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Physics and Beyond: David Joseph Bohm

David Bohm interviewed by F. David Peat

Most of the physicists with whom we have had conversations have tended to accept quantum mechanics as it is. They are trying to extend the formalism a little, either to unify it with relativity, or to attempt to provide an explanation for the elementary particles. I take it that you are not really satisfied with this approach.

Perhaps I should go back into the history of how my ideas came about. When I studied quantum mechanics I was fascinated with it. I felt it was a very deep, important study, but I didn’t really understand it. Eventually I taught a course on the subject, and wrote a book on it, to try to understand it. After finishing my book [Quantum Theory, Prentice-Hall, 1951], I considered the matter again, and I felt that I still did not understand it. At that time, I began to think of different ideas than the usually accepted ones. I sent copies of the book to various physicists, including Einstein, who expressed interest in it, and we had some discussions. I think we agreed that one couldn’t really understand what quantum mechanics was about. I also talked with Oppenheimer, but he was never critical enough to make possible a discussion at the level I would have liked. I sent my book to Pauli, who liked it, and also to Niels Bohr, but I received no comments from him.

Since I can’t remember exactly how I thought at that time, I’ll try to say what I now think the difficulties are. This is probably similar in essence to what I felt then. Any theoretical science has four aspects. These are: insight, to perceive the structure of new ideas; imagination, which projects a mental image of the whole idea, not only a visual image, but a feeling for it; reasoning, to work out the consequences logically; and, finally, calculation, to get numbers that make possible precise tests with experiment. Evidently all four were present in physics until quantum mechanics came in. In quantum mechanics people discovered that they could find no way of imagining the meaning of the theory. This was brought out most clearly and consistently by Niels Bohr. I’m not sure that any other physicist really understands exactly what Bohr meant to say, but I don’t think we can discuss that here.

It is rather widely believed nowadays that science, at least physics, does not give much scope to imagination. Various imaginative pictures are used, like “wave” and “particles,” but they are in no sense regarded as a real description of what we are talking about. They are merely aids to calculation; we deploy our imaginative pictures so that we can calculate more efficiently.

What do you mean by understanding?

I mean to grasp the whole thing, to get a feeling for the whole thing. If I become proficient in calculating results, I don’t feel that I necessarily understand what it’s about. By way of example, I might make a comparison with the Newtonian epoch. Let us say that Newton developed a calculus, and became very proficient at it. Every time you have the power x to the nth, you would replace it by nxn−1, and you can go through all sorts of operations until you can finally say that you are proficient at working out these operations and can get numbers. Meanwhile, some other experimental physicist is proficient at manipulating his telescope, and he gets other numbers. If the two numbers agree, then everybody’s happy. When the numbers disagree, they aren’t happy and try again. That would have been the way quantum mechanics was done. I don’t think Newton thought that way. He had some sort of imaginative overview of the whole meaning of the thing, of the universe.

Do you think this was why Newton was very concerned about gravitation, because he didn’t really understand it?

That’s right. For him it was only a means of calculating, and he was not satisfied. Modern physicists would say that they don’t care, that’s all a physicist wants to do. That is the change of attitude. I recall Feynman writing that imagination was the most important thing—and he is an imaginative fellow—but finally it always works out that the calculation is the main thing. I regard calculation as significant only to test the other aspects of physics. In itself, I regard it as rather insignificant. I don’t think that the things physicists calculate are very interesting—e.g. how many Geiger counters are going to click; how many spots will appear on a photographic plate.

So it’s really a test of the consistency of your own understanding.

Yes, and of the factuality of it also. Is it a real understanding? If you have an imaginative insight, you want to be sure it’s not just imagination, you have to see that it’s factual.

Wasn’t it Goethe who attempted to postulate a physics based upon our everyday experience, rather than on making experiments and creating artificial situations?

When Roger Bacon originally suggested the form of modern science, he suggested that experience should play the key part in testing. Before that time people thought that Aristotle was the authority for what was true and, if you disagreed with Aristotle, you must be wrong. So it was a tremendously revolutionary idea to say that experience should be the test. This was later elaborated to say that one should try to arrange special experiences which are very simple. Ordinary experience is so complicated that it’s very difficult to see just what it is testing. Then experiments were elaborated. This is a very powerful method but, at the same time, dangerous, because the experiments are developed on the basis of the theory; they are set up to answer the sort of questions that a certain theory asks. When experimental equipment was very cheap and simple, it didn’t matter if one experiment or theory did not work out, because another theory could be considered, and one could try another experiment. But now it takes years to produce a big machine; it requires the cooperative work of many people and millions of dollars. People feel that once you have invested in this machinery, you had better use it. Theorists then feel impelled to develop theories that will raise questions that can be answered by this particular equipment, which in its turn was set up to answer questions due to the previous theory. The result is that the experimental method, as it has developed, may tend to introduce a very conservative factor into physics whereas, in the beginning, it was quite radical and revolutionary.

Would you say that this is true of the particle accelerators, that they are perpetuating a fragmentary view of nature?

I think a lot of people are questioning particle accelerators. The very fact that they are not supported now to the extent that they once were indicates that many physicists feel that they are not likely to produce the results that were expected. It was discovered by E. Rutherford that if you bombard atoms with alpha-particles, you can learn quite a bit about them. But that depends upon the idea that there is something stable about the atom, which remains while you are bombarding it. Now we are using such high energies that we literally disrupt everything and create all sorts of new things.

We could compare this to trying to study the structure of cities by bombarding them with higher and higher explosives and studying the fragments. If you bombard them with light, which doesn’t destroy the cities, you learn something. If you use some sort of very fine shot, you might learn something, but as you raise the energy, you learn less and less rather than more and more.

You said that there was difficulty in understanding quantum mechanics.

Yes. I think that the difficulty is that we have no way of understanding what is actually happening, or what I call the actual fact. If I may paraphrase Bohr, we have only the phenomena, i.e. the observed phenomena, which are essentially classical in their description. Ordinary classical phenomena—the observation of a dot or a click—were previously understood to signify information about particles, and the particles were independent of these phenomena. Now, if you analyse the Heisenberg microscope experiment, you come to the conclusion that the experiment cannot give you unambiguous information about the structures you are supposed to be observing. Therefore, there is no clear way of considering the unknown reality which is responsible for the experimental result.

