In the film, Pitt plays Ian, a molecular biologist studying the evolution of the eye, when his life is turned upside-down by the beautiful free spirit Sofi [played by Astrid Berges-Frisbey], who leads him to question his research and beliefs.
"To be honest, I was lost every day," Pitt laughed, while talking to UPI in a recent round-table interview with reporters in New York.
Told he gave a wonderful performance in an absorbing, intelligent film, he replied, "I think that that's really a testament to Mike Cahill."
"One of the reasons I really, really wanted to work with him was ... He doesn't have a lot of films. He has one film [Another Earth], so you're still kind of guessing. He is a new filmmaker. The sci-fi genre has become about bells and whistles and how many special effects can you jam into two hours. How big is the budget? Are there spaceships? And I don't think that is what sci-fi is at its core. I think it's for the thinking men and women.
"Actually, Mike said this in another interview and I agree with it. The best sci-fi uses a metaphor to explain the human nature and that is what he did in Another Earth with a very, very small budget and what he is attempting to do with these small budgets is super-complicated. So, I think the person who was really grounding it for me was him. He is very technical. He understands the nuts and bolts of how to make a film. He knows how to run the camera. He knows how to edit, but he is interested in humanity. He is interested in love. He is a scientist who is interested in love. That's why he is a special guy."
So, did the actor think the subjects I Origins addresses were strange when he first heard about them?
"I've kind of made a whole career out of strange projects," quipped Pitt who is best known for his work on TV's Boardwalk Empire and Hannibal, as well as in the films 54, Murder By Numbers, The Village and Shutter Island.
Pitt went on to say he was immediately intrigued by the story and the questions I Origins raises about science, faith, love and destiny.
"It doesn't tell you how to think. I really love that about the film," he added.
Co-starring Steven Yeun and Brit Marling, I Origins opens in select theaters Friday.