Constantine Stanislavsky is roundly accepted as the father of modern acting theory. If you have ever studied acting, you have been exposed to at least some of Stanislavsky's ideas (whether you are aware of it or not). Stanislavsky basically created the language we use today when we talk about acting on both the stage and on camera. Terms like: objective, character motivation, actions, and through line, all are terms coined and explored by Stanislavsky.