When you talk to Viggo Mortensen, he manages to go deep, fast. Nazi Germany, his family background, his struggle with his own prejudices, his approach to life -- it's all there in the first five minutes of our conversation. It's this sort of introspection that makes Mortensen's latest role in Good particularly compelling.

The film, based on the 1981 play by C.P. Taylor of the same name, tells the story of history professor John Halder who, through no desire of his own, is promoted up the ranks of the Nazi party after a book he wrote on euthanasia is discovered and endorsed by the Nazis.

The film is an intimate portrayal of this central reserved character and a departure from previous roles for Mortensen, with so much of what Halder is going through internalised in contrast to characters he's played such as Tom Stall in A History of Violence. For Mortensen, it's this study of an individual's actions during exceptional circumstances that makes this film so different from others depicting that era in history.

"This isn't a film about Germans or Germany," he says. "In a sense it's a film about people and what people do -- the little half-truths, the lies we tell each other and ourselves, the compromises we make which are sometimes OK and sometimes too much, that all add up and come back to haunt us.

"They can ruin a relationship, they can ruin the atmosphere of your workplace and en masse, if a lot of people are doing that, it can take a country in a direction that nobody expected." The story is more an examination of human nature than a historical one but that's not to say there weren't personal challenges for Mortensen as someone with a Danish background playing a Nazi. As a child he had heard stories through his family about German occupation, which he discovered had left him with some latent prejudices. "I've always been curious about Nazi Germany since I'd heard stories from my family about what it was like during German occupation," he says.

"Mostly out of that, and what was quite a surprise for me, I came face to face with the fact that I had some small prejudices about Germans and the German language.

"On one hand, I admired many German composers, artists, photographers but, on the other hand, I disliked the Germans and the German language.

"Once I realised I had that prejudice and started looking into it those feelings dissolved."

It's this desire to explore other points of view that drives him as an artist and sets him aside from a lot of Hollywood. In fact he describes it as his "job as an actor" to do that but he is also an accomplished composer, poet and painter.

"I certainly see it as my role to look at the world from views other than my own. My role as an actor is to understand the point of view of my character and commit to it," he says.

The exploration of the "good" of a Nazi has drawn some controversy but it is something Mortensen is quite comfortable with.

"Expressing myself in photography, in poetry, music or acting all starts with observation and trying to look at things from different sides and then interpreting those observations," he says.

Mortensen believes the reason people may be uncomfortable with the film is that the audience can relate very easily to Halder.

"It's one of those films where you can see yourself, certainly in the beginning of the story, making similar choices to the central character and it's too easy to say he's a victim, or perhaps that the Germans were just that way," he says.

"Some people feel that the film is letting Nazis off the hook or feel that here you have a nice man playing a Nazi, but the title of the movie, Good, is not to say this is a good man. It's kind of tongue-in-cheek and it leaves it to your imagination."

As he points out, the film's ending is not climactic but leaves you asking what happens next. It also leaves you wondering what Mortensen will challenge himself with next.