Re-Thinking the Einstein-Bohr Debate

0:00 He was an undergraduate and graduate studies in theoretical physics in Amsterdam, and graduated with his Ph.D. in 1989. He then went to Cambridge as a post-doc in high-energy physics, and in his own words, came under the spell of Michael Atiyah and Jeremy Butterfield. So, Michael Attia took him into the area of mathematical physics, and that today is his professional bread and butter. He classes as a professor of analysis at Radboud University in Namaiken, the University of Namaiken, which is in the Netherlands. but through Jeremy's influence he got interested in history and philosophy of science he says that history and philosophy of science is a hobby most of us wouldn't agree and I think you'll see why this afternoon anyway it's a pleasure to have you here well thanks for the kindness and invitation it's a great honor for me to speak about this theme to people who probably know a great deal more about it than I do the Einstein board debate is It's a clash between intellectual giants, and as such, it's often portrayed as a high point of, say, intellectual history. On the other hand, it's surrounded by controversy. So there will be people, I'll show, who basically deny the entire significance of the debate and consider it to have been a waste of time, both the protagonists and the people who follow this. On the other hand, I belong to the camp of people who do believe it was an extremely significant event, and it was certainly a rare event that people who were so important in the history of science lived simultaneously and actually talked to each other. So the word rethinking refers to the fact that this is something like a revisionist account. So there is a party line on the Einstein board debate and its outcome, which I will review. and I was then invited to basically attack this party line as a duty that was given to me by the guest editor of the studies, Michel Janssen, who edited a volume of the Einstein Centenary, which has now appeared.

2:30 And so I just fulfilled my assignment. But the more I did that, the more I began to agree with the assignment. Now, the paper on which this talk is based, I brought a few reprints of. many from the publisher. I think only ten, for which I brought seven, all the others having gone already. So they're only meant for people who don't already subscribe to the journal or are an editor or so, since I don't have too many of them. But they're here to be taken away in any case. Also, it's very easy to find this paper on the archive or on my homepage or wherever you like. Right. Now, the question that drove me was simply the basic question in any debate, be it political or intellectual, mainly simply who won, and in the course of, well, attempting to answer this question, I began to understand what the debate had been about, but primarily I just want to ask an answer at the end of the talk, the question in this extremely primitive form, but behind the answer there is a certain amount of analysis that I hope to explain to you. Now, I'll first tell you what the party line is on who won, and I'll start with an audio-tape interview of Bohr, which was conducted the day before his death, in November 1962, which was conducted by Thomas Kuhn and other people. But the interviewer who now speaks to Bohr first is not Thomas Kuhn. In fact, I couldn't figure out who that was. But then Bohr replies, and his reply is basically the party line. But, I mean, Einstein was always a chance to be asking for precise motivation of what is, what are the principles of authoritarianism. Could you give that? You know, the prophet didn't like it. No, no. He, I know, didn't like it. But the whole thing with Einstein is so difficult to me because clearly Einstein had a lot of That he was sure that every single point, to my mind, that he was entirely wrong, and that he didn't like it. So the voices are authentic and the hands are of actors. so to expand on that you can find an almost infinite number of statements in the literature from

5:00 what's called the Bohr camp to this effect so Rosenfeld was the main assistant of Bohr during his later career and someone who even partly described as Bohr's laptop sorry, laptop, lap dog how we are corrupted by modern technology so it's not surprising that he isn't independent of Bohr And for a while his writings were fairly influential, so here's one that is typical. So the reputation of Einstein's criticism does not add any new element to the conception of complementarity, but it is of great importance in laying bare a very deep-lying opposition between Boris general philosophical attitudes and the still widespread habits of thought belonging to a glorious but very evocably bygone age in the evolution of science. So that's just one example among very many. Here's another one. In fact, in his first part of his life, that when he did his really important work, his notion of simplicity were the guide to the 20th century insofar as science is concerned. Later on, I think he was just, you know, he was completely off base. I mean, if Einstein had stopped doing physics in the year 1925 and had gone fishing, he would be just as beloved just as great and it would not have made a damn bit of difference poor guy this is the same quotation it's from a very interesting television documentary as you know Peiss is the biographer of both Bohr and Einstein except perhaps a bit more neutrality or respect but that's how it is so you could say that in the in the aftermath of the bohr-einstein debate there was a dual strategy of what i would call the bohr account consisting of two tracks one is belittling the later einstein usually combined with almost excessive tributes to the earlier einstein to just mark the contrast and the other is a deification of the later Bohr, also of the earlier Bohr, in fact, so there's no contrast in the career of Bohr, but in the career of Einstein, there's this very sharp edge, after which he got derailed, so that's the, that's what I think is the party line, and probably what most physicists would still believe and haven't read more about this, and as an example

7:30 of the second point, so this is the first point I think I have illustrated, and as I said, this is one of countless illustrations that I could have given, to the latter I'll which is just one example to make the point. That's another quotation by Peiss. And this I don't have in live appearance. But he says, I'm now ready to state why I consider Bohr to be not only a major figure in physics, but also one of the most important 20th century philosophers. As such, he must be considered a successor to Kant. And I did find a recently famous person parroting this, and this I do have. In my opinion, he is one of the really greatest philosophers of the 20th century. His penetrating analysis of what is reality, what can be said about reality, and how what can be said influences what can be real, is really a fantastic achievement. And today, it's not appreciated enough. So this is Zeidanger, who is an experimental physicist, and I believe is the most important experimental physicist relevant to the foundations of quantum mechanics. This is Vienna. It goes on with a description of an experiment related to EPR that he did underneath the Donau, or the Diamond Bay, I think you call it in English. And, well, so you see that Peiss is not alone and that the Bohr camp still survives, so to speak. Now, of course, this had to have a response. So already from the early 50s, there were various people, of which I sing a lot for here, who stood up against this. And I praise them for their courage. So they include David Bohm, John Bell, Jeffrey Boop, and Mara Beller. Now, those who know me a little bit will know that I actually tend to avoid philosophy of physics conference in order not to have to listen to talks about the Bohm interpretation or not to have to take part in the glorification of John Bell. deserve credit for his stance against the de-education of Bohr. The only person still alive in this is Jeff Boog. I'd say the first three are the physicists or philosophers of physics. Mara Beller was a historian of physics who died of cancer a couple of years ago, unfortunately. Just to illustrate the Bohr-bashing, I'll just have one quote of Jeff Boog that basically

10:00 makes the point. now one can read almost anything into these intriguing asides from Plato to Wittgenstein they reveal Bohr's philosophical hackups no more the careful phraseology of complementarity drawing on this reservoir endows an unacceptable theory of measurement with mystery and apparent profundity where clarity would reveal an unsolved problem and so you'll see that there is an extremely polarized situation where in principle the situation is difficult people on both sides. It's not that Bohr and Rosenfeld and so on don't know what they were talking about. I mean, they were half of the debate. And still, there's a certain lack of convergence that is worrying. And one of the goals, in fact, the most important goal of the debate is to, of this contribution to the analysis of the debate, is to find convergence between Bohr and Einstein. So for a while, I greatly enjoyed quotations both on the Bohr side and on the anti-Bohr side looked out for more and more and couldn't have enough but then I got completely fed up with it so the rest doesn't attempt to make peace between the camps so to speak now there are I think thousands of papers on the Einstein-Boer debate including at least a dozen of books and I'll just mention what my main sources have been I was unable to read the entire literature I doubt if anyone could even in someone being a professional in HBS as Harvey said that it is basically as a hobby but I tried to find a certain cross-section in the literature that I believe is typical now the primary literature starts and is entirely based on almost an essay by Bohr discussion with Einstein on the epistemological problems in atomic physics that as most of you will know he wrote in a festrift for Einstein that was later published as a two-volume set called Einstein, Philosopher's Science. Very nice. I hope it's still in print, since I recommend this to anyone. And that's the basic, and in a way, it's still the most complete account of the debate. But I think, as people say in English, it's written as Whiggish history. Is that right? It's history from the winner's perspective. This word, Whiggish history, by the way, was introduced by the historian Herbert Butterfield, Now, Einstein replied to this, not only to Bohr, but to all essays in this volume, and

