Above is the whole interview, which is about 12 min. But because it is hard to hear at times and because it all is very subtle, I divided the tape in parts (A-P), which I transcribed below.
David Bohm: Perhaps I should go back into the history about how the ideas came about. You see when I studied quantum mechanics I was very fascinated with it, I felt that it was a very deep and important study.
But I didn’t really understand it andÂ eventually got a course on the subject and wrote a book in trying to understand it. But after finishing that book, Quantum Theory, I considered the matter again but I felt that I still didn’t understand it.
And in fact, at that time I began to think about different ideas and usually accepted ones and I sent the book to various physicists, one of them being Einstein and he expressed interest in this book so we had some discussions.
I think we both agreed that you could not really understand what quantum mechanics was about. I also sent my book to Pauli who liked it. And I sent a copy to Niels Bohr but I got no comment.
Now I’ve been thinking that any science has, theoretical science anyway, has 4 aspects. You see, our insight first of all, you see, structure, new ideas, and I said there is imagination which projects a mental image of the whole idea, notÂ only a visual image but a feeling for it.
Then there is calculation, then there is reasoning,Â rather to work out the consequencesÂ logically andÂ finallyÂ there is calculation. Get numbers, that can be, make possible precise .. experiments.
Now, I think allÂ 4Â were present evidently in physics until quantum mechanics came in.
Now in quantum mechanics, people discovered that they could find no way of imagining the meaning of the theory. And this really was brought most clearly and consistently rather by Niels Bohr. And as we were discussing before, I am not sure that any other physicist really understands exactly what Niels Bohr meant to say.
So, it is rather widely believed that nowadays, that science, at least physics does not give much weight to imagination, you see, various imaginative pictures are used like wave and particle, but they are in no sense regarded as a real description of what they are talking about. They are a sort of aids of calculation and to deploy your imaginative picture, so that you can talk more efficiently, you see that really ..
Interviewer: What do you mean by understanding?
Bohm: Well, to grasp the whole thing, to get a feeling for it, and so on. Now I don’t feel that I become proficient and calculating results that I understand what it is about. See I might make a comparison with Newtonian .. lets say that Newton developed a calculus and he would become very proficient at it, so that every time he had the .. to the .. differentiate. You could differentiate twice, you could add and subtract, you could go through all sort of operations, and you could say now finally I have become proficient, working out these operations and I could get numbers.
Some other experimental physicists .. proficient .. telescopes .. get other numbers and if .. numbers agree we feel very happy. And if we disagree we don’t, we try again. Now that would have been the way quantum mechanics .. so I don’t think Newton thought that way. He had some sort of imaginative overview of the whole meaning of the universe, he had a feeling for it of what the reality was. The body is in movement and so on under forces.
Interviewer: So you think this is why Newton is very concerned about gravitation? That he didn’t really understand?
Bohm: That’s right. He felt he didn’t, for him it was only a means of calculating, and he was not satisfied, but of course modern physicists would say, we don’t care. That is all we physicists want to do. That’s the change of attitude.
Somewhere I recall Feynman writing that imagination was the most important thing but he is an imaginative fellow, but finally it always works out that the calculation is the main thing. AndÂ I regard calculation as significant only to test the other things, the other aspects of physics. In itself I regard it as rather insignificant. I don’t think the things physicists calculate are very interesting, how many times .. going to .. how many spots will appear onÂ a photographic plate.
Interviewer: So it’s really a test of the consistency of your understanding?
Bohm: Yes, and also the factuality of it. Is it a real understanding, or is it, you know, if you haveÂ imagination you want to, an imaginative insight, you want to be sure it’s not justÂ imagination. So you have to see that it’s factual. WhenÂ Roger Bacon, I think, originalÂ suggested theÂ form of modern science, he suggests that experience should play the key part in testing.
Where as I think before that time, theÂ .. ofÂ AristotleÂ or other people had been, you see most people compare their work to Aristotle to see where that is true. But that is not so unreasonable as that may seem .. think .. you seeÂ people thought Aristotle was an authority .. disagree with Aristotle it must be wrong. And then there was a tremendously revolution .. say that experienceÂ should be the test. And this was later elaborated to saying that people should do, try to arrange special experiences which were very simple. The ordinary .. is so complicated that it’s very hardÂ to see just what it’s testing.
Now then experiments were elaborated and this is a very powerful method, but at the same time dangerous because the experiments are developed on the basis of the theory and they are set up toÂ answer the sort of questions that the theory asks, a certain theory asks.Â And then that people, theorists, once experiments were very cheap and simple, it didn’t reallyÂ matter because an other theory could be consideredÂ andÂ you could try another experiment.
But now it takes years to produce a big machine and requires the cooperative work of many people and millions of dollars. So that people feel, once you invested in this machine then youâ€™d better use it. So then theorists feel compelled to develop theories that will raise questions that can be answered by this particular equipment, which in turn will set up to answer questions .. previous theory. So the whole result now tends to .. experimental method now as developed may tend to a conservative factor into physics whereas in the beginning it was very radical and revolutionary.
