"I like to rehearse with the actors scenes that are not in the script and will not be in the film because what we're really doing is trying to establish their character, and good acting to me is about reacting"

Jim Jarmusch is emphasizing the importance of character advancement in his quote. He thinks that great acting is about responding, and that the very best method to establish a character is to rehearse scenes that are not in the script and will not be in the film. This allows the stars to explore their characters and to establish a better understanding of them. By doing this, the actors can better comprehend how their characters would respond in different situations and can bring more depth to their efficiencies. Jarmusch's quote highlights the value of character advancement in acting and emphasizes the need for actors to explore their characters in order to bring them to life.