Wouldn’t Bohr have said that this is a fundamental property of the world?

In effect he did say that. I don’t think that he ever said it directly, but it was implied. But if he said that it is fundamental, then I ask: how does he know it’s fundamental? It’s only fundamental as long as the present theory works, and there are many ways in which it doesn’t work, as we know. We certainly just can’t accept it on authority that it is fundamental. We don’t have Aristotle to tell us what is fundamental and what is not. Neither can our experiments tell us what is fundamental and what is not, because, as I’ve said, our experiments answer only the questions that we have already asked.

What about Bohr’s view of language itself?

I would ask again: how does Bohr know that? I think the nature of language is even more unknown than the nature of particles. Bohr said that we are suspended in language and we literally don’t know which way is up and which way is down; yet we are compelled to use language.

Our language has certain concepts in it and he believed that our language is committed to the concepts of classical physics, at least ultimately. That is, the ordinary ideas of place and time, and object and substance and matter, eventually, when refined, lead to the classical concepts of particles with certain positions and momentum. Bohr believed that the only way to get unambiguous communication is through classical concepts, and he takes it to be the task of physics to have unambiguous communications. But, contrary to Bohr, I say that physics is not primarily concerned with unambiguous communications; rather that all concepts are ambiguous, and that there are certain unambiguous abstractions that can be made from our ambiguous concepts. Those are the things that we use for tests. I think people get it upside down when they say that the unambiguous is the reality and the ambiguous is merely uncertainty about what is really unambiguous. Let’s turn it around the other way: the ambiguous is the reality, and the unambiguous is merely a very special case of it, where we finally manage to pin down some very special aspect.

In his early works Wittgenstein said that words were justified by their relationship to facts in the world, but later he said that it was in their use. Perhaps what Bohr said was too limited, and language is much more subtle than he believed.

First of all, you can’t discuss language apart from thought. Language is only noises unless it is expressing thought. I don’t think anyone would presume to say that he knows the structure of thought. Not only is it unknown, but he would get into a terrible tangle, because of the very thought with which he is thinking about that structure: does he know that? Isn’t there a danger that he is projecting some idea which he has in calling it the objective structure of thought? That’s just the same problem as in machines. 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 your thought and say that’s what thought is. Then you will ask only questions about thought which are in your theory, and your thought will only answer the questions that you ask. So you are caught.

Are you saying that this is a limitation of our knowing?

I’m saying that any idea which attempts to state that we know the structure of thought, or the structure of language, is suspect in my view. For example, N. Chomsky has stated that the structure of language is based, as I understand it, on our brain structure. He thinks he can connect it up. This may be insightful, but if he thinks he knows the ultimate structure of language, I think there is an extremely dangerous possibility of self-deception.

The structure of language and the structure of thought are essentially one, inseparable. There are thoughts that go beyond language, but you cannot discuss the structure of language apart from the structure of the thought that language expresses. That is infinitely subtle, and I think Bohr might even have agreed with that. But Bohr made a still more subtle point—he was an extremely subtle person and very difficult to understand. Bohr said that he understood how subtle language is, but that physics is confined to dealing with unambiguous concepts, whose meaning cannot be doubted. Now I want to question that. Art is a field where ambiguous concepts are obviously the rule; you don’t expect an image in art to definitely mean exactly this or that. But people think that physics means exactly such and such—at least that’s the way that Bohr put it. I don’t think that physics does mean that. Physics is a form of insight and as such it’s a form of art. Every fundamental theory is an art-form in my view, and we can see how this art-form fits our general experience. No art-form fits it perfectly, so we go from one to another.

Classical physics led us to the ideal that we have a perfect correspondence between concept and fact, and thus no ambiguity. But when people study even classical physics carefully, they find contradictions. Zeno’s paradox is a case in point. The most fundamental classical concept is an object moving through space, like a particle. As Zeno analysed it, a particle is in a certain position, then it’s in another one, and another, and so on; while it’s in a certain position, it cannot be moving; when it’s moving, it cannot be in a certain position. The concept of motion involves an essential ambiguity in the position. In fact, in our mathematics, if you take a certain point, according to the theory of continuity of a line there is no next point, it is ambiguous. But it follows that the present point is also ambiguous. What do you mean by the present moment? That’s ambiguous because it’s too fast. If you try to point to what it means, you don’t get one moment, but you get some ambiguity as to exactly what it means.

You’re saying that physics has aspects of an art-form, so what criteria do you use for working in physics?

What criteria do you use in art? People have never been able to answer that question. I don’t think you can answer it in physics. People are looking for complete security by saying they know a certain criterion by which they can judge what is good physics. But any attempt to make that criterion will just kill physics, because almost any new idea is bound to disagree with that criterion. The word art in Latin is based on a word meaning “to fit, that which fits, that which is in harmony.” Ultimately, we have to see the harmony or fitting of our thoughts and our broader experience. If you have a preconceived idea of what constitutes fitting, then your mind is blocked. You may need something different.

You’re stressing the idea that science is a human activity.

It’s a creative activity.

… and a personal activity.

Well, it’s both personal and collective. But I would rather emphasize that it’s creative and not mechanical. Something new has to be created. If you have a fixed criterion of what fits, you cannot create something new, because you have to create something that fits in with your old idea. If we say “science is ‘X,’ science is something that fits a certain idea”—namely, what people have thought science is—then that limits what we can think.

If we have the concept of what fits, we’re limiting ourselves. Then how do we carry out this activity in our lives?

Is that a good question? When you ask the question “how do we do it?” you’re asking for a plan of how to go about things. This denies creativity. It is like saying “how can I become a great and creative artist?” Can there be a technique, or a plan, or a criterion?

But you wouldn’t presumably go so far as to say that a critical analysis is not involved in the way your life is carried out?

Even that has to be creative. You can’t take a fixed form of analysis. Any attempt to determine this thing beforehand is arbitrary. You are going to choose the criterion you prefer or enjoy, or the one that society enjoys or prefers.

But you must have some criterion. You’re claiming that people working with accelerators are doing things that don’t fit.

