In his new movie, Everybody Has a Plan, Mortensen had to portray a character that carries the movie without a lot of dialogue. “When I prepare, I ask a simple question: ‘What happened between the character’s birth and page one of the script?’ And right there you can find most of the answers, even before you start shooting. I find that process really enjoyable. Just like a kid does when he pretends: It doesn’t matter how little they look like a princess or an Indian or a Viking or a sports star, whatever they’re pretending to be, they really believe it. They enjoy playing, basically. So the goal is always—in a very serious, methodical, detailed, much more layered way, I suppose, intellectually, than kids use for make-believe—to get to the same place where it’s just fun and play.”
You can read his full quote here.