Interviewer: You said this .. particle accelerator .. fragmentary view of nature.
Bohm: I think unconsciously a lot of people are questioning a particle accelerator, the very fact that they areÂ not supported .. they once were indicates that many physicists feel that they are not .. to produce the results that were expected. Now you see, if you follow these particle accelerators, they are basic, it was discovered by Rutherford that if you bombarded particles with alpha particles, you could learn quite a bit about them.
Now that depended on the idea that there was something stable about the atom which remained while you where bombarding it. Now we are using such high energies that we literally disrupt everything, create all sort of new things.
So when we compare this to try to study structured cities by bombardingÂ with higher and higher explosivesÂ and study theÂ fragments, you see. IfÂ you bombard them with light, which doesn’t destroy the city, youÂ learn something.Â If you use some kind of very fine .. you might learn something.Â ButÂ as you raise the energy, you might learn less and less rather than more and more.
Interviewer: The way .. quantum mechanics as it was and as it is today. You said there was a difficulty of understanding.
Bohm: Yes, you see I think that the difficulty is, that we have no way of understanding what is actually happening, what I call the actual fact. I think Bohr has put it that we, I paraphrase it, that we have only the phenomena, that is the observed phenomena, which .. essentially .. description.
And whereas ordinary classical phenomena like observing aÂ dot or a .. or something, were previously understood as their meaning was that they gave information about particles and so on. The particles were dependent on these phenomena, but now if you analyse the Heisenberg microscope experiment, you come to the conclusion that the experiments can not give you unambiguous information about these structures you’re supposed to be observing.
And therefore there is no clear way of considering the unknown reality which is responsible for the experimental result.
Interviewer: Now wouldn’tÂ have Bohr said thatÂ this is a fundamental property of the world. That we shouldn’t attemptÂ to ..
Bohm: Well, in effect he said that. I don’t think he ever said that directly, but it was implied in some other things he said. That is, if youÂ say that it is fundamental then I would ask how does he know that it isÂ fundamental. I mean it is only fundamental as long as the present theory works and there are a dozen ways in which it doesn’t work, as we know.
Now, we certainly can’t just accept on authority that this is fundamental. We don’t have Aristotle to tell us what’s fundamental and what’s not, you see. Now the trouble is that also our experiments can not tell us what’s fundamental and what’s not, because, as I just explained, our experiments only answer the questions that we’ve already asked.
Interviewer: What about Bohr’s views on language, on language itself?
Bohm: Well, then how does Bohr know this, you see. Does Bohr want to makeÂ .. about language and the nature. I think the nature of language is even more unknown than the nature of particles.
Bohr said that our language, put it this way, that we are suspended in language, we literally don’t know which way is up and which way is down. We’re compelled to use language and our language has certain concepts in it and he believes that our languageÂ is committed to the concepts of classical physics, at least ultimately.
You see the ordinary idea of place and time and object andÂ substance and matter, eventuallyÂ when we find, at leastÂ to theÂ concepts of particles .. position andÂ momentum.
So in Bohr’sÂ belief language, Bohr would put it that the only way of getting unambiguous communication is through the classical concept and he takes it to be the task of physics to have unambiguous communication.
Interviewer: Maybe I could ask you a question .. Heisenberg, and I asked him about the analogy .. Wittgenstein, early Wittgenstein said that the words were .. relationshipÂ to facts and the world. And then later Wittgenstein said that really it was the use of words. I took thisÂ to the analogy that maybe what BohrÂ said was too limited in a sense. That it was much,Â much more subtle in a sense than he believed.
Bohm: Yes, I should say language, first of all you can’t discuss language apart from thought. That is language is only noises unless it is expressing thought. And I don’t think anybody could presume to say that he knows the structure of thought because he would get at least, not only it is unknown but he would get into a terrible tangle if he would try to assert that he knows the structure of thought, because then we would have to say that the very thought he was thinking that structureÂ does he know that. You see, isn’t there a danger that he is projecting some idea which he has and calling it the objective structure of thought.
That is the same problem as with the machine. You see, the machines have been built up in such a way that they lead us to ask only certain questions. If you have a theory of the structure of thought, you will project it into you thought, say that’s what my thought is and than you will only ask the questionsÂ about thought that are in your theory. And your thought will only answer the questions which you ask.
AnyÂ idea which attempts to say that we know the structure of thought or the structure of language is a suspect in my idea.
For example, Chomsky has made various statements of the structure of of languagesÂ based, as I understand it, on our brain structure and he thinks we can connect it up.Â There may beÂ some insight in there, but as if he thinks that he knows the ultimate structure of language I think this is extremely dangerous. The possibility of self deception there.
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