I haven’t stated a criterion. I’m just saying that if you look, you’ll see that it doesn’t fit. How do you tell that there is a contradiction? Is there a rule for recognizing contradiction? It’s the same as seeing that a picture is disharmonious or that a piece of music is not in harmony. What was once called disharmony in music later was called harmony. You can’t fix the thing.

So the notion of attempting to fit a picture onto reality is completely alien to what you’re saying—I mean the notion of a reality which exists independent of man.

There is a reality which is beyond man, and includes man, but this is unknown. A man has certain ideas which dispose him to act in a certain way. If this action is harmonious, then he regards these ideas as correct. Our thought disposes us to act in a certain way. The word dispose means “to arrange,” as a commander disposing his forces. If they are wrongly disposed, he will get into trouble, the worst trouble being the disposition of one-half of his forces against the other; that’s a contradiction. For example, you are walking down the stairs in the dark and your body is disposed to expect another stair, but it happens to be flat. The whole movement is disorganized; it is not in harmony. Then suddenly you have the thought that this is flat and the entire disposition changes. I think that’s the way all our thought works, including scientific thought. A certain way of thinking disposes us to act, in the laboratory or elsewhere, in a certain way. As long as we can find some general harmony in this action, we go on with it. When we find disharmony, we hold back and begin to look for another form of thought.

Would you say then that physics today just doesn’t fit, is not in harmony?

It’s not in harmony. Quantum mechanics has no imaginative conception. If you are satisfied to say that physics is nothing but operating a formalism to get results, and operating equipment to get results, in order to obtain results which agree, all right. But if you say that physics aims to understand what’s happening imaginatively, then I don’t think that it’s doing that. Neither relativity nor quantum theory is clear. And the relation between relativity and quantum theory is even less clear.

Was this lack of fitting, this disharmony, true even before relativity, in the last century?

There was always trouble with classical physics but it was never quite so dramatic. There have been problems such as “is there an ether?” or “is there absolute motion?” Newton had the idea of absolute space, but it wasn’t clear what he meant by it. He said the fixed stars are the frame of absolute space, but why should they be?

Have the experiments of quantum mechanics and relativity actually exposed some long-term error in our way of thinking about the world?

I don’t think it was the experiments, but the theories themselves. The insight in the theories exposed an inadequacy in our way of thinking. It implied that we should have gone further to develop new ways of thinking, but this has not been done. As Bohr said, we have only classical concepts, they are the only unambiguous concepts. I believe that we cannot understand movement if we insist on unambiguous concepts.

Did the fundamental experiments of quantum mechanics really show the error of the notion of man confronting nature as a separate object?

I think they do, but it’s a very subtle thing to analyse. Bohr has given the most consistent analysis, but it’s very hard either to understand or to express what Bohr meant. Generally the position is this. In classical physics, we say the world is made of separate objects, each a separate substance in mechanical interaction. The observing equipment is one of these objects, and therefore can be influenced by the other objects which it is observing. Evidently, you can maintain the separation of the observing equipment from the object observed and, in turn, the observing human being from the equipment, and so on. In quantum mechanics, one sees that the process by which these different things would interact cannot itself be analysed in detail. It is whole and indivisible. You cannot make a separation between the observing instrument and what is observed. For example, you are looking at this table; the form of this table has been built up by your experience which you are projecting into the table. Is the table you, or is it something separate from you? You appreciate it as a table with a certain form and a certain subsistence, but that form and that subsistence are as much you as the table. If you probed it with a very high energy machine, say with neutrinos, they would go right through, and the table would be a vaporous nebula. So the form of the table as a solid substance, or subsistence, comes from the human brain with its own particular mode of interacting. In a sense, the observer is the observed.

Something similar must occur in physics. We probe matter with certain ideas as to what to expect, and we make instruments in accordance with those ideas. In so far as the whole procedure works and fits, we say that is what it is. But later on, we will say it is something else. We once said it was a little billiard-ball atom, and now we are saying it is something very different. The difficulty is that we see a lot of new things, but then try to explain them by particles. These particles would have to behave like waves at times; they would have to pass through barriers which are unpassable; they would have to spread out like a wave and suddenly condense; they would have to jump from one orbit to another without passing in between; and so on. They would have to do all sorts of things that particles can’t do, yet we still call them particles. I think that most physicists believe that they are getting the ultimate constituent substances of the universe by discovering particles, although these particles behave in a way which would suggest that they are not that at all. By calling them particles you dispose your mind to think of them that way, in contradiction to some of the other properties that you’re ascribing to them.

So it is necessary to engage in self-examination constantly if you wish to pursue science.

You have to examine your thought, which its self-examination. People generally take their thought for granted. They pick up their way of thinking in school and from their parents. They say: “we’ll examine everything else, but we don’t have to examine thought, we’ll just think.”

By thought do you mean something different than logic?

Logic is only part of thought. Thinking is not only logical. In fact, thinking is usually not logical. People have to go to a great deal of effort to make their thought logical.

So science is not founded purely on logic.

Many would say that science is founded on logic and experiment, but I don’t think that it’s just logic and experiment.

Some feel that it’s possible to build up quantum mechanics from logic. Would you care to comment on that?

It depends on what you mean by logic. The root of the word logic is the Greek word logos, which is, according to the dictionary, the inner or essential thought of the thing. Many of our thoughts are just on the surface. It has also to do with the idea, or the word. But the question is: what is the relation between logic and reason? Reason is an activity. I call it perception through the mind. For example, when Newton saw universal gravitation as the reason for the behaviour of the planets, this was perception, it was not a deduction by logic from previous facts or ideas. Reason then is essentially perception through the mind. Logic is a way of trying to organize our thoughts so that they will be generally more harmonious. However, what we ordinarily mean by logic is a set of rules for organizing thoughts that are already in existence—arranging them, disposing them. But reason—perception through the mind—creates new orders of thought. Without this creation of new orders of thought, I think we wouldn’t get anywhere.

But it may be possible to found an existing theory on logic or on logical structures.

You can examine its logical structure if you like, but that’s not the foundation of it, you see.

Does the foundation lie in thought?

I would say that theory has no foundation. Any creative act or process has no foundation. If it has a foundation, it is not creative. If it comes from something that is already there, then it is merely the working out of what is already there, so it is not really the creation of something new.

