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Philosophy & Science

Einstein vs Logical Positivism

Rossen Vassilev Jr. asks if modern physics has become too metaphysical.

Logical positivism was a philosophical movement of the 1920s and 30s which wanted to introduce the methodology of science and mathematics to philosophy. As part of this ambition, the Vienna Circle (Wiener Kreis in German) of logical positivists tried to purge philosophy of metaphysics – by which they meant any speculation that could not be tested using the methods of modern empirical science. The members of the Vienna Circle, including its nominal leader Moritz Schlick, found the speculative claims of traditional metaphysics, especially those based on religion, to be false, uncertain, or sterile. For Rudolph Carnap, another influential member of the Circle, “the (pseudo)statements of metaphysics do not serve for the description of states of affairs.” They are, like poetry and music, “in the domain of art and not in the domain of theory” (from ‘The End of Metaphysics?’ in Western Philosophy: An Anthology, edited by John Cottingham). Carnap confidently proclaimed that in the Circle’s new materialist philosophy of science, “a radical elimination of metaphysics is attained, which was not yet possible from the earlier anti-metaphysical standpoints.”

In fact, the logical positivists dismissed all non-scientific speculation altogether, not just in philosophy, insisting that all statements and theories are literally meaningless unless they can be logically verified or checked by experiment or observation. This is the so-called verification principle. A.J. Ayer was not a member of the Vienna Circle, but was powerfully influenced by it, and sprang its ideas upon the English-speaking world with his book Language, Truth and Logic. He argued that every verifiable proposition is meaningful (though it may be either true or false), and any unprovable claim, whether about science or metaphysics or the existence of God, is meaningless. Claims about ethics, he said, are also unverifiable so their only meaning can be as expressions of our emotional attitudes. According to verificationism, the meaning of any statement lies in its method of verification.

Soon, Karl Popper in his Logic of Scientific Discovery pointed out a problem with verification: no number of observations that agree with a theory can ever conclusively prove it true. A classic example is the claim that “all swans are white.” Not even a large number of sightings of white swans will prove this true, but even a single sighting of a non-white swan will disprove it (‘falsify it’). He argued that a “theory which is not refutable by any conceivable event is non-scientific. Irrefutability is not a virtue of a theory (as people often think) but a vice… the criterion of the scientific status of a theory is its falsifiability, or refutability, or testability.” So for Popper falsifiability, not verifiability, is the test which distinguishes genuine science from what Popper called ‘pseudo-science’ – or ‘metaphysics’.

In the second of four BBC interviews with Bryan Magee about logical positivism and its legacy, A.J. Ayer stressed that the Vienna Circle’s members “saw Einstein’s work on relativity and also the new quantum theory as a vindication of their approach.” It does seem that the replacement of Newtonian physics by Albert Einstein’s general theory of relativity had a revolutionary impact on logical positivism. As John Earman writes, “a brief examination of the actual history of logical positivism reveals that one of its most fundamental inspirations is precisely this Einsteinian revolution. The early writings of the logical positivists – of Schlick, Reichenbach, and Carnap, in particular – all focus on the theory of relativity, a theory whose revolutionary impact is explicitly recognized in the course of a polemic against their philosophical predecessors.” (Inference, Explanation and Other Frustrations, p.85, 1992)

But does the revolution in physics that Einstein began in 1905 really vindicate the principles of logical positivism? My contention is that it contradicts the Vienna Circle’s philosophy, particularly the Circle’s near fanatical commitment to the empiricist methodology of David Hume, Ernst Mach and Bertrand Russell, as well as Moritz Schlick’s principle of verifiability. Specifically, although many of the ground-breaking and highly exotic ideas coined by Einstein’s scientific successors – such as white holes, wormholes, dark matter, dark energy, subatomic strings, parallel universes, hidden dimensions of spacetime, and gravitational waves – may appear in the mathematical equations and calculations of theoretical physicists, in most cases no evidence has yet been found in the observable Universe to confirm their existence.

Illustration © Jaime Raposo 2019. To see more of his art, please visit jaimeraposo.com

Metaphysical Philosophy or Science Fiction?