12:30 he added all the biographical notes, and both contain some discussion of his point of view on the Einstein-Bohr debate, but not nearly as detailed as Bohr's exposition. That already weakened his case, I think, right from the beginning. Now, then other, and in fact the last primary sources, are the Einstein-Bohr and Einstein-Schrodinger Correspondences, as is dated here in the year that Einstein died. The Einstein-Borah Correspondence, you can just buy it in a bookshelf, it was published a long time ago, also in English translation, but that contains many letters that are relevant to debate. The Einstein-Schrodinger Correspondence is, I think, far more obscure, and as far as I understand, it was only discovered in the 1980s by Arthur Fein in the Princeton Archives of Einstein, and I believe it still hasn't been published. All information I'm aware of about the Einstein-Schrodinger correspondence is in two books. One is the well-known book, Shaky Game, by Fyndt himself. In another book, I'll say a bit more about a guy called Karsten Held. And this book is far more extensive than Fyndt, the Einstein-Schrodinger correspondence. And in the Einstein-Schrodinger correspondence, Einstein is far more aggressive towards Bohr than in his correspondence with Bohr, and that's natural since Bohr, in Bohr camp, where Schrodinger was his ally. You see, there's something you can certainly learn from his letters to Schrodinger, which is that it's often said that Einstein and Bohr loved each other, or even that they were in love with each other. And there's tiny evidence for this, but I think there's overwhelming evidence against it. They were polite to each other, but if you just listen to what Bohr said about Einstein, and later on I will have a second audio fragment of Bohr that doubles this. They actually thought extremely negatively about each other, I think, at least in the later phase. And this is evident from Einstein's Lettinger to Schrödinger already in the 1930s and certainly later on. Okay, so these are the primary sources. And then there are other interesting books that I enormously benefited from, that were either polarized or unpolarized, so to speak. about Bohr, it's called the Logical Analysis of Quantum Mechanics. It's not well known, although I'm sure the HPS people will have read it. It's not entirely about Bohr, but

15:00 the first chapter is an analysis of Bohr's ideas of quantum mechanics, and the reason it stands out is that he both takes Bohr seriously, and yet is extremely critical. And this combination is rare, it's not unique. Neither people fall for Bohr, or they can't take them seriously. Scheinler takes the middle ground, so it is not very much like it, so you can publish something preferable. Now, these are books that are entirely about Bohr. If you have to introduce the grey shade, the grey literature is entirely pro-Bohr, and I don't think it's very biased, and this is true for almost all books specifically about Bohr's pollen. So Peter's of Hooper, Faye, Follson, Robert Murdoch is reasonable, in fact, within this list, but still very biased, I think. Then Pikes, I think, really stands out. So the biographies of Einstein and of Bohr are very famous. I think for most people who are interested that in science, they would be the first source of both Einstein and Bohr. But the more I get to know people in the history of science, and especially in the editors of the collective papers of Albert Einstein, then the tendency is that they actually frown upon Einstein's books. And at the end of the day, I got so annoyed with both of them that I did something I'd only done with one other book before, and maybe I threw it away. and it's not politically threatened to burn books but I thought I had the right to throw books away and both of these actually threw into the dustbin and the only other book I've done it with is called The Many Worlds Interpretation of Quantum Mechanics edited by the Witt and Kray and nothing afterwards but so there is a great difference in the perception of these book-by-pice between professionals and amateurs so to speak and they're still they're still the main source on Einstein anymore go to get the right picture on the Einstein board, he made it. Well, then there's a history of quantum mechanics book. There's this multi-volume series by Meera and Reschenberg, which is not as much biased as for example, Peiss, but they were strongly influenced by Heisenberg, who was a friend of Meera and the supervisor of Reschenberg. And even the two books by Max Jammer are, let's say, Whiggish history. They're not deliberately

17:30 side, it's clear that they're not neutral either. This is not to say that these books are uninteresting, quite the contrary. All these works contain highly interesting and important information, but when you read them you have to know how biased they are. Well, then there are either pro-Einstein or neutral books. The Shaky Game is not specifically about the Einstein-Board debate, but it's certainly relevant to this. I'd call it a fairly pro-Einstein book. The best book altogether, I think, about the Einstein-Board debate, unfortunately, only exists in German. It's the PhD thesis of a guy called Karsten Held. And unfortunately, he never got it translated. He only wrote one paper in English, which is exclusively on complementarity and not so much about the Einstein-Board debate. But most of my, at least conceptual or philosophical, thinking I learned from this book, at least debate. It's still relevant and I still believe this book should be translated and what is characteristic about it that it tries to occupy the middle ground as I did but if you do this you feel naturally attracted to the Einstein side. Well then there's Bellar. So Bellar is one of these four B's I listed in the anti-Bora camp and this is the culmination of the attack. This is the quantum dialogue is extremely vicious in fact, which makes it a pleasure to read, but she went too far although like all the other books, in whatever direction it's tolerated, it's extremely informative and well researched well then, here's an interesting paper that I am sorry to put in the Boer account it's by my friend, my former friend Halverson and Clifton and they make Borg's position, and I think despite the extremely impressive mathematical argument, they still lose all reason in pursuing this goal. I think actually Hans distances himself to be from the ideology of this paper. The reason I cite it is not that I agree with it, since I profoundly disagree with the paper, but I do agree with the spirit of it, and the spirit is that they try to translate philosophical argument into mathematical theorems, and then try to decide on the basis of mathematical reasoning between philosophical sides. And this is what I'll

20:00 try to do as well later in the film. In that sense, it's a very effective example of what I would feel is the right style of philosophy and physics, of which maybe Roth was one of the factors. Well, then Howard, I think, I read a great deal by Howard, and his best not about Bohr, and certainly his paper, which is also on the web in the Cambridge compendium to Einstein, is very good. Einstein's philosophy of science has been much less described than Bohr's, as you see it is that there are lots of books specifically about Bohr's philosophy of science and physics, and there isn't any about Einstein that they're aware of, but Howard's paper certainly makes a contribution to that. And now there's a very nice paper by a guy named Whittaker, who I've never met. He also has a book on the Einstein board debate, but the paper is even better. It's partly a reply to Halverson and Clifton, but it also stands on itself, on its own, as a surveilling debate. So I learned a great deal, in fact, from Whittaker. And that's partly because, like hell, it tries to occupy the middle grounds, but then necessarily falls over. Okay, so these are the sources, and I apologize for not being familiar with literature that may actually review the point of view I'm going to defend, but the day is only 24 hours. Right, so this was the introduction, basically, and I'll try to say a little bit about what the debate was about. It's hard to analyze, because the different themes in the debate are all intertwined, so you can't really dissect it. But if you try, I would identify three points. One point is the possible completeness or incompleteness of quantum mechanics, where, as you know, Bohr defended the completeness of quantum mechanics and based his defense on ideas around this notion of complementarity. Whereas, Einstein attacked the completeness of quantum mechanics, claiming it was incomplete, on the basis of an ideology that's usually called local realism. Now another theme, though closely related, is the objectivity of physics, and specifically or technically the problem of objectification, which I'll return to in some detail, which doesn't go back to Kant, which was made famous by Kant, you could say, and which is simply the problem are when you're entitled to say that an object exists on its own, independently