Then what is the logical analysis of theories?

You may analyse them to see whether your ideas are clear. Very often our theoretical ideas are confused in the sense that they may point in several directions at once without our knowing it. Perhaps a logical analysis can reveal confusion; it has done so on occasion. When you see confusion, that means that you should drop the theory and try another one. If logical analysis reveals confusion then it is valuable, but I don’t think that it plays a fundamental role in the theory itself.

Would you comment on the work of David Finkelstein on logics in quantum theory?

I can’t say that I fully understand the work, so I’m reluctant to comment. The ordinary logic of common sense, which, when put in mathematical form, has been called Boolean logic, implies that a proposition is either true or false. The word proposition is interesting. It is “a proposal, something put forth.” If we took that literally, I think we could be much clearer. We could say that the function of thought is to propose, to put things forth. But there has to be an act of observation which disposes, that is, which judges between the true and the false. The judgment of a proposition should properly involve an act of observation, but in mathematics it is often an act of demonstration. This demonstration requires observation at the intellectual level, or perception. Science has generally accepted Boolean logic, but quantum mechanics has certain operators, whose value is either 0 or 1, which could be used to describe a proposition being either true or false. Quantum mechanics has sets of operators, such that you can have one set of propositions all compatible with one another, and another set of compatible propositions, but the two sets are not compatible with each other. Quantum mechanics allows us to make a model of mutually incompatible propositions in terms of sets of operators that don’t commute. You also find that when you have operators that don’t commute, something more is needed, namely a discussion of the context in which any particular operator is the relevant one.

This is true in ordinary reasoning also. For example, the statement that the electron is either green or not green. We consider the context of what we know about electrons and find that this makes no sense; it doesn’t fit the context at all; it is not a question that should be answered. Similarly, in quantum mechanics, questions could be asked about whether an electron is In a certain position or not; in another context, whether it has a certain momentum or not; but not both questions together. Consider spin for example: in one context, when our apparatus is oriented in a z-direction, we can discuss whether the spin is up or down; in another context, when our apparatus is oriented in the x-direction, we cannot discuss that, but only whether it is right or left. The two questions cannot be relevant together.

I don’t detect in Finkelstein’s work any real emphasis on this context-dependence. I think that this is a weakness. If you accept context-dependence, you can see that logic is in some sense empirical, that it is not purely a question of truth. (In fact, Finkelstein has said this himself.) Whether a certain set of propositions is relevant or not depends on the context, and that has to be seen in some broader way that goes beyond logic. One of the things that is missing is some broader imaginative concept which would show us why properties depend upon the context, or why propositions depend upon the context. I have developed an idea of this which I call the implicate, or enfolded order.

Can you give an example of what you mean by implicate and explicate order?

Take a jar of a very viscous fluid—say glycerin—and put a drop of insoluble dye into it. There is a device that turns the whole thing slowly, stirring the mixture until it becomes grey. Then you turn it around the other way, and slowly the thread of grey dye pulls together and makes the original drop again. While the fluid was grey—i.e., the dye was all spread out—the drop of dye was still there, in some form, but it was folded up into the whole liquid, or implicate. Implicate means, in Latin, “folded up” or enfolded. On the other hand, explicate order is the one that is unfolded. I can understand the quantum properties of these operators by considering that any phenomenon that is unfolded before us in a laboratory could be regarded as, generally speaking, folded up through all space.

Would this be analogous to illuminating a holographic plate and unfolding the image?

That’s right. In the holographic plate, the information about the image is present, folded up, all through the plate. Similarly, the information that determines how our apparatus is going to behave is contained, folded up, all through space. Therefore, you no longer have the model of localized objects, which are independent substances, as the explanation of everything.

In thermodynamics, people speak of entropy as being related to disorder. Disorder, to you, would be a form of implicate order?

Yes. There is no disorder in the sense of absence of order, but rather there are different kinds of order.

So is entropy a measure of implication?

I should think that you could look at it as a certain kind of measure of implication, or “enfoldment,” of the order. Since the enfolded does not appear obviously on the surface, you call it disorder because you don’t see it. But, obviously, we can’t say that anything that we don’t see doesn’t exist because we don’t see it. I think that there is an order that we ordinarily don’t see, because we are looking for something with unambiguous significance, that is, explicate. The fact that there are propositions which are not mutually compatible is a sign that the basic order is implicate. So that when one proposition is explicate, the other must be implicate, and vice versa. This would give you an imaginative understanding of why we use this logic.

Could this idea of one proposition being implicate and the other explicate be related to the uncertainty principle?

Yes. We say that all properties cannot be explicate together. But I would rather call it—as Bohr might have called it—the “ambiguity principle,” not the uncertainty principle. The word uncertain implies that it exists in a definite form and that we are just not certain of it; we don’t know of it. Rather, we should say that this property is not uncertain but ambiguous; that is, it has no clear meaning. We must give it a very complex representation in terms of many images.

Would you like to comment on the structure of mind in relation to implicate and explicate order?

It suggests a structure in which mind and matter are not very different. Anyone can see that our thought has this character, that a large part of it is implicit or folded up. When one part is explicit, a tremendous amount is implicit. As we talk, the words are explicit, but the whole meaning is implicit; we couldn’t pin it down. This implicate order is common to mind and to matter, so it means that we have much of a parallelism between the two sides. Naturally, this will require a great deal of development. The things which are well defined and explicate have to be seen as special features of the implicate order. The underlying reality is the implicate order, and the explicate order is a very special case of the implicate order.

Would you connect this with the quantum mechanical notion of wholeness and the absence of fragmentation?

This idea of implicate and explicate order obviously involves wholeness, because, in the implicate order, everything has its origin in the totality; it is folded into the totality. Moreover, the separation of the observer and the observed is no longer basic in this view. The observer is essentially an implicate order, and so is the observed. Everything that is observed is really the intersection of two streams of energy: one stream which belongs to the thing observed, the other which belongs to the observer. The “phenomena” are the result of the intersection of these two streams. Both streams come ultimately from the same total reality. There is a total reality which cannot be pinned down, it is ambiguous. It can be thought of as having many, relatively independent, streams of movement or energy. The physicist sends one stream of energy in the form of a beam of particles; the other stream is the target, which is more or less a stationary stream, moving only inwardly in the atoms; where these two intersect there arise phenomena.

