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.

Wittgenstein and Russell on metaphysics, language and science

In his youth, Wittgenstein worked with Bertrand Russell and then subsequently had dealings with the Vienna Circle before taking a rather different direction from the late 1920s on. But the main elements of his thinking remained the same: his distrust of metaphysics, for example. He even came to fault his earlier work (which was heavily influenced by Russell) as being too metaphysical.

A piece I wrote on these themes for The Electric Agora (and subsequently republished here in a slightly revised form) triggered some discussion about the extent to which Russell’s outlook was truly scientific. It was suggested that Russell, driven by unwarranted metaphysical assumptions, got things fundamentally wrong about language and logic. By contrast, the later Wittgenstein and the Oxford school of “ordinary language” philosophy which developed in the 1950’s got things fundamentally right.

In the course of the discussion, I made the point that Russell was committed to a view of the world based on evidence and reason and was an energetic advocate for science and for a scientifically-oriented philosophy. This claim prompted the suggestion that, while Russell’s attitude to science was indeed positive, he made a fetish of science.

There is something in the fetishization idea. As an adolescent Russell had found comfort in the certainties of mathematics. And it takes a particular kind of mentality to be so concerned about the foundations of mathematics as to devote many years to attempting to elaborate a sound logical basis for the discipline.

This story, however, can be told many ways. And it is not just a story about one man’s obsessions. It was a remarkable time in European intellectual circles, and arguably what made it so remarkable was the way that scientific advances in a range of areas – especially historical linguistics, textual criticism, natural history, mathematics and physics – mattered for the general culture. There was a sense that the world had changed irrevocably since the Enlightenment; that it was no longer business as usual. Too many established truths had been shown not to be truths at all. Given this intellectual upheaval, it is no wonder that the new world sensed or foreseen by many 19th-century thinkers and artists was a disturbing and disorientating one.

Despite their various metaphysical commitments or assumptions, I don’t think it plausible to see the likes of Frege and Russell in the same terms as the Hegelian metaphysicians who preceded them, if only because they were committed to scientific methods and open to the possibility that their various projects would fail. They were intellectual pioneers; explorers, not dreamers. And they were bound in a very productive way to the spirit of their time.

The grand plan to create an explicit and complete logical system which could encompass arithmetic was demonstrated – by Kurt Gödel in the early 1930s – to be impossible. But, as Karl Popper pointed out, this is precisely how science works and progresses: by bold conjectures and refutations. Without the prior work by Frege, Russell and others, Gödel would never have come to devise his remarkable proof. And it’s not as if Frege’s and Russell’s work was successful only in this negative sense. After all, their technical achievements helped to lay the groundwork for – and even shaped in certain ways – the revolution in digital computing as well as providing fruitful ideas in specific areas (such as formal linguistics).

I certainly don’t want to mount a defense of Russell’s logical atomism. I see the whole project of trying to construct a perfectly clear and perspicuous language (even if it is meant only for scientific purposes) as being doomed to failure. Russell’s own views changed over time. In his later works, he defends an approach to human knowledge which is (in my opinion) eminently defensible.

Russell was drawn to a correspondence view of truth. And, though his original insistence on a structural isomorphism between language and the world may not be sustainable, it seems to me (as it did to figures as different as Karl Popper and J.L. Austin) that there are objectively existing states of affairs – in both ordinary and scientific contexts – to which most statements refer and against which their truth or correctness (or whatever term might be appropriate) depends.

I see this view (or something very like it) as a prerequisite for science and scholarship as those pursuits have been traditionally understood. Sure, such a view has been challenged by various forms of idealism and radical epistemologies over the years. It is currently under sustained attack. Is it worth defending? Absolutely. How one sees these matters has serious intellectual, cultural and even political consequences.

Much of Austin’s work is descriptive and classificatory and, as I understand it, Austin saw himself as doing something like proto-science. He believed that his work on language would eventually form the basis for a mature science, and indeed his work has been picked up by linguists as well as by philosophers. Austin’s intellectual orientation was clearly quite different from Wittgenstein’s. Both thinkers had an appreciation of the power, complexity and expressiveness of natural language. But Wittgenstein was not interested in the sort of painstaking explicitness and classificatory thoroughness to which Austin aspired.

Previously I contrasted Russell’s scientific view of the world with Wittgenstein’s view. I am now suggesting a similar (but more limited) contrast between Austin and Wittgenstein. I want to make it clear, however, that I am not taking sides with respect to the thinkers involved. There is value both in Wittgenstein’s and in Austin’s writings on language. It’s just that their respective approaches and orientations are different.

On Russell and Wittgenstein, there are some issues on which I side with one, and some issues on which I side with the other. With respect to the status of science and scientific knowledge I am very much in Russell’s camp, not Wittgenstein’s.