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Copenhagen’ Revisited

Now that Niels Bohr’s famous unsent letter to Werner Heisenberg has finally been published—and for the most part only confirmed commentators in the differing views they already held—I have been looking back over the entire debate that my play Copenhagen seems to have provoked since it was first produced in New York in the spring of 2000, trying to work out what I still wanted to defend in my version and whether there was anything I needed to modify.

The reaction in New York, both positive and negative, took me by surprise. When I wrote the play I thought it unlikely that anyone would want to produce it. Even if I sometimes hoped I might find some small theater somewhere that would take it on, I can’t remember ever thinking that anyone would come to see it, much less have strong views about it. The successful run at the National Theatre in London, unexpected and gratifying as it was, passed peacefully. I got quite a lot of friendly suggestions and criticisms, mostly to do with my shaky science, and I made a number of modifications to accommodate them. I also came across a lot of material that was new to me—most particularly the US edition of the Farm Hall papers, with its critical commentary by Jeremy Bernstein, which made it clear to me that Heisenberg’s command of both the physics and the mathematics of fast fission was much less secure than I had supposed—and I rewrote the postscript to the published edition of the play to take account of this.

The New York production, however, opened up a much broader and more fundamental debate. A number of commentators expressed profound misgivings about the whole enterprise. Paul Lawrence Rose, the author of Heisenberg and the Nazi Atomic Bomb Project: A Study in German Culture, the most outspoken critic of both Heisenberg and my play, even managed to detect in it a “subtle revisionism… more destructive than [David] Irving’s self-evidently ridiculous assertions—more destructive of the integrity of art, of science, and of history.”

One of the most frequent complaints was that I should have laid more stress on the evils of the Nazi regime, and in particular upon the Holocaust; it was pointed out that Werner Heisenberg’s visit to Niels Bohr in Copenhagen in 1941 (the subject of the play) coincided with the Wannsee Conference. It was argued that I should have put Heisenberg’s visit to Copenhagen in the context of a number of subsequent trips he made during the course of the war to other occupied countries. It was also felt that I should have laid more stress than I did on Heisenberg’s stated view that Germany’s conquests, at any rate in Eastern Europe, were justified, and that its victory over Russia was to be welcomed.

With hindsight I think I accept some of these criticisms. I should perhaps have had Heisenberg justify Germany’s war aims on the eastern front directly, instead of having Bohr refer to his arguments in one angry but passing aside. I should perhaps have found some way to make the parallel with all the other trips that were found offensive, and about whose purpose there was none of the mystery which had seemed to attach to the one to Copenhagen.

About a greater stress on the evil of the Nazi regime I’m not so sure. I thought that this was too well understood to need pointing out. It is after all the given of the play; this was precisely why there was (or should have been) a problem facing Heisenberg, and us in understanding him. In any case the play returns to the persecution of Jews in Nazi Germany again and again, from the suppression of so-called “Jewish physics” (relativity) to the enforced flight of all the Jewish physicists, the death of Samuel Goudsmit’s parents in Auschwitz, and the attempt by the SS to deport the Jewish population of Denmark to the death camps, which Margrethe Bohr describes as “that great darkness inside the human soul…flooding out to engulf us all.”

Some of the criticisms were even more radical. The play turns on the difficulty of determining why Heisenberg made his trip. For a number of commentators there was no problem at all—they knew the correct explanation for certain; though what that explanation was varied from one to another. For some it was Heisenberg’s desire to persuade Bohr of the rightness of Germany’s war aims and of its inevitable victory; for Rose and others he was on a spying mission, to find out through Bohr if the Allies were also working on an atomic bomb.

I agree that Heisenberg may have wished to present the German case to Bohr; but he surely didn’t go all the way to Copenhagen just to do that. I also agree about the spying. But then so does the Heisenberg in my play. He tells Bohr that he wanted “some hint, some clue” about whether there was an Allied nuclear program. This seems to me to be common sense; he would have had to be insanely incurious not to seize any chance he could to find out whether the Allies might drop atomic bombs on his country. There is surely no contradiction at all with what he himself claimed his purpose was—to discuss whether the German team was justified in working on a German weapon. Any information he could get about the other side’s intentions would have been a prerequisite for deciding what to do.

