Stanislavski's system
In his later work, Stanislavski focused more intently on the underlying patterns of dramatic conflict. He developed a rehearsal technique that he called "active analysis" in which actors would improvise these conflictual dynamics. In the American developments of Stanislavski's system—such as that found in Uta Hagen's "Respect for Acting", for example—the forces opposing a characters' pursuit of their tasks are called "obstacles".