Even when you expose something, when you have a true believer, that person rejects that proof; he thinks it's just a set-up. We believe what's more convenient for us to believe. We always behave this way. We start with the conclusion, and then we create a body of theories around it. We choose what allows us not to change.

Something that I wanted to do through the film is try to explore the roots of belief, because everything has to do with beliefs. When I studied the side of the rationalists and the skeptics, and the side of the believers and so-called psychics, I found out that both of them, no matter what they claim to do, behave in a very similar way. They only accepted what confirmed their previous positions, and tended to reject everything that put them at risk.

Debunking certain things is important, first because you question things, which is always healthy, and second because there's a part that has to do with show biz, which is pretty harmless, but there's another part that has to do with people's vulnerability. That needs to be exposed.

And as a director, you constantly try to solve problems, so you have to focus on that. You take away all the other parts. Of course, when the shot finishes, you remember that you have Robert De Niro in front of you. But when you're shooting, you just see a character in front of you, and an actor, and you try to search for very truthful moments. That's what obsesses you.

If you believe in God, that's a belief. If you are an atheist, it's a belief too, because you cannot prove that God does not exist.

Once I do something, I need to be obsessed - or maybe I don't need to be obsessed, but I get obsessed because that's just the way my brain works - but I need to pay a lot of attention to detail. Because everything counts to me once I do something, even if it's a movie that nobody cares about. That's why I need to choose very well what I want to do. But in real life, when I watch TV or whatever, I guess I'm not that obsessive guy, and I'm pretty boring.

There are a couple of things that are, in the present, floating in front of my face, and once one of them gets enough energy to become a voice that I cannot not hear, then I will become a steamroller. When you've made your film, you stop hearing the voice.