The words and ideas you use have the sense of things coming into being, or time, but I think that you consider time in a very different sense?

I think that time is not the fundamental order, but a subsidiary order which man’s thought has introduced. You can see that time is full of paradoxes. If we think of the past, the past is gone. We can never get hold of the past. The future is not yet, it hasn’t come. We can never get hold of the future. The present is much too fast to get hold of; by the time you’ve said it, it’s gone. So you can’t grasp the past, the present, or the future. So what is time? Time is, at most, an abstraction introduced by thought. You cannot get any exact moment of time, except in your thought. If I describe something as happening in time, whatever I describe has already happened; it’s only present in my memory.

But the enfolding and unfolding which take place in nature surely take place in time?

We have to think that over carefully. Let’s try to see what is difficult about the concept of time. Anything that I describe is gone. Of course, it may change slowly so that it is not too different, but in fact it is gone. We may expect that it hasn’t changed very much, and in some sense that is true. But when it comes to anything which is really subtle and fast, for example elementary particles in physics, or the attempt to discuss the mind, then that short interval between the past which is gone and the present which is unknown may be all important. But all physics developed thus far depends upon the assumption that it is not important; but that’s only an assumption.

We say that the function of physics is to predict. Present knowledge is actually knowledge of the past. Also, we are not predicting the future as it is, but the future as we shall see it in the future, which makes the future into the past of the future. We never predict from “what is” to “what will be,” rather from “what has been” to “what will have been.” Then we make the assumption that what has been is very close to what is, and that what will have been is very close to what will be. What we often fail to realize is that the assumption depends not only on the slowness of movement, but also on the metaphysics which says that everything is made of things, like particles, which don’t change very much as they move, which move on a path that can be followed, and so on.

But aren’t you using “move” in two different senses, one in moving through time, and one in the movement of the implicate and explicate order?

So far I haven’t tried to define what I mean by movement. There are various ideas involved. Classical physics has the idea of the orbit as a description of movement, but the orbit is an abstraction, you never see the orbit. The past positions may be plotted on a piece of paper, but they are not seen, they are gone. They may be present in your memory, but the orbit is an abstraction which exists, as far as we know, only in somebody’s mind. Zeno’s paradox raises that point too, because it says that when the particle is here at a certain moment, the past position is gone. So how can you define movement as the relation between the present position and the past position? You would be trying to define a property that exists as the relation between what exists and what does not exist.

Some have said that time is the fundamental thing and movement is derived. Are you saying the opposite?

Movement is fundamental and time is an order which we derive. Movement is the fact with which we begin. You cannot specify movement unambiguously; movement cannot be given an unambiguous description. Look at your own experience. Do you ever actually see time? You never do. You see the position of a clock. You may remember time, but you never perceive time. The memory of time is a set of images which is present now, but ordered by thought. And that’s a clue. You do not actually experience movement by remembering a series of positions. If you are in a moving car, you feel that you are moving; you don’t say I remember that I was there, there, there. And if you project a series of positions on a screen, they are not experienced as movement until they are so close that they are no longer unambiguously separated. Then you feel movement.

Do you think there is a danger in making an analogy between movement in space and movement through time?

But I don’t know what movement through time means!

Well, people involved with relativity talk in terms of a body moving through time.

That’s what they say, but I don’t know what it means. It’s the same as for quantum mechanics, I don’t understand a great deal of what is done in relativity. If I project time t as an axis, certainly I can see the track as it’s drawn on a piece of paper, but the track drawn on the paper is not the movement.

I ask: What is movement through time? What is time? Time exists only in the mind. Does the particle move through the mind? I don’t get it! It is almost like treating time as a substance. If I say move through London, I see what that means, but move through time? First I’d have to see what time is, and then I would see a particle moving through it! But nobody sees that.

You’re saying that all these problems must be made clear before there’s any chance of making progress in physics?

Before fundamental progress is made, yes. I think that the main questions to be considered are: “what is time?” “what is movement?” and “what is thought?” I believe that time is entirely constructed by our way of thinking. You find time only by recalling images of what has been. Those images must be based on what is in the brain, but the “what is” is implicit or enfolded. Remembering the past consists of unfolding this image into a series, and we say “that’s the way it was.” The future consists of unfolding it in the way we expect it to be. But movement is not experienced as moving through these images. That is merely a way by which we know something about it; through these images we can dispose our activities toward the next step.

Actually I would like to consider the notion of flow rather than movement. There is an unknown reality which can only be described as eternal flux or flow. Out of this appear various forms which can be perceived. When these forms have a certain persistence and stability, we can recognize them and we call them objects. But we must consider our attitude to these objects. Our attitude is that all objects, such as this table or this microphone, are not only forms, they are substances, and they exist independently. Therefore, the form belongs to the substance. The other attitude is to say that they are not substance, but they are subsistence, they have a certain stability. For instance, the vortex has a certain stability in water, but it is not an independent substance. Ordinarily, we take the view that water is the substance, but if we try to analyse water into atoms we get into trouble because of their quantum properties. So I would say that the substance cannot be pinned down in any unambiguous way at all. It is unknown. But we can abstract forms in the movement of this substance. The true substance, however, is that which determines its own form.

Are things really thought to be substantial essences?

In some sense, yes. The whole atomic theory is the idea of substantial essence. It says that every atom is a substance, and that it has a form which is the form of that substance. The world is full of independent substances, one for each atom. But that doesn’t work you see. Every atom has been broken down into smaller particles and these into smaller. People call the latter particles partons. They hope that they have found the ultimate independent substance. I think we should coin a word, which I call the ultimon, the ultimate piece of independent substance, out of which everything is made. I think it’s an illusion!

But classical physics was based on that sort of illusion and it seemed to have worked quite well. People thought that they had an understanding of nature.

Obviously it works. These forms do have subsistence and stability, so a possible explanation of this is to say that they are substances.

Yes, but at that time was there a harmony or a fitting?

All theories have this character, that there is harmony and fitting up to a point. When you push them further there isn’t.

