The search for the meaning of it all is perhaps the defining feat of humankind and certainly an endlessly ripe subject for the cinema.

It is not, however, the most intuitive essence one might expect of a documentary about Brit Russell Brand, the one-time ribald comic and actor and former husband of Katy Perry, who has transformed himself in recent years into an activist leading the charge for a social revolution.

"Russell Brand: A Second Coming," Ondi Timoner's documentary about the second act in the life of the "Forgetting Sarah Marshall" star, is all about his desire to make sense of the confusing and tumultuous whirlwind of everyday existence.

The film offers a chronological portrait of Brand's rise from being the lonely child of divorce through his early punk comedy days in Britain, a dire drug addiction, his subsequent explosion onto the mainstream, and retreat from Hollywood glamour into an endless battle against entrenched societal interests.

Brand's a fascinating, elusive subject and the same charisma that garnered him so much attention after his MTV hosting stints and movie appearances is well on display as Timoner captures him arguing with the press, visiting Occupy Wall Street and engaged in other protests against the system.

It's certainly a rare thing to see a celebrity turn so resolutely against the infrastructure that brought him fame and fortune. But Timoner has taken on a massive challenge in making this picture, faced with a subject who is so discombobulated in who and what he's railing against that the movie is more exhausting than illuminating. He's hard to keep up with, and frankly hard to take for 100 minutes. Brand is indisputably well-intentioned, advocating against income inequality and drawing on his own past to push for the decriminalization of drugs, for example, but you can vividly see why he's not the ideal vessel for these messages.