Miscast: The Body on Stage

When an actor walks onto a stage and says the words a playwright has written, whose body is it?

Not legally. Legally the question is settled. The actor owns the body, the playwright owns the words, and an intricate web of union contracts and intellectual property law keeps the two from colliding in ways that require attorneys. The legal answer is clean. I am asking a different question. I am asking what happens, at the level of consciousness, when a human being stands in a defined space and pretends to be someone else. Whose experience is the audience receiving? The character's? The actor's? The playwright's? Some fourth thing that does not exist until all three converge in a room where strangers have agreed to sit in the dark and watch?

I have spent more than forty years in the theatre, and I do not have a settled answer. What I have instead is a book.