Music is an example. There was harmony and form; then it changed and we have a new harmony and a new form.

At least a search for a new harmony. Art is in much the same position; it is in almost total chaos as people search for a new form of harmony.

Would it be naive to ask whether there is a progression or just a change?

I don’t know. I think it’s primarily a change, but it’s hard to say in what sense; there’s a progress in some senses, but not in others. To define progress you must define a direction. If you choose a direction, you may discover progress, but if somebody chooses another direction, he may discover no progress.

Progress implies a target, an end-point.

Yes. I think there is no end-point and no target. The universe is an unending transformation in flux. Out of this appear these forms which have subsistence. The hardest thing of all is to see that we ourselves are only a form in this. The major reason, I think, why people find it difficult to accept this view is that it implies that we ourselves are only transient forms. The thought of the self has always been built around the idea that the self is an eternal substance, either material or spiritual, or both, and sometimes called the soul. I think that our views of matter and our views of ourselves are implicitly related. If a person is reluctant to believe that he is not a substance, he will be reluctant to believe that matter is not a substance.

This brings to mind what many mystics in the Middle Ages said about the spirit returning, rather than being permanent. Wasn’t it Meister Eckhart who believed that God was a Negative or a Nothing, and one returned to this?

Many religions have had that view, or something like it. In older times, people put their philosophical views in religious terms. The separation between art, science, and religion was a more modern development. Consider these ancient religious interests: one was the origin of things, the general structure; every religion had an explanation of this structure. First men see the world; then they see themselves as separate from nature in the world; then they somehow conceive a unity between the two in the process that created both nature and the world. This is the canonical form which people must come to. Then they invent various myths as to how this came about; they become attached to those myths; and the myths are overthrown.

Scientists have invented other, shall we say, myths as to how it came about, for example the astrophysical story. Eventually this will fade out into something unknown too. People are always trying to understand this wholeness which they seem to be separated from and trying to explain it. The way I think of it is this: suppose we take it hypothetically that when man was just coming from the animal stage, he never thought of himself as a separate being, as separated from nature in any way. At some stage man began to think “I am myself separate, I am a substance.” That may have given him some positive advantages but, at the same time, it gave him the negative feeling that he was separate from everything else, and he felt weak, lost, and alone. Therefore, man began to search to unite himself again with that from which he thought he had separated. In doing that, he invented various mythologies as to how man and the universe were created from some common source. Man is still pursuing this, but in scientific terms, rather than mythological. You notice that astrophysics gets tremendous support, not only because it’s interesting, but also because it touches on this. It means a lot to these people that they are explaining their own origin in common with the origin of the universe. That gives them a tremendous impetus to do the work.

This reminds me of the celebrations in Washington (1973) for the 500th anniversary of the birth of Copernicus [National Academy of Sciences, now published]. It was an almost mystical religious meeting in the end, the way that the scientists talked about Copernicus, as if he were a saint or a god.

One root of the word religion means “to bind up, to unite”; the other is “holy,” which has the same root as whole. Man feels separated from everything and he is always trying to bind himself back to it, to make it whole again. An ancient philosopher said that man’s activities could be divided into three basic kinds: the scientific, the artistic, and the religious; science dealing with knowledge, art dealing with harmony or fitting, and religion dealing with this search for oneness. Scientists are still searching for oneness and so are artists in some way. Religion has become highly fragmented, and people no longer believe in mythology. The fact that people with religious intentions looked into these questions in the past is not at all surprising. In fact, there is no separation. I don’t think that you will ever get rid of this search for unity, which was one side of what men meant by religion.

You mentioned the fragmentation of thought which has taken place over the last few centuries.

Thought has a tendency to fragment, to look at the world in little pieces. The situation is very extreme now, with so many different subjects of study in the universities, and none of them connected. Some people try to make interdisciplinary subjects, which in turn become more fragments. I think the general fragmentation of knowledge is producing a problem today. Once there was the idea of the whole of knowledge, but that’s obviously vanished long ago. Thought has an inherent tendency to produce fragments, to focus on one thing and then on another, then another. That is even necessary for good thought.

Could you connect this up with the idea of implicate and explicate order?

Various fragments are explicated by thought. In a hologram, you could fold up a tremendous number of pictures and any one could come out. That would be a fragment, and it would look like a whole, but it wouldn’t be.

Is it true to say that conscious thought is explicate thought?

Yes, it is fragments being made explicate. You could say the unconscious is this vast background, which is ambiguous and cannot be defined.

Does consciousness necessarily imply fragmentation?

It depends on what you mean. The content of our thoughts involves many fragments. I think that is inevitable. We have got to focus on this problem or that, and we must separate one thing from another. We cannot try to do everything ail at once. But our thought is not merely an image of things, it is also, more deeply, a disposition to act in a certain way. If we have fragments disposing us to act in different ways, that will start tearing us to pieces. We can see this happening in society, where all sorts of different views exist, and people are going in all sorts of different directions that are not compatible. Conflict arises either within one person or between people. At this point, people wish to establish wholeness, and they may try to impose it through some philosophy or some religion or some political theory as the order which will establish wholeness. It is actually only another fragment. What we want is to have wholeness in the activity of the human being, while the thought can fragment as much as it needs to, to deal with each particular aspect. At the same time, there will be all the different fragmentary views, and we must try to develop some broader views, not to impose them and say they are truth, but to see things more broadly, at the same time that we see them narrowly.

Historically we would probably say that this fragmented way of thinking was an evolutionary process, as man confronted nature and tried to survive. Do you suggest a new evolutionary step in thought?

I don’t say exactly that. Man had certain survival advantages by breaking things up, fragmenting them, treating them separately. But there are also disadvantages, as people are discovering. When you treat nature as fragmentary, dealing with one fragment after another, various problems occur, such as pollution or exhaustion of resources. It is not clear that fragmentation is an unalloyed means of survival. But this does not imply a simple return to the time before man knew his separation from nature. Once man has had the thought that he is different from nature, he can never return. There is an inherent contradiction in the assumption that man can return to nature, which makes it impossible. If he tries, he will start with his mind, which is supposed to be separate and struggling to unite. But the very struggle to unite will be an expression of the fact that he believes himself to be still separate. This is the contradiction. What man can do is to get beyond that thought. Until man had the thought that he was different from nature, there was no fundamental disharmony. But the disharmony arose when man thought that he was different, isolated in some sense, and therefore in need of reuniting. If you think it over, what he is trying to do is to reunite what has never been separated.