22:30 of the observer watching it. So that was a central theme to the Einstein-Borre debate, and also the point of the debate where convergence will be found in their various opinions. Well, then, looming behind everything, and sometimes also confusing the debate of the earlier points, was disagreement about the purpose of physics, where Borg insisted that nature. Because Einstein existed, the physics had to be about nature. Of course this is a simplification, but it's not entirely wrong, I think, to put it in that way. So these, I would say, are the three main themes. And as I said, you can't really separate them. Every single theme sort of mixed up in their discussions with the other two, and that makes it so very hard to actually know what was going on. Now, I think it's generally acknowledged, description of Bohr, but more widely, that the debate started in the Solvay Conference in 1927, because it is the single most famous photograph in 20th century physics, or in all physics, because photography hasn't existed for such a long time. And as certainly the HBS people here know, two years ago a little film was unearthed about the Solvay Conference, and some of you will know this little film and others will not know it so I thought I should take the liberty to show it this was discovered by the great Grendelts of Mark Warren and it's only two minutes but you can actually see all these people walking around and moving so bear with me if you already know it it's very short it takes a while to come up The film opens with quick shots of Irvin Schrodinger and Niels Bohr. Auguste Pekar of the University of Brussels follows, and then the camera refocuses on Schrodinger and Bohr. Irvin Schrodinger and Niels Bohr followed by Pekar. Schrodinger, who developed wave mechanics, never agreed with Bohr in quantum mechanics, nor with Werner Heisenberg's Uncertainty Principle. Solvay gave Heisenberg an opportunity to discuss his new theory. Here's French physicist Léon Bruglain, Hendrik Kramers, Bohr's former assistant, and Paul Dirac, talking with Max Born, whose statistical interpretation of the wave function ended determinism in the atomic world.

25:00 These men, Bohr, Heisenberg, Kramers, Dirac, and Born, together with Wolfgang Pauli, represent the founding fathers of quantum mechanics. On the other hand is Louis de Broly, who wrote his dissertation on the wave nature of matter which Schrodinger used as the basis for wave mechanics. The owner of the camera, Erving Langmuir, is seen chatting briefly with Bohr. Ed Solveig-Bohr refined his thoughts on complementarity and Sparta-Weinstein over the implications. Here he's with Paul Ehrenfest. Cramer's work in Copenhagen on dispersion theory was essential to the development of quantum mechanics. Langmuir, an American chemist at the G.E. lab in Schenectady, hence the camera had recently broken his leg and appears to explain to Ehrenfest how he gets around By 1927, Dirac, in the middle, had independently developed quantum mechanics and made other significant contributions, as had Wolfgang Pauly who formulated the exclusion principle A lively Madame Curie Bourne and Pauly working out of problems Note the changed demeanor as the participants exit from the meeting except for the smiling William Lawrence Bragg and Peter Dubai Arthur Holly Compton Ellen Richardson Max Bourne Madame Curie Hendrick Cromers H.A. Lawrence Paul Langevin, Albert Einstein, whose famous response to Bourne in the statistical interpretation of the wave function was, God does not play dice. Bourne, Planck, Pauli, and Belgian soldiers, a portentous conclusion. What struck me most is that they all smoke, except Heisenberg and Iraq. And this is it. I mean, there is no more film than what I just showed. I think the same lady wrote a biography on board and published in half a year or another, you can find it back to us. Okay, so around one of the debates, roughly speaking, was about the uncertainty relations. There were other themes, and it was all mixed up with all the themes, but I think it's not a multi-grade distortion to say that it was about the uncertainty relations.

27:30 That's also the way more portrays it. And you could say that Einstein proposes experiments to refute the Heisenberg uncertainty relations. And Bohr responds by a successful move, which became fundamental in the Copenhagen implementation, which is that you have to make a change of perspective sometimes, that the measuring apparatus sometimes has to be treated as a quantum system. So the way Bohr actually refuted Einstein's arguments was that he, at a decisive point, applied to the uncertainty relations to the measurement apparatus and not only to the microsystem that's being measured upon. Now, what I would like to stress is that Einstein emphasizes the experimental context. So in 4.4 about quantum mechanics, the single most important point is that he discusses the experimental context and believes that quantum mechanics cannot be talked about without having the experimental context in the I think this point of view is actually due to Einstein. It was certainly introduced into the debate by Einstein. And I say that more generally. It was Einstein who guided Bohr towards his more mature and, I think, also correct interpretation of complementarity. So I say that initially complementarity was a complete model based on the notion of wave-partible duality that Einstein never responded to. So if you read Bohr, he desperately tries to make the issue of particle-wave duality as a central point in the foundation of quantum mechanics, and Eichsen just didn't pick up the phone. I mean, Eichsen, I think, understood these points already in the year that he introduced the photon. So Eichsen was the person who brought electromagnetism to its culmination by introducing special relativity and introduced the photon. And so I think Eichsen himself was never confused in the way that Bohr was. And as you follow the debate, this notion of wave-particle duality simply disappears from the sea. So Einstein never talked about it, and Bohr stopped insisting that this was the main point. And that led into the later version of complementarity based on the notion of a phenomenon, which I will not say much or even anything about either, because the Bohr-Einstein debate wasn't really focused on the idea of complementarity. Because again, whenever Bohr brought up even his later version of complementarity, as if we couldn't pick up the phone. But the point of view that I present here, I really learned from this book by Carsten Held, that it was Einstein who really was the driving

30:00 force and led Borg to correct his points of view basically in every round of the debate. Now, this idea of Whiggish history was certainly influenced quite heavily by Paul Ehrenfest, and Bohr, of Peis, and was more neutral than Peis, I'd say, but his writings, and especially the letters he sent, were in no uncertain terms clear about what he thought was the outcome. So they knew that Bohr won the first rounds of the debate. It is entirely backed up by this contemporary document, as far as the letter he wrote to Gudebeck and Gautschmidt, who were his collaborators at Leiden. Here's a Brussels, the originals in Germany. Brussels Boar, in the capitals, are even tests. Boar, towering completely over everybody, at first not understood at all, then step by step defeating everybody. Naturally, once again, the awful Boar incantation terminology. Impossible for anybody else to summarize. Poor Lawrence, Sir Lawrence was the chairman of the Salt Lake Meeting, of all Salt Lake Meeting, during his lifetime. Poor Lawrence, as interpreter between the British and the French, who were absolutely unable to understand each other, summarizing Boar, and Boar responding with polite despair. Every night, at 1 a.m., Bohr came into my room just to say one single word. This word was Einstein. Until 3 a.m. It was delightful to me to be present during the conversations between Bohr and Einstein. Like a game of chess, Einstein all the time with new examples. In a certain sense, a perpetual mobility of the second kind to break the uncertainty of the issue. Bohr, from out of philosophical smoke, closed, constantly searching for the tools to crush one example after the other. Einstein, like a jack-in-the-box, jumping out fresh every morning. Oh, this was priceless. But I'm almost without a preservation pro-war and contra-Einstein. His attitude to war is now exactly like the attitude of the defenders of absolute simultaneity towards him. When I counted the number of exclamation marks there, as in the original letter. Bravo, war! Although, as I said, Aaron's festival is a friend of Einstein, and they had a very warm and continual relationship. There's much more to spell in war. Okay, so then the second round is generally seen to be the EPR paper, the Einstein-Podolsky-Rosen paper in 1935, and its reply by Bohr.

