THEME 4   Theatre...

Masks and disguise highlights the theatrical element of Kubrick's style and therefore connections well to the theme of theatre.

In 2001, theatre can be seen in the staging of scenes. Particularly when Floyd gives a speech; the tables run length ways forming two parallel lines opposite each other, and another table at the back of the room. Floyd stands at the front behind a podium when he gives his speech making him centre of the stage.
Theatre is much more obvious in A Clockwork Orange. Alex and his droogs fight a rival gang in a theatre; Alex is forced to watch footage in a typical cinema theatre; and he is tested, after the Ludovico treatment, on a stage in front of a crowd. More subliminally it is communicated that Alex craves an audience, perhaps due to the lack of attention and affection received from his parents. Alex is leader of his droogs therefore they look up to him; he forces Frank Alexander to watch him rape his wife; and at the very end of the film he dreams of making love in front of a crowd - this crowd is interesting as they are dressed in clothing from the 18th century (another theme in Kubrick's films, although less common - 18th Century is also referred to in 2001, at the very end in the suite).
The theatrical style of The Shining replaces the typical staging of a theatre; costumes of character from the party and the characters in the bedroom (bear suit and tuxedo) are examples of this theatrical style; this suggests that Jack himself (or Delbert Grady, depending on your take of the film) is overreacting and very theatrical as seen in the way he calls after Danny ("Danny boy") and his expressive gestures, and the way he announces his presence ("its Johnny").
In Full Metal Jacket, Hartman has to play a specific role in order to intimidate and train the soldiers correctly. Additionally the theatre of war; the way in which the entire film shows stages of progression towards the war ground is very theatrical.