According to renowned physicist Lee Smolin, co-founder of Canada’s Perimeter Institute for Theoretical Physics, this current move of physics away from Vienna Circle-style empiricism is due to “the triumph of a particular way of doing science that came to dominate physics in the 1940s. This style… favors virtuosity in calculating over reflection on hard conceptual problems” (The Trouble with Physics, 2006, pp.xxii). Mirroring the logical positivists’ devotion to empiricism, Smolin is highly skeptical of this ‘particular way of doing science’. It has led to what he calls ‘the current crisis’ in fundamental physics:

“New theories have been posited and explored, some in great detail, but none has been confirmed experimentally. And here is the crux of the problem: In science, for a theory to be believed, it must make a new prediction – different from those made by previous theories – for an experiment not yet done. For the experiment to be meaningful, we must be able to get an answer that disagrees with that prediction. When this is the case, we say that a theory is falsifiable – vulnerable to being shown false. The theory also has to be confirmable; it must be possible to verify a new prediction that only this theory makes. Only when a theory has been tested and the results agree with the theory do we advance the theory to the ranks of true theories”
(The Trouble with Physics p.xiii)

In the light of this, many of the theories embraced by theoretical physicists today look like what Smolin calls ‘metaphysical fantasies’. One of the most prominent is the idea of multiple universes, also known as the ‘many-worlds hypothesis’ or ‘multiverse’ theory. Different versions of it have been promoted as an answer to puzzles in many branches of physics; it was the subject of an entire issue of New Scientist magazine in 2011, and among its many scientific supporters was the late Stephen Hawking, who worked on it in his last published paper. But in spite of all this, the multiverse hypothesis remains a purely speculative theory in the sense of not being checkable by direct observation. In fact it has no concrete empirical evidence to back it up. It cannot be proven using Schlick’s principle of verifiability; nor can it be falsified empirically in the way that Karl Popper believed any truly scientific theory should be. As a mere artifact of theoretical speculation and/or of mathematical models, it is more philosophy and metaphysics than testable empirical science. It borders on science fiction.

Another dubious theory gained popularity as a result of problems surrounding the Big Bang theory, concerning the relatively even distribution of matter observed throughout the visible Universe. This is something one would hardly expect to result from a gigantic explosion of energy concentrated into a point far smaller than an atom some 13.8 billion years ago. But our earliest radioastronomical ‘baby picture’ of how the Universe looked 380,000 years or so after the Big Bang, shows an even distribution of matter in every direction. To explain this anomaly, Alan Guth and other cosmologists proposed the so-called ‘inflation’ theory, according to which the newly created Universe initially expanded at a rate much faster even than the speed of light for a fraction of a second just after the Big Bang. But this ad hoc adjustment or ‘theoretical crutch’ (to use Thomas Kuhn’s apt phrase) fails to explain the even distribution of matter throughout the Universe, because the debris of a Big Bang-like explosion should still be rather unevenly and chaotically spread even if the Universe initially grew incredibly fast. Additionally, the new theory created other complications such as eleven dimensions of spacetime, countless Big Bangs and, again, the existence of numerous copies of each of us inhabiting multiple parallel universes. Smolin remarks that, “The theory of inflation made predictions that seemed dubious” (p.xi), and complained that this is hardly the stuff of which Popperian science is made:

“This is a sleight of hand by which they hope to convert an explanatory failure into an explanatory success. If we don’t understand… our universe, just presume our universe is a member of an infinite and unobservable ensemble of universes… There is so much wrong with this as a scientific hypothesis… it is hard to see how it could make any falsifiable predictions for doable experiments.”
(quoted by John Horgan in Scientific American, January 4, 2015)