32:30 And I won't go through the paper, since I think I'd say all of you will be familiar with it, or with its contents at least. But I'll just give a summary of what I see to be the main points for the outcome of the debate. So between 1927 and the EPR paper, it's felt that Einstein began to accept the uncertainty relation, but he then tries to prove the incompleteness of quantum mechanics despite the validity of the uncertainty relations, whereas initially he attacks quantum mechanics on the base of attacking the uncertainty relations. And then in this paper, the EPR correlations are described for the first time, I think it's still a matter of controversy whether she'd call them non-local. I personally believe that they're in fact not non-local, but local in a suitable sense, but this is not the subject of the talk. However, although they discovered these correlations, they did not see them as a prediction of physics, but as a reductio-ad-observative argument against the completeness of quantum mechanics, and thereby against quantum mechanics itself. So that's a discovery that was not seen as prediction by the discoverers. Now, one reason for not going into the EPR paper in any detail is that it's now, I think, widely agreed that the logical structure and also just the thrust of the paper by EPR is extremely obscure. There are various arguments for this. You can see that this is the case by the enormous amount of literature on the EPR paper. So every year there are still appear papers stating that they point out what EPR really meant. papers often contradict both each other, say if you take any pair, and contradict EPR even. So the whole literature is a mess. And there are a number of reasons for them. One is that as was discovered in the 1980s, I think, the paper was not written by Einstein but by Podolsky. And even his most famous sentence in the paper, which introduces the elements of reality, was apparently due to Podolsky and was not even endorsed by Einstein, who did not see Then they make very strange use of the projection postulate or the collapse of the wave packet in an unnecessary way. Then they have this counterfactual use of two incompatible measurements, even by this single point. There are still dozens of papers about what this could possibly mean and whether it's valid. And then they, I think, really go crazy at the end when they introduce a version of quantum mechanics with two wave functions corresponding to a single physical state.

35:00 that really doesn't mean anything. So the paper is arguably the most famous paper by Einstein, but it's very obscure. And so this is another contribution from the Bohr camp, to which I can agree in part even, although it shows breathtaking arrogance towards Einstein. Yeah, Einstein, so this is a letter of faulty to Heisenberg, immediately after the disappearance of EPR, so Einstein has once again written about quantum mechanics, together with Podolsky and Rosen. No good company, by the way. A kind of good company. As is well known, this is a disaster whenever it happens. Still, I must grant him that if a student in one of their earlier semesters had raised such objections, I would have considered a quite intelligent approach. Thus, it might anyhow be worthwhile if I waste paper and ink in order to formulate those inescapable facts of quantum mechanics that cause Einstein's special mental troubles. He has now reached the level of understanding where he realizes that two quantities corresponding to non-commuting operators cannot be measured simultaneously and cannot at the same time be described as definite numerical values. But the fact that disturbs him in this connection is the way two systems can be coupled to form one single thermal system. All in all, those elderly gentlemen like Lauwe and Einstein are halted of Inglotate. Pauli was seen as Einstein's successor for a long time, and this may be one way of breaking with his predecessor then. Pauli also had a sort of friendship towards Einstein. It's a very strange relationship that more should be written about, I think. But it's typical for the attitude in the war camp towards Einstein to write something like And in Heisenberg's reply, he does not object to the general tone of this matter, by no means. Right. Now, Bohr's reply to EPR, that again, by itself, is the subject of an enormous amount of literature with the same property that any two papers will contradict both each other and the reply. But I think you can say quite simply what the main point is. The main point in his reply is that it's nothing new, the argument of EPR. So he repeats this over and over again, not in his reply itself, but also later in his life. So he says in his reply, so the special problem treated by EPR does not actually involve any greater intricacies

37:30 than the simple examples, which is maybe the double-slits experiment and such, discussed above. And then in his survey of the debate in his Einstein test 3, Here is what we see, however, that we are dealing with problems of just the same kind as those raised by Einstein in previous discussions. Well, then he bases his reply on the notion of complementarity, which is precisely the framework that EPR attacked. So that it is as if someone advocates democracy to some dictator, and the dictator simply replies, well, in a dictatorship, it's like this. So, well, there are technical points. with EPR by single measurement, a potential disagreement is about these counterfactual double measurements, but actually Bohr agrees to most of the framework of EPR. But he then says that the EPR argument contains an essential ambiguity, and that's that they leave out the experimental context. Now, what can be said, I think, is that Bohr thoroughly overlooks the significance of the EPR correlations. And you could even say, more strongly, that he overloops the correlations themselves. And if you would say that to someone in the Bohr account, he or she would reply, yes, he doesn't discuss this, because it was so obvious to him that frontal mechanics has this property, that there was no need to say anything about it in his reply. Whether that's true, or whether he was actually aware of them at the main point of the EPR, he doesn't say anything to the effect of what we now know about their importance for the foundation of quantum. So I would say he completely overlooked the main point of the EPR paper. And he's in fact very obscure about what non-locality means in quantum mechanics, what should mean. So I think the Bohr reply to EPR is even worse than EPR itself. And to at least prove the spirit of what I say about his reply, or persuade you, I have another all-year-fragment-of-bore in which he explicitly comments on EPR. Mark says again his own voice. But don't you think that this table contributes to a great deal to purify the technology of you too? Oh, that is right. Because this compliment is absolutely a something which is no compliment whatsoever.

40:00 I mean, the whole idea is after nothing when one really gets into it. You may think, I say, too strongly, but that's really true, you see. And with the Potosolsky thing, one had to think a little. But that is something which is typical of controversial mechanics. He cannot do all the part of his business, but when they come up, what comes on? Okay, now the end of the debate, as I see it, at least the debate as it really took place, rather than later analysis of it, is Einstein's reply to Bohr in his first trip. And what he here says, I think, is generally endorsed as indeed being a fair summary. as I said, this is widely held to be obscure, I think that at this point it was made first by Arthur Fine, that this is in fact a good summary of the debate by Einstein himself as he saw it. So he writes, it becomes evident that the EPR paradox forces us to relinquish once the two, whilst following two assertions. The description by means of the wave function is complete, so that's the position of Bohr, but these are my own clarifications. Or the of spatially separated objects are independent of each other, which was his own position. And our folk wisdom has it that the first point is right, and since Einstein himself agrees that it excludes his own position, it's believed that Einstein lost the debate. But to borrow phraseology from Bohr, I say essential ambiguity remains, even in this short summary of the debate maybe this dichotomy between 1 and 2 does it apply to bare quantum mechanics as a mathematical formalism or to interpreted quantum mechanics and this became the main focus of my analysis of the problem to answer this question and having answered it to re-address the question 1 and in order to clarify this I would have to explain Einstein's and Bohr's positions overall objectification, which as I said was the problem of when you are entitled to give an object its own independent existence, independently of yourself, of yourself.

42:30 So I illustrate Einstein by a few quotations that I think make his point. First is here. The belief in an external world, independent of the perceiving subject, is the basis of all natural science. And then, one that works better in German, Das wirklich ist nicht in Gehens, sondern auch in Gehens, nach Art und Bezos. This is not the literal translation, but this is what he means, I think. Here, reality is not given to us, the problem of identifying it is posed to us, like a riddle. So what he does here, he first says, well, there is an external world, it has to be there, otherwise natural science is pointless, but it's not obvious what it is. to find it. You have to solve a riddle in order to find it. And then he presents a solution of the riddle. Maybe if one renounces the assumption that what is present in different parts of space has an independent, real existence, then I do not at all see that physics is supposed to describe. So this resonates with the first one and gives his point of view. And so in summary, his point of view is, I'd say I said realism is simply the objectivity of spatially So this is something I learned from the writings of Bob Howard, and if you look back at Einstein's own writing, it's spot on. So you could write many books about Einstein's realism, but I think this is the main part of it, the objectivity, spatially separated systems. And I do believe that HBS should be a unified field, history and philosophy of science, and that philosophy of physics should be done together with history of physics. is something about Einstein's motivation for holding these views. And I think this motivation comes from Einstein's physics, but comes from his general personality and way of looking at the world. So there's a very interesting guy called Adria Fomber, who was, as we would now call, a postdoc with Einstein in 1913 in Zunich. And he wrote a very good obituary of Einstein. It's only a few pages, but I think it makes the main points about him. And so one of the things he says about Einstein is this, here, his true passion was to penetrate the riddle of the immeasurable cosmos, which stood high above the muddle of the confusion of personal interests, feelings, and low impulses of men. Such thought comforted him, when he had seen through the hypocrisy of the common ideals of decency. The consideration of this external reality endured him as a liberation from an early

