“I know of no actor who is so pure onstage that he thinks only what his character thinks. If he did, he would presumably become the character: a form of madness. This may be of course what happens to Hamlet--he puts on an antic disposition, and gets stuck with it.[...]Acting is mostly a twin-track mental activity. In one track runs the role, requiring thoughts ranging from, say, gentle amusement to towering rage. Then there is the second track, which monitors the performance: executing the right moves, body language, and voice level; taking note of audience reaction and keeping an eye on fellow actors; coping with emergencies such as a missing prop or a faulty lighting cue. These two tracks run parallel, night by night. If one should go wrong, then it is likely that the other will misbehave too. [...]But there is a third and wholly subversive track that intrudes itself at intervals, full of phantom thoughts and feelings that come and go of their own volition. This ghost train of random musings is, of course, to be discouraged, but it can never be entirely denied. As Bohr and his wife, Margrethe, say in the play: "So many things we think about at the same time. Our lives and our physics...All the things that come into our heads out of nowhere.”