Some criticisms I reject, and I should like to put the record straight. Professor Rose suggested that I had “fantasized” Heisenberg’s fear that he was in danger of his life from the Gestapo for talking to Bohr. Not so—I was simply expanding upon what the real Heisenberg said. Jonothan Logan, a physicist writing in American Scientist, dismissed as misleading the fictitious Bohr’s assertion that in June 1942 Heisenberg had been slightly ahead of Fermi in Chicago. The context makes plain that this was in terms of neutron multiplication, and the claim was based on what David Cassidy says in his biography of Heisenberg. The correctness of Cassidy’s assessment was verified for me, after much inquiry on my part, by Al Wattenberg, one of the editors of Fermi’s Collected Papers.

All these are at any rate debatable points. Other criticisms I found extremely difficult to make sense of—some even to credit. Professor Rose, who detected the subtle revisionism of the play, found a particularly sinister significance in one detail—the fictitious Heisenberg’s remarking upon the neatness of the historical irony whereby the crucial calculation (of the critical mass), which persuaded the Allies of the possibility of building a nuclear weapon, was made by a German and an Austrian, driven into exile in Britain because they were Jewish. Professor Rose saw this as an attempt to blame “the Jews” for the bomb’s invention.

A little more extraordinary still was the view of the play taken by Gerald Holton, professor of physics and professor of the history of science emeritus at Harvard. He saw it as being “structured in good part” to reflect the thesis advanced by Thomas Powers in Heisenberg’s War, that Heisenberg had correctly calculated the critical mass, but concealed it by “cooking up” a false result that killed any possibility of producing a bomb within any remotely plausible time-scale. By the time the play was produced in New York, he believed, I had been forced (by Jeremy Bernstein) to lay this idea aside, so that I now had an “unsolvable problem” with the motivation of the play.

I can only suppose that Professor Holton was misled because in my postscript I speak warmly and gratefully about Powers’s book. It has been much attacked, but I like the generosity of its tone, I like the wide sweep of its canvas and the range of Powers’s research, and I’m very grateful to him for introducing me to the story of the visit to Copenhagen. I also agree with one part of his thesis: that the German physicists exhibited a fatal lack of zeal compared to the Allies. But then so does Holton himself, and so, he says, does everyone else who has studied the matter. In the postscript to the published text of Copenhagen, however, I make abundantly clear that I don’t accept Powers’s view about the “cooking up” (though there is certainly some evidence to support it) and never did.

But you don’t even need to read the postscript to discover this, because it’s all over the play itself. The central argument turns on Heisenberg’s confession to Otto Hahn (in one of the conversations secretly recorded by British Intelligence during the internment of the German nuclear team at Farm Hall in 1945) that he had not attempted the calculation. By my count there are something like thirty-five speeches in the play devoted to establishing this, to asking why he hadn’t attempted it, and to suggesting what might have happened if he had. How anyone could give the play even the most cursory glance and fail to notice this is difficult to understand.

Even harder to credit was the reaction in some quarters to the “strange new quantum ethics” proposed by the fictitious Heisenberg. I suppose I should have erected a flashing “IRONY” sign in front of it. The allusion is to his insight, in his original introduction of quantum mechanics, that physics should be limited to the measurement of what we could actually observe—the external effects of events inside the atom. We should need a similar kind of ethics, he suggests in my play, if we judged people purely on the external effects of their actions, without regard to their intentions. According to Professor Holton, Heisenberg “exults” that under the new dispensation there would be a place in heaven even for him. Professor Holton fails to mention that Heisenberg also “exults” that, under the new quantum ethical rules, there would also be a place in heaven for the SS man who seemed ready to murder him in 1945, simply because in the end he settled for a pack of American cigarettes instead. Jonothan Logan manages to believe that I am seriously proposing even the SS man’s assumption into heaven.

Let me make it absolutely unambiguous: my Heisenberg is saying that we do have to make assessments of intention in judging people’s actions. (The epistemology of intention is what the play is about!) He is saying that Bohr will continue to inspire respect and love, in spite of his involvement in the building of the Hiroshima and Nagasaki bombs; and he himself will continue to be regarded with distrust in spite of his failure to kill anyone. The reaction of Holton, Rose, and others to the play is perhaps an oblique testimony to the truth of this judgment.

One of the most striking comments on the play was made by Jochen Heisenberg, Werner Heisenberg’s son, when I met him, to my considerable alarm, after the première of the play in New York. “Of course, your Heisenberg is nothing like my father,” he told me. “I never saw my father express emotion about anything except music. But I understand that the characters in a play have to be rather more forthcoming than that.”

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