45:00 prison. So he emotionally needed this external reality. This is the equilibrous in Einstein's books that certainly make the point as well as any words, I think. And then I have Einstein making the same point himself, so he wrote a little essay of what his most fundamental beliefs were in German, and here's a translation of the main point relevant to this talk. Here, this is my own translation, which is not very good, I think, but here. I mercifully belong to those people who are grounded, as well as able, to dedicate their best efforts to the consideration and the research of objective, timely, dependent methods. How fortunate I am that this mercy, which makes one quite independent of personal faith and of the behavior of one's fellow humans, has befallen me. And he says it in German as well, so now I have a little Einstein fragment. Right, so this goes on and on. Blaubert's Buchanthus is actually on record. But this is the main point. So he had a strong emotional need for an independent world. And why he had that, we further analyze. But it's clear that I think the argument did not intrinsically come from physics for his metaphysical proficiency. Now, what about Bohr? So Bohr on objectification, as with Einstein, is entirely clear what he meant. So this would be, say, an easy part of the analysis of the debate. Because it's and there's no disagreements about what they meant by objectification. I try to summarize, as in Einstein's case, Bohr's position with a few quotations. This is a very famous one. This is from his essay dedicated to Einstein on their debate. So here, however far the phenomena transcend the scope of classical physical explanation, the account of all evidence must be expressed in classical terms. And then again, all description of experiences so far has been based on the assumption that it's possible to distinguish sharply between the behavior of objects

47:30 and the means of observation. This assumption constitutes the whole basis of classical physics. And so Bohr's realism is simply the objectivity of classical physics. So I read all these six books about Bohr's thought, and there's only one thing that I remember, and that's this. You can analyze the debate on the basis of the symbol of the future. And as a little aside, since I'm more of a fan of Heisenberg than of Bohr, it's remarkable that Heisenberg and Bohr actually agreed about the objectivity of classical physics. So I give one quotation by Heisenberg among many that makes this point here. Classical physics, science, started from the belief, or should one say from the illusion, that we could describe the world, or at least part of the world, without any reference to ourselves. That is actually possible to a large extent. We know that the city of London exists whether we see it or not. It may be said that classical physics is just that idealization in which we can speak about parts of the world without any reference to ourselves. Its success has led to the general idea of an objective description of the world." And I'd like to emphasize this agreement, because there is a whole body of literature now on what the Copenhagen Interposition of quantum mechanics is, who its founders are, and whether it's coherent. And then the point is often made that standard wisdom has it that it's a coherent body created by mainly Bohr and assisted by Heisenberg and Pauli, but that in actual fact Heisenberg and Bohr argued all the time, and there isn't such a thing as the Copenhagen interpretation. So this I also believed for a while myself, as a point made quite heavily in Myra Beller's book, for example. But I think if you look at it more deeply, that Heisenberg and Bohr did agree on the basic doctrine, which is this one, or the two quotations. What they disagreed about was complementarity. But this is the core, I think, of Bohr's approach-responsive mechanics, and so it's chaired by Heisenberg. And I'll also actually say more about that later on. Okay, so as I said, based on the example of Halverson and Clifton, the general strategy that I follow is to try to translate philosophical positions into mathematics and then decide by means of a theorem who is right philosophically. And so I hope you can bear with me a brief mathematical interlude which either uses operator algebras. Some people expect me to use the word C star algebra in

50:00 But the conclusion of this, to those who are not familiar with the language, is easy to state without any mathematics, but I still would like to give the main mathematical point that backs up my conclusion about the debate, and it's this. If you have two physical systems, they will be described in quantum theory by what they call C star algebras. It's not totally you won't just think about Hilbert spaces or states or so on or apparatus. But abstractly, you use a certain algebra that describes, mathematically describes the observables of the system, A and B. And you can think that this is more general, what I say here. But you can think of A as being the observables of an apparatus, and B as the observables of a quantum object. Well, then you can take the tensor product, and that describes the total system of apparatus and measured object. Then there is an option of separability, and I mean you say that a state, a state is here meant in the sense of a positive linear functional, so it's not a wave function, but a wave function is a specific example of a state in this sense, so the wave function divides a state in this sense by taking the expectation value of an observable solution, now you say that a state is separable when it's a mixture, or in fact some, technically, of product states, so a states are those that factor. So if you have A as an operator on the apparatus, and B is one pertinent to the quantum object, and some states have this property and others don't. So some states factor over the tensor product and others don't. In fact, the overwhelming majority of states do not have this property, but some do. And if you have a separable pure state, then that has the property that it is determined by its restrictions to A and to B, which are pure as well. Another is an interesting way of looking at developing qualities, which is that if omega is pure, then omega is separable in this sense, if and only if it satisfies the developing quality in a certain phrasing relevant to this type of language, and you can call this browser originally Holt. Alright, and then the main claim to the theorem that will decide between Einstein and Bohr

52:30 will be something that's usually called Roger's theorem, although I learned recently that it's due to an earlier author called Bitschock, namely that all pure states on the tensor product are separable if and only if at least one of A or B is commutative. Not necessarily only both, but at least one of them. That's a very nice expository paper by Guido, about this theory around. And I also explain it in the paper that was distributed. So that's the mathematical interlude, and it's not the deep result effects. And if you use this mathematical result, then you will see how Einstein meets four. So I repeat the main points of their approach to physics. I mean, as Einstein's realism is the objectivity of spatially separated systems, as Borat realism is the objectivity of classical physics. Now, if in the previous discussion you take, as I said, A to be the apparatus and B to be the quantum object on the study, then objectification of B, according to Einstein, or according to his notion of local realism, means that all pure states on this tensor product must be separable. That's backed up by involving Bell's theorem, but even without Bell's analysis this follows, sort of confirmed by the Bell inequalities I gave them. Then he had objectification of B according to Bohr, which is that A must be commutative. That's what's often called his doctrine of classical concepts, which I summarized in words in the quotations that I gave. And then by this rego or Wittstock theorem, actually the criteria of Einstein and Bohr coincide. So their philosophies of objectification in physics look different when written down in words, but if you translate them into the relevant mathematics pertinent to quantum mechanics, they're actually the same. And this leads me to a reassessment of the question, who won the debate? Nightly, I repeat the quotation of Einstein's reply to Bohr, so Einstein gave us a choice between, one, the description by means of the wave function is complete, which is Bohr's position, and two, his own position, the real states of spatially separated objects are independent of each other. And I ask, well, the essential ambiguity in this way of putting it is, does this dichotomy applied to bare quantum mechanics as mathematical formalism, or to interpret as quantum mechanics. And then everyone will have to acknowledge, I think,

55:00 that Bohr was never interested in the bare or any formalism of quantum mechanics. In fact, people like Mara Beller claimed that he was not even familiar with the formalism of quantum mechanics, not even at the level of a first-year course. So he was exclusively interested in its physical predictions. And therefore, the dichotomy must be about the interpreted theory. But about the interpretive theory, Bohr and Einstein basically agreed that you have to describe the measuring apparatus classically, that their positions match. Now, it's clear that the theory interpreted in the sense of Bohr is manifestly incomplete, because you reduce a non-commutative algebra to a commutative sub-algebra, so you lose a great deal, at least, let's say, half of the description. and therefore by my previous analysis the interpretive theory according to Bohr satisfies the position of Einstein so my conclusion it was Einstein who won the debate this is the statue of Washington it's opposite the National Archives and so this turns the tables around However, he won the debate on the term of the debate, as I see it, but you could still ask whether he was right or not, because they spoke about quantum mechanics to each other in certain terms, but we have a better understanding of quantum theory now. Well, I believe that both Einstein and Bohr were wrong about the objectivity of the classical world, and the fact that there are a few things that I strongly believe, and that I think many people now believe, which is firstly that the quantum world is objective but inaccessible, and that the classical world is accessible, but after a long struggle I find the word perspectival, I think suggested by Jeremy at the end of the day, you could say a relative, and there are many other things you could say here, but it's not independently existing and the classical world does not stand on its own as an objective reality. I mean, if And I tried to do this in a very lengthy paper in the Handbook on Philosophy of Science, or Philosophy of Physics, edited by John Urban and Jeremy Butterfield. So I defend this point of view in this paper. The conclusion, I think, of modern understandings of quantum mechanics is that the classical world is as much observer-dependent as anything would possibly be in physics.

