McMurphy finds the dark truth of Nurse Ratchet and attempts to save the patients from her abuse and degradation by making them realise that they are stronger.
It's not just Nicholson's performance that makes this film a masterpiece; it's the fact that Forman was able to prevent that performance from capsizing the whole enterprise.
Nicholson explodes on the screen in a performance so flawless in timing and character perception that it should send half the stars in Hollywood back to acting school.
Watching this again, I am less inclined to regard Nurse Ratched as a simple villain, despite her vindictive humiliation of poor, shy Billy, and more like a professional who refuses to be bullied by a bunch of men.
Jack Nicholson stars in an outstanding characterization of Ken Kesey's asylum anti-hero, McMurphy, and Milos Forman's direction of a superbly-cast film is equally meritorious.
One Flew over the Cuckoo 's Nest is an earnest attempt to make a serious film. But in the end the movie backs away from both the human reality and the cloudy but potent symbolism that Ken Kesey found in the asylum.
Viewed 30 years after its release, One Flew Over the Cuckoo's Nest remains a very good motion picture, although one that perhaps just misses the pinnacle of greatness where its reputation suggests it resides.
Whatever you make of the counterculture sentimentalism in the film's story of a rebellious mental patient, [Nicholson's] performance is superb, a showcase both for his wolfish glints and for his more subtle abilities.