What is the theme in Sculpting in Time: Reflections on the Cinema by Andrey Tarkovsky?

The role of the cinema actor is a theme. As Tarkovsky explains, the cinema actor should be viewed quite distinct from the theater actor. In fact, early cinema is marred by its dependence upon theatrical styles of acting. The theater actor must fully control the journey of his or her character. The theater actor must know the full plot and their character's trajectory. Theater's essence is the actor, and so the actor must take the reins.