartzman spits profanities at the meaninglessness of his existence, and I couldn't help but smile.

Some 100 odd minutes later, as the credits rolled, that not-quite stoned/not-quite contemplative smile remained intact.

For a writer-director already lauded for risky material ("Three Kings," "Flirting with Disaster" and Freudian-bent "Spanking the Monkey"), this is his riskiest film to date: a whimsical, circus-like endeavor that tingles the senses and heartstrings despite its absurdity.

Billed as an "existential comedy," the film gives a Cliffs Notes version of philosophical discourse, juxtaposing notions of nihilism and mankind's collective experience while equally brushing over topics like oil and land conservation, Americana and love.

Unlike, say, Richard Linklater's "Waking Life," "Huckabees" stays well enough plot-oriented, and downright entertaining — to avoid simply exercising one's right to document philo-babble.

Schwartzman plays Albert Markovski, an environmentalist activist who hires two "existential detectives" — Lily Tomlin and Dustin Hoffman — to spy on him with hope of finding out what life means and where he fits into it.

Seemingly void of Albert's befuddlement is a stylish, confident Jude Law, rising go-getter at Huckabees — a Sam's Club/Target-type conglomerate — who courts the company's flighty, eye-candy of a cover girl Naomi Watts.

Best of the bunch is Mark Wahlberg's Tommy Corn, a hilariously childish fireman who's longing for the same philosophical solace as Albert, thus taking an immediate liking to him.

It wouldn't be surprising if Russell wrote the script — along with writing partner Jeff Baena — with Wahlberg and Schwartzman's previously uncontested acting accomplishments in mind.

Schwartzman displays the idealistic, love-struck misanthropy that perfectly suited him to lead Wes Anderson's "Rushmore." Interestingly, Albert writes terrible poetry to get across his ideas while "Rushmore's" Max Fischer puts on shoddy, crowd-pleasing plays. Similarly, Wahlberg balances testosterone-driven outbursts with simple-minded reflections as seen with "Boogie Nights'" Dirk Diggler.

Russell's not role swapping. He's too smart and, judging from the film's context, probably too self-conscious for anything like that.

Bouncing off one another like a high-scoring pinball game, characters run into occasional cathartic moments. More often than not, though, the film's willful to complicate an already confusing premise, which works just fine.

"Huckabees" plays around the hard-hitting questions too many films today neatly wrap up, and meanders gleefully between the outrageous and oddly touching.

It's self-inflicted hysteria, an original addition to the American comedy, and remarkably propelled.

Grade: AB