When film is not a document, it is a dream. That is why Tarkovsky is the greatest of them all. He moves with such naturalness in the room of dreams. He doesn’t explain. What should he explain anyhow? He is a spectator, capable of staging his visions in the most unwieldy but, in a way, the most willing of media. All my life I have hammered on the doors of the rooms in which he moves so naturally. Only a few times have I managed to creep inside.  - Ingmar Bergman