There has to be a very big change in our way of thinking. I believe that quantum mechanics and relativity both point, to some extent, to what step is needed. Fundamentally, the step is to be free of this division between the self and the world, the observer and the observed. I think all our thinking tends to be based on the idea that thinking is carried out by an entity, who could be called a thinker, a self, or an “I.” As Descartes said, “I think, therefore I am.” He was only expressing what people had felt for a long time. He did not invent that. One view is to say that thinking is carried out by a mental or spiritual entity somewhere inside the body—the “thinker”; that the thinker produces his thoughts, but is separate from his thoughts. Since the thinker has clear differences and properties from, say, the table, you must say that the thinker is a different kind of substance than ordinary material substance. That is what Descartes said. There are two kinds of substance: one is extended substance, ordinary matter; the other is thinking substance, which is mind. Once you have introduced this idea of separation and fragmentation, you must inevitably come to fragmenting the thinker from his thoughts, and from the world that he is thinking about.

But that separation is false and illusory, and the notion that there is a thinker inside who is producing the thought is merely imagination. What would be closer to the point would be to say that there is nothing but thought, and no “thinker” to produce it.

So this whole process of fragmentation is a process out of nature?

But is it an actual process? Is it not an illusory process?

But there is pollution, exhaustion of resources, and other problems.

Yes, but it is an illusion that there is any fragmentation in a fundamental sense. These problems are actually an expression of our oneness with nature, not of our difference. Man’s thinking tried to be different from nature and approached it in a fragmentary way, trying to treat it as pieces. But nature refuses to be treated as pieces. Man thinks these illusions, and his mind being disposed by the illusions, he creates real action which is out of harmony with reality.

So this fantasy, this illusion, is turning into a nightmare?

Yes, the fantasy produces real activities which are destructive. It is because man is one with nature that this happens.

Yes, but all these activities are part of the processes of nature.

Man’s thought is part of nature, and when man’s thought goes into fantasy and mistakes it for reality, that is also part of nature. The trouble is that man has the illusion that reality as a whole is fragmented, instead of seeing that it is his thought which is fragmented. Thought is like a bunch of maps. The maps are fragments, but you don’t imagine that the world is fragmented because the maps are. It is useful to fragment these maps because it enables you to focus on details.

If pollution and so on are part of the illusion, then what you mean by reality is very subtle.

Reality cannot be specified unambiguously. It is the flowing, an eternal transformation. Transformation cannot be pinned down unambiguously. It is movement, which means that any attempt to pin it down is an illusion. Thought makes these fragments which do appear to pin it down, and they are useful, but it is an illusion to suppose that the country doesn’t change because the map doesn’t. If you have a map published fifty years ago, and try to direct yourself through London, you will have trouble. These maps are fragmentary not only because they are broken up into pieces, but also because they are based upon the past, and the past is a fragment. The fifty-year-old map of London can give you only a fragmentary picture of the situation now. If you supposed that the situation never changed, then it would work.

Can our thoughts escape once they are tied to language?

Yes, they can, because we can look into the language. A language not only expresses our thoughts, but also helps work back on those thoughts, and gives them some fixity of shape.

But if our language is inherently fragmented, it becomes increasingly difficult to free our thoughts.

I think that our thought is in fragments in the first place, and that is why our language is fragmented. I don’t think that the trouble can be described as originating in language. It originates in the very nature of thought. Language can be considered only as a secondary process. We have developed the language which emphasizes fragmentation by having one word for an object and saying that the object acts on another one and so on.

Is it possible, then, to understand quantum mechanics or the world within the language we use at present?

I think we can, although we might also change it. Language is always used figuratively and poetically, I think; we never use it literally. The attempt to give unambiguous significance to language will never work. It is inherently ambiguous, it is flowing, the meanings are flowing. If we think differently, we will find ourselves using the words differently. Perhaps, ultimately, we will change the formal structure as well.

You have worked with language structures yourself.

I made some experiments trying to change the structure of the language, just to see what would happen. I emphasized verbs instead of nouns, to emphasize the flowing movement. I saw that you could actually do quite a bit on that line, but I finally felt that you couldn’t push it too far if you made a special language, because you would merely create another fragment. Special languages have been made and they have had a fragmentary effect.

I remember thinking that it seemed to be a language very constrained by sets of rules that you were developing.

It was more a mathematical kind of language. I was trying to “mathemate” the language so that we would not have such a sharp separation between mathematics and ordinary language.

I never quite understood what your reservations on relativity were.

They are related to what I said previously about time and movement. First of all, relativity takes the space-time continuum for granted, which implies that time is a substance, or something you move through. I don’t think that makes sense, you see. There are many ways in which relativity and quantum theory need to be changed together. There are two very elementary points which quantum theory does not deal with. One is the existence of things. Quantum theory says that nothing can be discussed except the probability of what will be observed when you have a piece of equipment. If we take the whole universe, we would have to suppose another universe of observing equipment, perhaps bigger than the first. Nevertheless, we must say that, in some sense, the universe does not require that universe of equipment; it is there without it. As Bohr said, classical mechanics did not explain that atoms are there, the most fundamental thing, the clue to something new. Quantum theory does not explain that matter is there without a tremendous amount of equipment to specify its state.

I think that every structure abstracts some things which are really folded up in the totality. They have some relative subsistence, but the attempt to say that it covers everything is going to make it impossible to be consistent.

The second thing that quantum mechanics does not discuss is the actual process. For example, if you take a single radium atom decaying into a Geiger counter, quantum mechanics proposes a wave function, half of which leaks out of the atom in two thousand years. However, in some cases something happens immediately. Let’s say that it takes ten years to decay. Since the counter doesn’t work for the first ten years, you know that nothing has happened, and that the wave function is entirely inside for the first ten or one hundred years, or whatever. And this contradicts the idea of Schrödinger’s equation, which says that it was leaking out all the time.

