Lee Smolin's realism

Lee Smolin is a respected physicist who has always had strong philosophical interests and convictions. He recently articulated his realist views in a public lecture. What follows are my notes on his lecture mixed in with a few comments and observations.

Smolin is strongly opposed to postmodernists who reject the notion of objective truth and who see reality as a social or historical construct. He draws parallels between the anti-realism of postmodernists and the anti-realism of certain physicists associated with the development of quantum mechanics (QM) and the so-called Copenhagen interpretation.

Smolin claims (as Einstein did) that QM is an incomplete theory and so, in a real sense, wrong. The key problem with QM as Smolin sees it is the so-called “measurement problem”. It relates to the notion of wave–particle duality and the two laws or rules that QM provides to describe how things change over time. Rule 1 or law 1 says, in effect, that (except during a measurement) the wave evolves smoothly and deterministically (somewhat like a wave on water). This allows the system to simultaneously explore alternative histories which lead to different outcomes all of which are represented by the smooth flow of the wave. Rule 1 applies when you are not making a measurement. Rule 2 applies only when you make a measurement.

Smolin argues that the 2nd rule means that QM is not a realist theory. If we (or other observers) were not around, only rule 1 would apply.

One of the main developers of the theory, Erwin Schrödinger, was uncomfortable with the theory and its implications. He crystallized his doubts in the form of the famous live/dead cat-in-the-box thought experiment (which is explained by Smolin in his talk (starting at 39.54)).

Niels Bohr, in contrast to Schrödinger, embraced the paradoxical nature of QM, partly because it fitted in with ideas which he had developed previously. Bohr’s notion (or philosophy) of complementarity was shaped by these ideas and by the observed behavior of elementary particles. Sometimes such particles seem to behave as if they are waves, sometimes as if they are particles and, crucially, how they are observed to behave depends on the details of how we go about observing them.

Smolin takes an unequivocally negative view of Bohr’s metaphysical views as well as of the views of Bohr’s protégé, Werner Heisenberg. Here he is on the former:

“Now, of course, Bohr had a lot to say about things being complementary and in tension all the time and you always have to have two or more incompatible viewpoints at the same time to understand anything, and that especially goes […] for knowledge and truth and beauty. And he got off on the Kabbalah, of course. Anyway [long pause] … it doesn’t cut it with me.”

For Smolin, QM's incompleteness is intimately bound up with its incompatibility with realism.* QM is not consistent with realism because the properties it uses to describe atoms depend on us to prepare and measure them.

“A complete theory,” insists Smolin, “should describe what is happening in each individual process, independent of our knowledge or beliefs or interventions or interactions with the system.” He is interested in understanding “how nature is in our absence.” After all, we were not around for most of the history of the universe.

Smolin defines realism as the view that nature exists independently of our knowledge and beliefs about it; and that the properties of systems in nature can be characterized and understood independently of our existence and manipulation. Our measuring etc. “should not play a role in what the atoms and elementary particles are doing.” What he means, I think, is that our interventions should not play an essential or crucial role in the descriptions and explanations which our theories provide.

“A theory can be called realist,” Smolin explains, “if it speaks in terms of properties whose values do not require us to interact with the system. We call such properties “beables”.”

By contrast, a theory whose properties depend on us interacting with a system is called operational. Such properties are called “observables”.

Observables are defined as a response to our intervention. Beables, by contrast, are not defined as a response to our intervention. They are just there, it seems.

But how do we get to know the values of these properties unless we interact with the system? Also, there is the framework question. Properties and values arguably only exist within the context of a particular perspective or theory. In order for properties and values to be properties and values, we need to conceptualize them as such. I will ignore this broader question, however, and focus on what Smolin means by interaction.

Even ordinary observations (like seeing or hearing or recording something electronically) involve us or our measuring devices interacting in some way with the system we/they are observing/recording. Smolin appears not to be concerned with such interactions here because, although the nature of the observer’s perceptual apparatus and/or the nature and settings of the equipment being employed determine or pick out what is and what is not being observed or recorded, the results are otherwise quite independent. The type of datum is determined by the nature of the observer or the observing or recording process, but not the data themselves.

In the case of experiments with elementary particles, however, the situation is subtly – and sometimes dramatically – different. Interactions are such that they determine, or play an active role in determining, the values in question.

Arguably, ordinary cases of measurement and observation do not pose problems for the commonsense realist. But if our observations alter in a material way whatever it is which is being observed – as appears to be the case in respect of the quantum realm – problems arise.