57:30 where Bohr and Einstein and Heisenberg would agree that it's observer independent, and I think also Bell had that point of view. Now, this is basically based on mathematical analysis, but I believe that both many world theorists and modal interpreters will agree with this. And you can even look at a certain version of the Copenhagen interpretation that supports this point of view. So my conclusion is that although Einstein won the debate, He wanted, heads down, the work of Michel Janssen as he summarized my paper in the introduction to this issue, Studies. But this is not the subject of this talk. This is just a post-scriptum, so to speak, that we need all the talk about a whole lecture series to be backed up. But I'd like to end with a bit of fun that summarizes the whole course of the debates. I'm almost at the end now. I think what this is a total of is the fall and rise of the later Einstein. So as I tried to illustrate repeatedly, I think the Bohr camp suggested that Einstein got derailed after 25. So 25 is the year used by Peis in this TV fragment. And so one reason was his allegedly irrational criticism of quantum mechanics. Another that I didn't mention, but that was certainly used as well in Peis' biography, field view which is hopelessly misguided and wrong. Whereas I think the right point of view is that Einstein was well on track after him in 1925, maybe he was even greater than before. So what I think most people would agree now is that EPR was a tremendous inspiration for quantum physics. It led to developing qualities, it led to entanglement, it led to quantum information, or at least heavily inspired these fields. There's evidence that Einstein In fact, behind many of Schrödinger's ideas, particularly the Schrödinger-Cat idea, arose from the correspondence between Einstein and Schrödinger. Einstein solved the measurement problem from the beginning. And some people would say that unified field theory is a step towards string theory or other notions of unification that are in fact now very popular in physics. So I think the tables on action have been entirely turned over the last decade or so, or maybe you did before. And I had one quotation by whom I already identified as my favorite author in this whole

1:00:00 area, Carson Held, which I think would be the moment view on Einstein, certainly a view that I support, which is that during this clarification process, the name of quantum mechanics, Einstein was the first to raise certain issues that still occupy physicists and philosophers, such as the separability of spatial distance systems, or even more importantly, the measurement problem. however, were merely stepping stones towards a more fundamental critique. Einstein eventually unearthed the conflict between quantum mechanics and seemingly unavoidable common sense opinions of physical reality. So I'd say that he made an altogether positive contribution to debate them. I'm glad that he did not go fishing in 1925. Now what about Bohr? So this was the fall and rise of the later Einstein, and with Bohr I think it's the opposite. It's the rise and fall of the later Bohr. So, the literature on Bohr, until recently almost, portrayed him as someone like the Gandhi of 20th century physics. So, he defeated Einstein, the most brilliant thinker of the century. John Wheeler compared him with Buddha, Peiss compared him with Kant, and you could go on and on. In fact, I think Bohr was So he was a philosophical and a mathematical bilatant. Complementarity. This week we'll discuss these points. I think he's an obscurantist in more sense. He hardly followed the physics of the day, but he stifled opposition by a spellbinding friend and foe. Thank you. On this one. Right. We have plenty of time for discussion. I'm sure that many of you will want to speak. Simon? Well, what can I say? In philosophy, we've got a principle which is that if you have an interpretation, which ends up concluding that completely mistaken, then that's a fact go bad interpretation. I think that's roughly what's going on in this talk. I put an alternative view of Bohr, and I'm not supportive of Bohr, but it's this, that when you conclude that for Bohr, one of the mechanics was interpretive, one of the mechanics

1:02:30 is manifest and complete, that really is not even to get beyond 101, because Bohr, he of view, and this is what complementarity is about, that you only have a fragment of classical concepts of view, and that this, moreover, is a consequence of the quantum action, the existence of quantum action, which is an argument I think he never managed to make out, it was what he repeatedly tried to make out. So, you know, the view that quantum mechanics is incomplete will amount to the view that would reject this great lesson that was supposed to be in the quantum mechanics, namely that A, quantum mechanics, classical concepts are irreplaceable. He's a dominantist about that. But B, the way to get novelty and to do new physics is to use only fragments of those concepts. And someone who still holds the quantum mechanics as incomplete, would be somebody who just denies that we can only use a fragment of classical consciousness. And that would then be somebody who denies the existence of a form of actual forces to only use a fragment of classical consciousness. Yeah, but this analysis is completely wrong. I agree that this was his analysis. No, no, I agree. I agree too. I think after that we were on the same side, but before he did a very bad job in this case, and he was obscurity, and he was obscurity, so without that keen link, does it or does it not follow him in the way, but we can only use a frankly practical concept. But that's what his claim was, so suppose that he's committed to the new incompleteness in Turkey. Well, it has to be clear that that was not his own view. I just say that he was, that he would be, there's terminology used by you guys, that you would be coherently forced to take that stance, I think. You see, the main point about these fragmented classical descriptions is that I believe, with Ferguson Health, that the idea that they are mutually contradictory, but still supplementary classical descriptions is a contradiction. It's absolutely nonsense. That you can have two classical descriptions that are both incompatible and yet jointly provide a complete description But he never says that. The idea is that the best description you can give, given the experimental context, is some subset of classical concepts. That's the best description.

1:05:00 And then, if that's the best description, I say it's incomplete. So he's forced into admitting that. which, in his language, is to insist on the classical written scripture, which combines both space-time qualitization and causal reason. Yeah, but he was the first to make the correct point that you've only got one of them. So he has to choose, and by choosing you satisfy Einstein, incidentally. And that is an incomplete description. Now, I don't see how we can be saved there. I should actually clarify that I support the doctrine of classical concepts. So the idea that you have to understand quantum through classical is, I think, spot on and maybe enough to make him a genius. And that's because that explains the notion of probability in quantum mechanics. But all the rest, I mean, that's an insight, and then he should have backed down. But after this insight, he would have had to agree that that leads to an incomplete and nearly probabilistic description. But the point of view that you have a probabilistic description that comes from this doctrine of classical concepts, which yet is complete, is incoherent, and also unnecessary, I think. Jeremy, do you want to add? Well, I wanted to make a short supplementary question, but I think in asking it, it will have prompted the class to say a bit more about this final remarks just now. Because when you were first discussing it, it seemed that part of what was going on was state versus observable. Because in your Einstein 1, because one has to regard the quantum mechanics interpreted as incomplete, that meant algebra B is commutative, and it's therefore less than the full algebra of the object system. And, but of course in most discussion we often gloss complete versus incomplete as about the state of their variable, you know, if there's some concept of state which is an extension of the given concept, which, so the theory is partial or incomplete. so but yeah these things are sort of two sides of the same kind but perhaps you should say more about can you say more about your probable idea that the classical restriction is spot on because

