Who created the technique that emphasizes living truthfully under imaginary circumstances?

The technique that emphasizes living truthfully under imaginary circumstances was notably developed by Konstantin Stanislavski. His approach to acting focused on the actor's emotional authenticity and the realistic portrayal of characters in a given situation. Stanislavski's methods laid the foundation for modern acting techniques by encouraging performers to use their own experiences and emotions to create believable characters.

While Sanford Meisner, who is also mentioned, contributed significantly to acting with his own method which revolves around spontaneity and truthful reactions to fellow actors, it doesn't encapsulate the full essence of living truthfully under imaginary circumstances in the same way Stanislavski’s foundational concepts do. Meisner’s technique emphasizes the exercise of responding to other actors, which is a crucial aspect of acting, but it originated from Stanislavski's seminal ideas.

Therefore, the emphasis on truthfulness in acting, while drawing from various techniques developed over time, is ultimately grounded in the principles established by Stanislavski. This is why he is recognized as the creator of this concept.