The truth is, Nicholson doesn’t have one acting philosophy and never did. His philosophy was actually multiple different philosophies picked up over years of reading about, discussing, and practicing his craft. From Strasberg to Stanislavski, Nicholson knew his stuff but he was more than ready to adapt his approach when working with the great Kubrick.
During Vivian Kubrick’s making-of documentary (now infamous for showcasing the emotional abuse endured by Shelley Duvall at the hands of her director), Nicholson was open about his willingness to be “out of control as an actor.” More specifically, the then 41-year-old said:
“When I come up against a director who has a concept that, maybe I don’t agree with it […] I’d be more prone to go with them than my own, because I want to be out of control as an actor. I want them to have the control. Otherwise it’s going to become predictably my work. And that’s not fun.”
Demonstrating surprising wisdom, Nicholson went on to acknowledge that actors shouldn’t have “one set of theories,” adding, “You can go for years saying, ‘I’m gonna get this thing real, because they really haven’t seen it real’ […] and then you come up against someone like Stanley who says, ‘Yeah it’s real, but it’s not interesting.'”