Westerman writes that, in Kubrick’s films, the bathroom is “the room in which the human pretense of civilization falls and the only place where our animal instincts reveal themselves, for as Erving Goffman said, it is the only ‘backstage area’ where we take off our social masks and where the truth is spoken.”
This is why Jack denies seeing the woman in room 237, as she somehow represents his own hidden nature. Jack resents his wife and son for interfering with his writing, but his murderous instincts don’t fully kick in until he’s in the bathroom communing with Grady.
Likewise, other Kubrick characters reveal themselves in the bathroom. This is where Humbert Humbert (James Mason) writes his secret diary in “Lolita”. This is where Dave Bowman (Keir Dullea) finds himself after passing through the stargate in “2001: A Space Odyssey”. Looking at himself in the mirror like Narcissus, Dave experiences what we have called “the indignity of seeing himself grow old”.
This scene in particular is one that shows how Kubrick uses the bathroom to remind his characters that however lofty their self-centered human aspirations may be, they are still essentially caged animals in their bodily forms. The highfalutin “spirit life,” as Coen Brothers character Barton Fink once called it, will always be beholden to the needs of the body, which is subject to aging and the ravages of time. According to this view, it’s no coincidence when, just before the murder-suicide in “Full Metal Jacket”, R. Lee Ermey’s drill sergeant confronts Pyle (Vincent D’Onofrio) and Joker (Matthew Modine) in the bathroom with the words, “What are you animals doing inside my head in the name of Jesus H. Christ?”