The theory says that Schrödinger’s equation is the most complete description possible. I say that must be wrong, and that Schrödinger’s equation is an abstraction of a fragment.

At one time you tried to look at it using the notion of hidden variables.

That is just one way of saying that there is more to it. That was perhaps too classical an approach. It was merely a way of getting insight.

Was there not some misinterpretation of what you were trying to do?

Yes. I think that some people thought that I was trying to return to classical concepts, but I was really using the hidden variables to get imaginative insight into what the theory meant. One could see that the hidden variables would have certain peculiar properties which suggested that you should look at it in another way. For example, one discovers that these hidden variables have properties which imply instantaneous connection of all parts of the universe, an extreme form of wholeness. Some people have said that it is so strange that they do not want to consider it. I don’t think that it is sensible to say that as long as we do the computation, we don’t have to imagine anything about it, so we are not disturbed by anything that happened. I don’t understand the attitude which says that hidden variables have strange properties and therefore we would rather not use them. By using hidden variables, your attention is focused on these strange properties, and by understanding quantum mechanics imaginatively, even if as not yet fundamentally, you begin to see that quantum mechanics implies something very new, which you are missing by just doing the computation.

At this point a traditional sort of physicist would ask you to produce a new prediction.

That again is a sign of a certain attitude to physics, which says that the essential point about physics is to predict something. Why do you want to predict? You would think that there is a predictive instinct which must be satisfied. But this is obviously not the case. The reason why people want to predict is just to confirm that their ideas are on the right track. I am trying to say that in some cases you cannot predict; some things are ambiguous.

Trying to see the weakness of a theory in a traditional way is inadequate. The traditional scientific method is to say: wait until your experiments clearly show that you are wrong. But if you are going along with confused methods, no experiment will clearly show that you are wrong, because you can always modify your theory. This has often been done.

We must look at it differently, realizing that there is something wrong, which the present theory does not have in it, which requires understanding, namely, there is an actual individual event—the decay of the radioactive nucleus—which is simply not accounted for in the present theory. We must put in new concepts to account for it, and see what happens, even if we can’t use them to predict anything more at the moment. I think that there is an overemphasis on prediction, on getting results, which is stifling physics. Many people don’t fully and deeply realize that there is something missing. They are so used to doing statistical calculations, and saying that only statistics matters, that they do not notice that there is an actual, individual fact which is not accounted for.

Suppose we begin by saying that stationary states just simply exist, and that the world is very nearly in a stationary state, with some transitions. Now these stationary states make jumps from one to another. We haven’t explained why that happens, we are only accounting for that fact, in which case we do not need equipment at all. We are not going to interpret quantum mechanics as what an observer would see, but as a process of jumping between quasi-stationary states. We now explain that we have what we call a material system, which is a stationary state of a large number of atoms. When you solve the many-body wave equation of quantum mechanics, you see that you cannot make this relativistic, you need to have one common time for the whole system. However, this material system is essential for relativity, because the theory presupposes some quasi-rigid material system as a frame from which to make observations. I don’t think that you could ever get any definite meaning to relativity for a single atom. You would not have a clear definition of properties such as direction in time for example.

I believe that Roger Penrose was trying to take collections of atoms, and, in that way, he thought that he could define the direction.

Penrose is working on some particular mathematical structure to try to do something which may well be worth doing. I am trying to discuss something else. I think something has to happen at a lower level as it were. Physics has given us some facts, but the actual language of discussing these facts is confused.

I am saying we must consider that this piece of apparatus, this block of matter, exists, without any help, as it were, of observers, or anything. It is in a nearly stationary state, and it determines a frame. That is missing from relativity theory; there is no clear definition of a frame. If it were not for quantum mechanics, which makes matter stable, there would be nothing in relativity that would allow for the frame that measures anything. So there seems to be a deprivation of relativity in quantum theory.

To pursue this further, you find that, if you take stationary states in one frame and then move the system and accelerate it, the stationary states of that system are not compatible with those of the first. They are non-stationary, and they correspond to operators which are not compatible. So if you have one system in a stationary state, and another system moving, the moving system is not in a stationary state relative to the first system, but it is relative to its own frame. If there were an observer inside, he would be built out of atoms in those stationary states, and he would see everything relative to those stationary states, that is, as changing. So we have an interesting conception: a relativity of stationary states. What is stationary for one block of matter is not stationary for another. That concept has been missing. In fact, we have to give the same “time” to all the atoms in one system, since we say there actually is a common time which is relevant for determining the stationary states of the first system, in technical terms, as the time-displacement operator for that system. Another system has another time-displacement operator and determines another set of states. The two systems are not stationary together.

Now, we get an extension of relativity, because we have introduced a new concept, which I call the material frame, or the natural frame for the stationary state. However, this means that Schrödinger’s equation cannot be taken as a complete account any more, because each system has its own Schrödinger’s equation, giving its own stationary states. One should not try to say that a single Schrödinger equation covers the whole universe.

We say that a particular material frame, or block of matter for example, is determined by solving Schrödinger’s equation for some atoms. This can be extended abstractly to the surrounding space, and another set of atoms which has its own frame. They may be related approximately but not exactly.

Then is space a relational notion?

Space comes out as relational space. Every particular block of matter has its space, which is extended abstractly into the surrounding region, and all these different spaces interpenetrate to form what I call a multiplex, that is, many spaces folded together. Rather than thinking of space as a single substance, we can think of it as an abstract relation of the multiplex, each element of it being a fragment that is based on one piece of matter. That is an order we are imposing on space and relating to matter.

These spaces are not all the same. We can approximately replace them by one bigger space, which some have done, and call this a real space. But I say that it is no more real than the smaller space, although it may be convenient for some purposes.

The total implications, or the metaphysics of quantum mechanics and relativity together, are utterly unclear. Every fact, you see, is presented in a framework of a set of concepts and ways of thinking. If you have a confused order of thinking, the fact will be confused. So I’m saying that the first step is to get a clear presentation of this fact. Then we can go on to develop mathematical methods of going further. When we have a set of facts, our next step is to develop a broader mathematical way of thinking, which will assimilate those facts as aspects of the mathematical concepts. I don’t think the present fact is clear enough to assimilate into any mathematical system. That is one reason why so little progress has been made over the past forty years.

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