The actor plays his most rigid character to date

Matt Damon has quietly become the most sought after leading man in Hollywood. His body of work is highly accomplished and he's easily on top of every list for choice roles. He backs it up with quality performances and is, once again, excellent as Edward Wilson in The Good Shepherd. His character is incredibly stoical, almost emotionless throughout the entire film. Any actor can overact, but playing it straight requires subtlety and control. Damon's star continues to shine with the success of The Departed and the highly anticipated The Bourne Ultimatum next summer.

This character is easily your most stoic to date. Was it difficult to play such an unemotional character?

Matt Damon: I was nervous about that. I think with another director I would have given into my fear, pushed it more and been a little more over the top. The reality was that he just insisted on absolute emotional honesty and subtlety all the time. Bob [De Niro] was just insistent on absolute naturalism and realism. He's a student of human behavior. I've never seen an actor as famous as him walk into a room and do what he does, which is he just disappears. He absolutely disappears and he sits there and he watches everything. He would just say, "You play the scene for its absolute honesty and moment to moment, don't worry about anything else."

How did you research or train for this role?

Matt Damon: The guy should be subtle. He's the head of counter-intelligence. What's he going to do, tell you how he's feeling? It makes total sense when you think about it. He should be reserved and he should be emotionally distant, because it's very dangerous for him to be any other way.

What was it like working with De Niro?

Matt Damon: He's really incredible. It's all details with Bob. Every detail was a performance. The hat, if I wore a hat, he would come and he would touch the hat. He had a very particular thing about hats and how to wear a hat. If he would see an extra, he would just go, "That's wrong." And he'd go and he'd fix their hat. It's just every little thing like that was of absolute importance to him. Nothing got spared, which was maybe to his detriment at times. Every single detail was poured over, the amount of work that went into this movie is just really incredible. This is already a legendary movie in the New York circle. The prop guys, who were the sons of the sons of the sons of people in the prop business are talking, "Oh, you were on the Shepherd." We would start at five in the morning Monday and we would finish at five in the morning Saturday. That was our five-day week. It was really gruelling, but it was all about the final movie getting done the way he wanted it to get done.

How about working with Angelina Jolie?

Matt Damon: I was just talking to somebody about this upstairs, I also experienced this working with Brad too, outside the hotel right now are 25 to 50 photographers just waiting because she's in this building. It's just this unbelievable extra thing that they bring with them, which I wouldn't wish upon anybody. And that would happen, we were shooting at the armory in Brooklyn. I'd know when she was working because I'd come to work and there would be all these people there. It would just eat away at me. But they just leave it. They just leave it behind them. She was so good in this movie, and so different from anything that she'd done. You get so caught up in all this celebrity stuff and you forget that she's an incredible actress. I don't know how she handles that stuff. I definitely couldn't do it.

A striking part of the film is its depiction of the secret Skull and Bones society. Did you come upon any crazy conspiracies?

Matt Damon: The new generation of Skull and Bones kids have gone through and have debunked everything. I mean, now there's a lot of writing about the rites of passage. Starting with around my generation, people stopped taking all that stuff quite so seriously, whereas in 1939 it was of the utmost important. But nowadays all of those secrets are kind of out in the open. Skull and Bones is co-ed now.

Getting back to your character, he ends up having a few people killed and tortured. Did you see him as ruthless?

Matt Damon: Well, nobody sees themselves as ruthless. If you look at it from his point of view, the stakes of the game he's playing, you're talking about the middle of the Cold War. In his mind he's doing things to stop huge conflagrations. It's like World War III is going to happen if I don't do what I have to do. These tough choices have to be. He's 'the good shepherd' and he's taking care of his flock. He's sacrificing, essentially, his own soul to make those decisions. That is another way to look at it.

Did playing Jason Bourne help to inform this film?

Matt Damon: It doesn't affect the way I think of the Bourne character because they're very different. In between these two Bourne movies, I did Syriana, The Departed and The Good Shepherd. Departed, at the time I signed up for it, I was thinking that it was not going to be a hit because Marty [Scorsese], classically, his movies don't make a lot of money. So I felt book-ended by the Bourne movies. I had a chance to make the movies I really wanted to make, that maybe were a little more challenging. I have a real limited chance to choose certain movies and I'm happy with the choices so far. It doesn't last forever. You guys see everybody come and go. I know the deal. I've been around. It's like you breathe this rarefied air for a real short time. There's an ebb and flow to everything.

So how's filming on The Bourne Ultimatum going? Will Jason ever get his memory back?

Matt Damon: Really well, we're almost halfway through. Paul's [Greengrass] directing it again, which is huge. That's the reason to do it because he's really just a great filmmaker. I think this should be the last one. I'm half-joking, but how long can he search for his identity.

Does he know who he is?

Matt Damon: He will by the end of this one. I don't know how long we can ride that pony. I'd like to think maybe he'll get a bump on the head at the end or something.

Who's the girl this time?

Matt Damon: Julia Stiles is in it, and Joan Allen's back also, our Bourne Girls.

Do you have any plans to write again?

Matt Damon: I don't know. The acting roles have just been so good. But Ben [Affleck] and I have been talking about it. There's one project in particular we're really interested in and maybe directing together. He just directed "Gone, Baby, Gone". I've seen pieces of it. It's just fantastic. Casey's [Affleck] really great in it and in "Jesse James" too. It's going to be a good year for Casey I think.

The Good Shepherd is in theaters December 22nd and is rated 'R' for some violence, sexuality and language.