1:07:30 of its forcing a probabilistic concept in connection with my trying to to defend suppose I was kind of Simon Prime, a sidekick of Simon at the CIM, and I say, well look, he believes that the quantum state can't be supplemented, and the commutativity of B is the incompleteness of quantum mechanics, because heck, incompleteness quantum mechanics means required to supplement the state, and he certainly would resist that. Yeah, so that's not, yeah, okay, so maybe this indeed clarifies the debate. There are two different, or many, but at least two different notions of incompleteness, of which I discuss perhaps an unusual one. So the usual notion of incompleteness or complete applies to the wave function or state. And all debate about hidden variables and so on is about that notion of incompleteness or completeness. Whereas I would say, once you truncate a certain algebra observables, or let's say a description of a physical system, in such a way that the truncated description is classical, then there can be no discussion that you have arrived at an incomplete description. Yet that's what you must do, according to Moore and according to myself. This, I think, is the only way to understand quantum mechanics. And if you do that, you will see that the state that was initially pure on the whole system, and therefore complete, according to orthodoxy, becomes mixed. It becomes probability distribution on classical measure space, so to speak. So it all matches and is a good description, unless it's combined with the completeness claim, because you have explicitly given up completeness in the desired sense, namely that you give a complete description of the measurable documents. So although I should have separated these two notions of completeness, the one I use I think is coherent and relevant to the debate. I think where I could further agree with you, what you said, is that Paul didn't understand mathematics with quantum mechanics. I don't think he did. He certainly never looked to quantum mechanics to get clear about interpretation. What he did is he looked at experiments. So I think when you frame it in terms of what he's doing with the left of the theory, indeed

1:10:00 He says that they're truncating the theory in a certain sense, no question that what's left is a fragment of what we had before. But his entire message, it really was an entire message of incomplementarities. Classical concepts are, you have to use them, and because the problem of action, you must use only a subset, and this is how we get novelty. Now, if that's his position, to accuse him of incompleteness would be difficult. He would, I think, rightly say, oh, okay, sure, if you mean that it's incomplete, because, you know, by definition, complementarity means you've only got a fragment of the classical description. No, but he messed this up by claiming that you had another classical description that together with the other one forms a complementary view of reality. I think that we differ in our understanding of complementarity. Yeah, let's discuss this now over here. But now the further point is that, so one would say, sure, it's incomplete in that sense, but now if you're telling me there's some further description possible of the phenomenon which uses the full set of classical concepts, then I all will deny that such a thing is possible because of the existence of quantum action. So that would be Paul's comeback to the accusation of incomplete as meaning, there's some further description possible from the classical concepts. And the big problem, actually, is one of those is the pilot-based theory, which really does seem to be a complete description of the classical concept. So I think that's just such a shame that we've never addressed that question. No, but his allies did, and there's correspondence, I think, with either Pauli or Heisenberg at Bonn, in which they defend from the poorest point of view. I usually go to philosophy and physics meetings because I don't want to discuss the pilot. So I think it was in this paper, on the archive, you offered a more optimistic scenario where Warren Einstein rather than the adversaries actually collaborated with some sort of cooperators. Can you say a bit more about that? What do you think might have happened? That's based on this, the very slide I had, I mean, well, so the outline of the thought was that although they disagreed about many things perhaps, the central point of the debate is or could have been the problem of objectification, physics, then they had different looking criteria which in fact mathematically coincide, and that's where they could have become friends.

1:12:30 So that's the optimistic part of this. I think they both give a seemingly different criteria, which I support, and that they're valid. But I support it from the side of the core, so to speak, and then reach Einstein's because it's equivalent, and other people might do the opposite. And so, in addressing what is objective in physics, they simply agree, and specifically in quantum physics. And so that's the peaceful message, so to speak. And also, this I agree with both Einstein and Heisenberg, so I will put it back to you. Throwing in complementarity just means confusion. I mean, the analysis is clear until people start using this word. And that's, I think, Bohr's negative contribution to the foundation of quantum mechanics. this doctrine of classical concepts is brilliant, absolutely profound insight, but he made a model of it by combining it almost seamlessly with a different doctrine called complementarity, which then went through various different phases as well. And that's my position. As long as you don't mention complementarity, you have Einstein and Heisenberg on your side, and you have a coherent picture of the debate where Warren and Einstein agree. But you're welcome to have a... See there. A few copies... I have a few copies left. Maybe I could... With permission, I could put myself in a queue. I myself wrote a review or analysis of the Einstein-Bor debate many, many moons ago. I think that I would disagree with you about many things I agree with you about. But I think one of the things I would disagree with you about is perhaps going back to what you call the first phase of debate. I don't think the first phase of debate was about the uncertainty of relations. And let me say why. The first phase of debate involved a number of thought experiments. One of them involving a single slip of the hemispherical detector. And that really is a rerun. I mean, it's a predecessor to the EPR argument, just with a different mechanism. But it's all about, it's really about locality.

1:15:00 In a sense, that 1927 theme is just reproduced in a different context in 1935. Another thought experiment involved the famous diaphragm hanging on a spring. Now, that didn't involve the uncertainty relations in Einstein's mind. That involved, indeed, complementarity, because Einstein was claiming it is just not true in general, or he was attempting to argue, it is not true in general that it's impossible to have a single experimental context that picks up both the wave, namely interference, and the particle context. Interestingly, Bohr's reply, which is famously, as you mentioned, he applies the uncertainty relations to the diaphragm. In this particular instance, he's using the uncertainty relations to justify his take on wave particle dualism. But in his early debate with Heisenberg, several years earlier, not several years earlier, but shortly beforehand, where he's discussing how Heisenberg is supposed to present the gamma ray microscope experiment, he insists that wave particle dualism, as applied to the photon, is what accounts for the uncertainty relations holding to the electron. So in other words, it's precisely the opposite logic. Be that he changed his mind, or this is a very good indication of Bohr's opportunism. But just coming back to the question of what Einstein was doing, of course in 1930, Einstein came up with a photon on the boxes. Now that does represent a deviation from everything else. That's the one point where Einstein does seem to be questioning the correctness of one prediction. Yeah, although... But I think it is an exception. I think otherwise the main arguments in 1927 are really precursors to the arguments in 1935, except now in 1935 he can hit Bohr because what Bohr is constantly talking about, the unpredictable, irreducible effect of the process of measurement on the system, but now because of the EPR system he can use locality to prevent that kind of language. So that was really the important insight in 1935. I entirely agree with the points you make. I tried to give a rather coarse-grained description of the various rounds of the debate, and once you add detail, this happens to any coarse-grained description, I think. The description is undermined. It's more subtle than a rough description. On the other hand, if you add all the details, you can't give an outline. So it's true. I agree with all your points.

1:17:30 I just want to come back a little bit. I don't agree with that much. Look, here's my basis. Look at Heisenberg's seven paper and seven two editions, and look at the final paragraph there. Look at the Comer lecture, and what Paul says, and the speech into Heisenberg, and this is the claim. What is an issue is not the interaction of the system by the measurement process, this is disturbing the system that we're supposed to waste this is the definition. The possibilities of definition is very clear on that in 27. And that's exactly what he comes back to with that fact. There were one or two occasions in the Koerner lecture when, I would say contradicted it, but he did, he talked about, and this is part of the issue of his missing argument, of the resistance of one of the action to why is it an effect on one of the other concepts available, where he talks about an interaction as an irrational element, and there the language seems to indicate a disturbance in general. But it's contradicted by various explicit studies in Camelot as well, which are repeated later on. So I don't think the textual evidence is there that Paul propels to disturb the spectrum. It's Heisenberg who did so, Well, there is contradictory literature about this. Yes, I mean, in the 1935 we were replying to Eisenhower's course, it is the most peculiar concatenation of different points of views because there's no doubt that there's a very strong operationalist disturbance type discussion at the beginning of that paper. I do take your point because, I mean, there are passages where Bohr is definitely talking I think there is a rationale that makes sense to him, it's this, he does use the disturbance picture in accounting for why do you sort of work in the subject towards another. So why can't you make, why can't you make, why can't the man reach a tune in the platform and they're able to talk about what you can predict on the one towards the other, why that the issue about what does that imply for what comes definable, that's a separate issue, and that can be at a distance.

