EDWARD Norton is well-known for picking thought-provoking roles.
He's played a reformed neo-Nazi in American History X; a leper king in Kingdom Of Heaven - and the famous green giant known as the Incredible Hulk. Oh, and let's not forget his turn as a singing purple rhinoceros in 2002's Death To Smoochy.
"I guess it's fair to say that every actor likes the idea of complexity in a character," Edward explains when asked about his career choices.
"I think we're all trying to find something meaty to work with, or frankly, something that is hard. You get into this [acting] because you want to pin down things that are complicated or hard about people.
"On some level, I just think people are paradoxical. I think ultimately everybody's grey, I don't think anybody's easily reducible. But I like any character that's got contradictory impulses or shades of ambiguity about them. It's fun because it's hard."
The 39-year-old's next role sees him playing Ray Tierney, a New York policeman, in new film Pride And Glory. Edward co-produced the film, which also stars Colin Farrell.
"You learn more about him [Ray] from the things other people say about him than the things he says for a long time, and it's just very mysterious," he explains.
"I found myself reading along and wondering what the deal was with this guy. That's unusual in a script because a lot of times, people will telegraph and make sure you understand the character. To leave a lot of empty space in a character was kind of interesting on a writing level because you end up reading it. That was a particular thing that interested me with this one."
As he questions the morals of those around him, Ray has to decide where his loyalties lie - with his family, or with the institution. Edward says he thinks this gives the film particular relevance.
"I looked at it and I thought, this has questions in it," he reveals.
"This is questioning dynamics that our whole country is going through right now and maybe that makes it special to our moment. It's fun to play cops and robbers but I started to have a special interest in it when I thought this could actually be something that's reflecting the moment we're going through in terms of what the US as a culture is going through, its own sense of the ethics."
"The more I looked at the script and looked around at what was going on, the more I felt like it was starting to have an extra resonance for me because on some levels, it's about the difficulty of speaking truth to power and the tensions between our loyalties to the people who do this service for us and the need to hold them to a higher standard in terms of the principles.
"And so, all of a sudden, this cop drama had the potential to resonate on things that were going on in the zeitgeist. That's something that always makes me happy."
While he's used to roles that take him out of his comfort zone, he says it was a challenge to play a cop.
"We've always made heroes out of guys who put the badge on, and the insulation between chaos and everybody else," he says.
"I definitely think we've got a hero myth and relationship with those people who put the badge on and defend everybody else."
The Oscar-nominated actor is also renowned for his work behind the camera. He made his directorial debut in 2000's Keeping The Faith, and is set to direct upcoming film Motherless Brooklyn, as well as an untitled documentary about American president-elect Barack Obama, which he admits he can't discuss.
"It's something I can't talk about that much just because we have a relationship with them," he says.
"We're making a historical record, not something to play a role in the election, so we have an agreement that this is something that we won't talk a lot about or really publicise until the election's over. So I can't really comment on our access because it's part of our arrangement with the campaign. But it's a fascinating thing to be able to be documenting."
While he's a reluctant celebrity, Edward - who has been engaged to Courtney Love and Salma Hayek - prefers to use his star status to draw attention to social and environmental issues. He is a member of the board of trustees of the Enterprise Foundation, which develops affordable housing, and supports BP's Solar Neighbours programme.
"It's a nice position to be in; I'm lucky," he says of his fame.
"At the same time, all the excitement of that has been put into stark perspective. In some ways, the highs of it have been blunted, which in a way, is a gift."