Operationalism was first defined by the physicist Percy Bridgman (1882–1961). The book in which he elaborated his views, The Logic of Modern Physics, was published in 1927, the same year QM was put into definitive form. Bridgman’s philosophical approach has much in common with the instrumentalism which characterized the views of the majority of thinkers (physicists, logicians, philosophers) associated with logical positivism. Bridgman was in fact personally involved in the activities of the Vienna Circle.

It was the physicist John Bell who introduced the concept of beables. According to Bell – and according to Smolin – it should be possible to say what is rather than merely what is observed. This is all very well but – quite apart from philosophical arguments questioning the notion of a noumenal world – experimental results continue to come out against the realists. Experiments with entangled particles, for example, seem to exclude the possibility of any form of local realism. Some form of nonlocal realism is still very possible however.

Smolin is at his weakest when he talks history. The story he tells about the generation of physicists who grew up during the Great War is hard to swallow. It seems that they were predisposed to anti-realism by virtue of the unusual circumstances of their early lives. They had witnessed at an impressionable age the destruction of the social optimism of the 19th century, and so were skeptical of rationality and optimism and progress. They had lost older brothers and cousins and fathers and uncles and had “nobody above them ...” No wonder they didn’t believe that elementary particles etc. have properties which are independent of our interactions with them!

You would think that the fact that Niels Bohr, the father of the Copenhagen interpretation, was not a part of this generation would sink Smolin’s generational explanation from the outset. As would even a cursory knowledge of the history of 19th century thought which is shot through with various forms of idealism, anti-realism and radical empiricism. The phenomenalist philosophy of science of Ernst Mach (1838–1916) is a case in point. At the end of the 19th century, Mach articulated ideas which were later picked up by the thinkers Smolin is criticizing.

Smolin explicitly recognizes that Bohr’s main ideas were formed well before the development of quantum mechanics and that he was influenced by 19th century thinkers – including by Kierkegaard (whom Smolin clearly does not hold in high esteem).

Smolin quotes some of Bohr’s claims:

“Nothing exists until it is measured.”

“When we measure something we are forcing an undetermined, undefined world to assume an experimental value. We are not measuring the world, we are creating it.”

“Everything we call real is made of things that cannot be regarded as real.”

Heisenberg followed the same general approach:

“The atoms or elementary particles themselves are not real: they form a world of potentialities or possibilities rather than one of things or facts.”

“What we observe is not nature itself but nature exposed to our method of questioning.”

Bohr said: “We must be clear that when it comes to atoms, language can be used only as in poetry. The poet […] is not nearly so concerned [with] describing facts as [with] creating images and establishing mental connections.” What he meant, presumably, is that the normal referential function of natural language cannot be used in relation to the quantum world, and anything we say about that world (using natural language) will necessarily be a creative construct shot through with metaphor and paradox.

Maybe so. Or maybe not. It is not something we can know a priori. It all depends on how our models develop and on the results of experiments. But, until QM is subsumed into some (hypothetical) broader theory which allows us to envisage quantum processes in more intuitive or realism-friendly ways, Bohr's general views regarding the radical inapplicability of natural language and ordinary logic to quantum events or processes will remain plausible.



* There is also the question of gravity. Quantum field theory brings together QM and special relativity. QM and general relativity have yet to be satisfactorily reconciled, though a line of research associated with the so-called AdS/CFT correspondence – a string theory-based approach – has made considerable progress towards this goal.



This is a revised version of an essay published at The Electric Agora on June 4.

Knowledge of the past, knowledge of the world

Is it acceptable to distinguish between, on the one hand, an account of the past (whatever kind of account it may be) and whatever it is which such an account is, or purports to be, about? I ask this question because I was challenged for using this form of words in a recent discussion with Daniel Kaufman. Not only would I argue that it is acceptable, I would say that such a distinction (or something very like it) is necessary to make sense of the very concept of truth-telling versus lying, or to make sense of the distinction between history and fiction, or between scholarship and polemics, or between science and pseudo-science (in the context of those sciences which deal with the past).

My point is that using the form of words I did does not necessarily commit me to a particular metaphysical view. One can, I think, use and understand such language and employ such a distinction whilst remaining completely agnostic about the nature of the past: it might be a meaningless concept; it might be a figment of our imaginations; it might be in some sense actual but created and determined, in part or in toto, by us; it might be stable, or it might be shifting and unstable (i.e. dreamlike). Or it might be more or less how the vast majority of humans probably think of it: that is, as existing or having existed quite independently of us and our thoughts and desires; as stable and unalterable; as knowable only imperfectly and in part. Most of the listed options are quite silly, of course, but my point is that you can make the statement I made without necessarily committing to any particular view.

