Scientific theories, at least in physics, are mathematical. It is a dangerous thing to try to say what the math really "means." And when we think we know what it "means," it is more dangerous still to extrapolate that "meaning" into other areas of life. But we do it all the time. This play extrapolates concepts from quantum mechanics onto the relationship between Bohr and Heisenberg. And it does so in a thought-provoking way.
If the uncertainty principle says that position and momentum are uncertain, what about history? Is it possible to know for certain what happened at that meeting in Copenhagen in September 1941?
What about uncertainty in our thoughts? "There is not one single thought or intention of any sort that can ever be precisely established...[T]his uncertainty in our thinking is also fundamental to the nature of the world." (postscript, p. 99)
If the complementarity principle says that an observation is required for something to be made "real," does that also apply to our thoughts?
Bohr [as Heisenberg is standing on the doorstep about to enter Bohr's house for the fateful dinner and conversation]: Until this instant his [Heisenberg's] thoughts have been everywhere and nowhere, like unobserved particles, through all the slits in the diffraction grating simultaneously. Now they have to be observed and specified. (p. 86)
I know that my own thoughts don't seem to coalesce until I either speak them or write them down. (It is one reason that I blog.) I have heard others say the same about their thoughts. In some sense our thoughts are not "real" until either spoken or written down, i.e. observed and specified.
A major theme of the play is what quantum mechanics says about humans. It may surprise you:
Bohr: We put man back at the centre of the universe. (p. 71)
Over the centuries, science has put humans farther and farther from the center of the universe. Science has made humans less and less special, as compared to the rest of nature. Bohr's point, at least in the playwright's words, is that since quantum mechanics (at least in the Copenhagen Interpretation) requires an observer to create reality, humans are pretty darn special.
Two pages after the above quote, we have this humorous exchange:
Bohr: Not to criticize, Margrethe, but you have a tendency to make everything personal.
Margrethe: Because everything is personal! You've just read us all a lecture about it!
As usual, I think it best to let the woman have the last word.