1:20:00 Well, there's a lot there. Okay. It seems to be in the 1927, at least as reported by Bohr in the Schultz report, Bohr had sort of two events. One was a disturbance idea and reckons. And the other idea he had always was the complementarity philosophy. And all of the examples in the 1927, in Gore's report, the 1927 debates, he's always able to comply with history. Mechanism and disturbance always come in just at the moment that the very last one would save the day. And complementarity is vindicated. What's interesting about the 1935 paper of Gore's reply about three-quarters of the way through the paper, they've got courage. He tries to make a disturbance explanation of Einstein's example, and he can't. It's plain. You can just claw a line, not in the paper. I tell you, look at the tape. Let's do it. And then there's a deep breath, and then he chooses his horse. Yeah, that's what I thought as well. This is the point of view of Beller and Fein, which I endorse, but I'd be happy to be correct about it. So I would agree, but I would acknowledge the possibility that this is wrong. So I read it in that way too. I just have a question in order to clarify for myself your main point about the mathematical reconstruction. Put on the slide again where you have the old mechanics. Old mechanics? Yeah. Well, they... Where you construct it first, like 4 and 5. Yeah, a little bit. Oh, you're running on... Is the, uh... Is the front not connected, or... It's on. The red light's on. Red light's on. Right. Well, maybe the problem was here. It's not connected to your little cube, that is. Sorry. Okay, so now I'm glad we survived the talk on a few instances. Where is the mathematics?

1:22:30 Yeah, I was just wondering, so the way in which they go inside is saying that Well, EPR for the United States exists if and only if A and B are both non-commutative. And both of them would deny that because B, according to his philosophy, must be commutative. And Einstein would deny it because if he would, then he would have a non-commutative. So they denied for different reasons. at the point, and that's because their criteria for objectivity are different on this phrase, and these criteria are their reasons for the denial, but what they deny is the same at this point. So, what they deny is the same, but the reasons are not the same, so they coincide on their result, but not on their actual position. Yeah, I was criticized for that. so this point is shared by others and the conclusion has to be probably that if you translate philosophical argument into mathematical argument you lose something and the question is how important it is what you lose and I'd say just lose some luggage but you don't lose the focal point you don't lose your life but it's true that this mathematical translation may not do justice to their actual positions And it's hard to reply to this because some people give philosophy privacy over mathematics or I would do the opposite. I wouldn't want to do that if I wanted to tell you. No, the point is absolutely valid and unanswerable in a way. I was fortunate because I wanted to make a comment that looks supplementary to Genesis in two ways. wonder specifically about what you just said. I mean, it seems to me when you go from informal to formal, you can always worry that you've lost something. But even when you haven't lost something, it's true that we're not, none of us logically omniscient, not even, you know, these figures. And so they could have a reason for believing something, dip out, and yet what they believe is the same, and they're not aware that they both believe the same, because they can't

1:25:00 see the inference because they haven't got the language and so in a sense this comes up often in philosophy debate that the geezers committed to something that they deny and you can prove it to them and they might give in so yeah that you know even without a loss from going from informal to formal it can just be not seeing an inference and it's a biographical fact but yeah I think the logic is clear that their reasons come to the same, because, I mean, their reasons aren't, so to speak, once formalized logically far from the very content on which they agree. Yeah, an interesting example is Lenin and Trotsky. Trotsky moved to the Menshevik party, whereas Lenin was the Bolshevik party. And so between 1905 and 1917, they thought they had completely different ideas about what the Russian Revolution should be. But when and saw what the actual circumstances are, they acknowledged that they actually had precisely the same goal, joint forces and the rest of his history, as they say. And that this might be similar. And they were able, unlike Bohr and Einstein, I think, to control their egos, gigantic as they were in Trotsky and Lenin's case, but nonetheless in the interest of their cause. And that spirit is totally absent from the Einstein-Bohr debate. I think there was no, I think, more on the side of Bohr than the search for reconciliation or agreement or common ground. It was very defensive, I think, for both sides, especially for Boers, although they could have meant it, as I tried to share. I've got a related second part to my comment, and that is just that it's very interesting in your construction on this, which we see vividly on this slide, that your capital A Whereas when I first read a draft, I was thinking Rauch's theorem would be applied to the two components of an EPR. No, you don't get the conclusion. Yeah, that's right. I mean, you've entirely endorsed this part of your story, but it is necessary then to regard this as the climax of the story, which isn't really a story about EPR 1935, it's about the debate as a whole. And I also think of slightly racism in a sense. I endorse your remarks by the irony that what Einstein denied and Bohr ignored is actually the most positive part of EPR's story.

1:27:30 But there's no exact... There's a slight disjunction between this irony and this centerpiece of today's story. That's right. This confirms the layout of the talk, I think, since what Einstein denies and what Bohr ignores... It's not part of what I see as the main problem, the problem of objectification. So in a way, quite rightly they ignore it. So what I try to see is what I see as the main point, and I think they saw it as the main point as well, but didn't see their convergence. So EPR they would still disagree about, but it's not the main point of 30 pages, I believe. I agree. Yeah, and another aspect of all this worries me greatly, I mean, it's something else that was written about, which is a knock-on effect. And what I find is very worrying about the story, if you were right, and I hear you're agreeing with James Cushing and you're agreeing with Maribel. So it sounded to me that you can hear great irrationalism in the late 20s and 20s. No, I don't say that. I read your paper about this, which I agree with. What is irrational? I mean there were clear arguments why there It would have been rational for supporters of quantum mechanics to follow the leader. Oh, this is completely rational. I don't agree with Cushing at the moment. I didn't list Cushing because his name doesn't start with B. If it had, I wouldn't have listed him either in the main opposition against Bohr. But if it's so muddled, I mean, if it's the desperately unintelligible complementarity, if Bohr basically won the day through God knows what, obscuration and so forth. Well, I think he won the day because he proposed a solution to an obscure and enigmatic situation. And I think for many people it was enough to know that he, the Great Boar, had proposed a solution, rather than knowing what the solution actually consisted of. That seems to me an awful betrayal of integrity that we have, I can see. That's not a betrayal of integrity. It's utterly rational, I think. Well, he had done great work in the past.

1:30:00 This becomes almost a psychological analysis now, rather than the mathematical one I intend to discuss here, although what you think. I was going to say, while I was speaking very badly about philosophy and philosophies, this is the smallest specter of the philosopher of the age. Indeed. And that's what happened. It was their philosophy. That's right, that's what happened. because he got he took care of all that philosophy yeah that's what they thought I think that's yeah that's another quotation that I omitted by Murray Gell-Mann who wrote also I think in the 70s that Bohr managed to brainwash a whole generation of physicists that the problem was solved by him 50 years ago but it was an effective it was necessary in order to do all these computations in quantum mechanics that led to solid-state physics and high-energy physics without having to bother about the interpretation. And this Bohr achieved that they didn't have to bother, because he allegedly solved the problem. I'd like to maybe step in again. I'd like to make an endorsement and then raise a query. The endorsement has to do with Scheiby's study. And I very much agree with you. This is a really, a very, very good study of Bohr's in the game. And a couple of points that I got from Scheiby, not just the importance of understanding Bohr's principle, the totality of the quantum phenomenon, particularly after 1935, and how that was clarified by the EPR debate, but also Bohr's own recognition, and this is frequently forgotten, Boer's own recognition that complementarity and the uncertainty relations were pushing opposite directions. In other words, Boer himself was aware that you could, that complementarity didn't have, as it were, its formal characterization of uncertainty. That was the historical reason, you know, I invented something to back up or explain. No, I agree, it was a huge shift. Yes. But now I'd like to come back to this other aspect of Bohr thinking that you, I think you basically agree with and extoll, which is this sort of semi-transcendental argument that runs all the way through Bohr's writings, to the effect that you couldn't do science, that you couldn't communicate objective states of affairs. Yeah.

1:32:30 Something that's, in other words, the outcomes of experiments have to be described objectively. It's so much the definition of science, yes. But, I don't really understand why this is any different from something like a version of scientific realism or, you know, I mean, what is so profound about this? Unfortunately, this attack is sometimes used as a way of getting around the measurement problem. Oh, that inside...