There was a second claim of mine to which Dan took exception, calling it “flat out false… [a]nd obviously so." He elaborated on his objections in an essay and, given that the essay prompted further extensive discussion (more than 160 comments), some may feel that the topic has been done to death. My view, however, is that, some recapitulation and clarification may be useful and help to allay confusion and misunderstanding.

The claim in question [made in the course of online discussion of an essay of mine] was that “the past is what it is (or was what it was).” I could elaborate on what I meant by this but perhaps the best way to unpack the intended meaning without inadvertently bringing in new complications is simply to look at the context in which the claim was made.

A commenter, reacting against my skeptical attitude to the stories historians tell and to my suggestion that we should focus instead on reading for ourselves texts from the past, had queried my use of certain words (‘external’, ‘alien’, ‘arbitrary’) in describing how historians often project their own (political, moral, etc.) preoccupations and values into the stories they tell about the past, preoccupations and values which are often quite alien (as I put it) to the people and societies being described.

“All of these words,” he said, “are puzzling to me: ‘external’, ‘imposing’, ‘alien’, ‘arbitrary’. Consider me unpersuaded.”

“The past is what it is (or was what it was),” I replied. “Our present, from the point of view of the past, does not exist. I am using words like ‘alien’ and ‘external’ to make this point. I assume that we both want to understand the past in its own terms; as it was; distorted as little as possible by present-day preoccupations and perspectives. Thus my concerns (overdone in your estimation) about historians wittingly or unwittingly inserting their own values or the values of their time into the stories they tell."

I said that we want to understand the past “in its own terms” and “as it was.” Taken in isolation I concede that this latter phrase especially could be seen to imply the naive view which Dan ascribes to me. But I explained my meaning in the words which immediately followed: [we want our view to be] “distorted as little as possible by present-day preoccupations and perspectives.”

This is why I recommended focusing on primary sources, reading the actual texts from the past in the languages in which they were written. Will we be able to understand them in exactly the same way their authors understood them? No. Our experiences are very different. But scholars who immerse themselves in the writings of a particular period are able to achieve a very good sense of the perspectives of the original authors.

So when I spoke of the past “as it was” I was not talking about a perspectiveless, abstract or noumenal past at all. I was talking about the actual perspectives of actual people who lived and spoke and wrote and some of whose writings we have access to and are able to read.

There was also some discussion of the very distant past, before the advent of observers. Obviously, envisaging this poses greater problems because you cannot talk about the perspectives of the time, and compare or contrast them with our own. There were no perspectives then.

I want to turn now, albeit briefly, to some broader issues and specifically to a piece written some years ago by Daniel Kaufman entitled “Knowledge and Reality” which came up in the discussions described above. It begins as follows:

“If you were to go to the trouble of asking ordinary people about their views on knowledge and reality – accosting them, at random, on street corners, perhaps – and succeeded in getting honest answers, you would likely discover that they hold something like the following view: What it is to know something is to possess some body of information – to have a “picture” of thing – that squares with or is true to reality. If you were to push further, regarding ‘reality’, they would likely characterize it along the lines of “everything that actually exists” (the ‘actually’ intended to preclude imaginary and fictional things like unicorns and Sherlock Holmes).”

Plausibly, this is what people would indeed say. You could see it as a form of naive realism. But, if my view is (as Dan has suggested) a form of naive realism, it is not this form of naive realism.

The crucial issue here for me is a matter of underlying assumptions and perspective. I see my body as an intrinsic part of the physical world and my “self” as the creation of a (physically instantiated) culture. This culture is just as much a part of reality as anything else.

Cultural products – languages, artworks, nursery rhymes, fiction, music, etc. – undeniably constitute a part of reality; and Sherlock Holmes stories and unicorn legends are part of this reality. Obviously the characters and creatures featured in these stories are not real in the sense that real people or real animals are real (though small infants are unable to grasp this). But, as imagined characters and creatures, they are components of the real (and physically instantiated) cultural matrix in which we happen to exist. A cultural matrix of some kind is, of course, a necessary condition for our existence as persons and for our functioning as human beings.

The world is a single world. (At least I see no reason to think otherwise.) It includes myself and others and language and culture as well as all the fundamental processes upon which physics and other sciences are focused.

Though all worthwhile discourse will (in my opinion) be consistent with the findings of science, it will not necessarily be scientific, even in a broad sense of the word. The trick (as I see it) is to feel the pulse and appreciate the potency of language and other mechanisms of cultural expression without metaphysicalizing these processes in any way. (Without falling for Romantic myths about art and artists, for example.)


[This is an abridged version of an article originally published at The Electric Agora.]