MICHAEL MOORE IS AT the top of his game. Audiences have made his latest project, Sicko, the fourth most successful documentary ever released. Critics are calling it his most impressive work yet. And he's basking in the life-giving glow of TV lights while calling his interviewers tools of Big Pharma. And yet, Sicko is the work of an artist in a deepening creative funk.

Whatever else one thinks of him, the idea of Michael Moore as stunted doesn't come naturally. Beginning with Roger & Me, he's single-handedly refined a style of documentary film--call it Moore style-that has changed the genre. Moore is fundamentally two artists--one a polemicist, one a comedian--and his style is split, too. The foundation is always a standard left-wing argument. The real life of his work, though, is his inimitable humor: wry montage, deadpan narrative, slick editing, stunts out of a socio-political Jackass and interviews that make powerful people visibly uncomfortable. The effect is pure ying-yang. The passion gives his nonfiction frolics direction and speed. Moore's inner jester lightens his films' tendency toward insufferable preaching. And the ambiguity between them leave it unclear why audiences respond to Moore's work. Are they snickering or pounding their fists on the armrests? Or both?

Whichever, the style made him the richest, most influential documentary-maker of all time. But it predisposes him, perhaps more than most, to that quandry all worthwhile artists eventually wrestle with. No matter how technically proficient, they want to see their work actually accomplish something. And a decade-plus of

The original idea for Sicko came to him from his short-lived TV series The Awful Truth. In one segment he found a man whose HMO had denied him a potenitally life saving pancreas transplant. Moore showed up at the company headquarters, did his by now familiar routine, and the man got a pancreas.

"One of the original ideas I had for this movie . . . was that I was going to do that 10 times. Ten 10-minute segments. And we could do that and save 10 lives," Moore told Entertainment Weekly. "[But] what did that accomplish? . . . There's much bigger fish to fry here than going after one little board . . . I guess that would make a good film, but everyone would go, 'There goes Mike again' . . . That's good. But I hope to see a larger change in the not-too-distant future . . . [ultimately] I felt it would be much stronger not to have me in the way."

So Moore's mischievous smirk--present on every promo poster, DVD cover, and nearly every frame of every Michael Moore documentary--hangs back for the first 40 minutes of Sicko. Gone are the cloying cartoons, the ambush interviews, the playful stuntifying. Where the absence of Moore's foolery leaves space for profiles of people who died because their insurance companies wouldn't foot the bill, Sicko is moving. And critics have hailed the new, more reflective Moore. But they might have added less entertaining.