Moreover, consider what is perhaps the most popular theory among theoretical physicists today: string theory. According to Smolin, string theory “proposes that all the elementary particles arise from the vibrations of a single entity – a string” which is so infinitesimal that it is invisible even to the super-sophisticated instruments of modern science. But Smolin repudiates the scientific status of string theory because it “makes no new predictions that are testable by current – or even currently conceivable – experiments… Thus, no matter what the experiments show, string theory cannot be disproved. But the reverse also holds: no experiment will ever be able to prove it true” (The Trouble with Physics, p.xiv). Smolin also sees other equally fatal flaws in string theory. “Part of the reason string theory makes no new predictions is that it appears to come in an infinite number of versions… every single one disagrees with the present experimental data” (Ibid). He goes on to demystify the metaphysical claims of string theory despite its clearly dominant position in the world of physics today. “String theory… posits that the world is fundamentally different from the world we know. If string theory is right, the world has more dimensions and many more particles and forces than we have so far observed. Many string theorists talk and write as if the existence of these extra dimensions and particles were an assured fact, one that no good scientist can doubt. More than once, a string theorist has said to me something like ‘But do you mean you think it’s possible that there are not extra dimensions?’ In fact, neither theory nor experiment offers any evidence at all that extra dimensions exist.” (p.xvi)

Fundamental physics has been taken as the model for how all other sciences should develop. For dedicated empiricists like Smolin, it’s a tragedy that “despite our best efforts, what we know for certain about [fundamental physical] laws is no more than what we knew back in the 1970s” (p.viii). He blames this on the ‘arrogance’ of many of the string theorists. (p.269)

It Is ‘All In The Math’?

During the total solar eclipse in the fall of 1919, British astrophysicists observed evidence that the Sun’s gravity bends the path of the light from other stars, confirming a key prediction of Einstein’s general theory of relativity. An insightful article by Richard Panek in the science magazine Discover in March 2008 described how Einstein interrupted a student who was trying to congratulate him for this scientific success, saying “But I knew the theory is correct.” But what, the student asked, if the observations had contradicted his calculations? Einstein replied, “Then I would have been sorry for the dear Lord – the theory is correct.” It’s a smug rejection of the positivist principle of empirical verifiability. Einstein declared years later that “Our experience hitherto justifies us in believing that nature is the realization of the simplest conceivable mathematical ideas. I am convinced that we can discover by means of purely mathematical constructions the concepts and the laws connecting them with each other.” Panek nicely sums up the momentous implications of the leap from the more traditional method of empirical observation to Einstein’s faith in thought experiments and the ‘mathematical imagination’. “For thousands of years, researchers had studied the behavior of the heavens and sought to capture it in mathematical terms. Einstein reversed the challenge: he sought truth in equations and then trusted that studies of the heavens would back him up. Almost all of modern cosmology and theoretical physics follows from that leap of faith – or leap, perhaps, of reason.”

Smolin is not buying any such ‘leap of reason’ – unless it’s backed up by solid empirical evidence: by observations and experiments that prove or disprove any proposed hypothesis in strict compliance with both the Vienna Circle’s philosophy of science and Popper’s insights. He writes, “once you reason like this, you lose the ability to subject your theory to the kind of test that the history of science shows over and over again is required to winnow correct theories from beautiful but wrong ones. To do this, a theory must make specific and precise predictions that can either be confirmed or refuted. If there is a high risk of disconfirmation, then confirmation counts for a lot. If there is no risk of either, then there is no way to continue to do science” (The Trouble with Physics, p.169).

Non-Positivist Conclusions

So is the theoretical physics embraced by today’s heirs to Einstein testable empirical science, metaphysical philosophy, or science fiction? Einstein’s heirs seem to have forgotten Einstein’s words of caution in 1933, that “Experience remains, of course, the sole criterion of the physical utility of a mathematical construction.” Lee Smolin adds his own warning: “Mathematics is our most useful tool, but the idea that it should be prophetic has done a lot of harm.” (Scientific American, January 4, 2015)

Panek’s Discover article concludes by identifying the enormous challenges faced by the troubled field of cosmology, which is now driven more by mathematics-based theory and ‘mathematical beauty’ than by hard-nosed observation-based empiricism. “These latest concepts all exist beautifully in the mathematics, but so far observers have identified no sign of them in the real world… How to move beyond slavish devotion to experience may have been Einstein’s greatest gift to the 20th century. How to bring mathematical imagination back down to earth may rate as his greatest challenge to the 21st.” If this challenge is not faced, then future achievements in fundamental physics – a field which is clearly “suffering from a surfeit of imagination and a deficit of data” (Horgan) – may move ever further from observation and testable prediction into ever more fanciful realms of metaphysical speculation. After all, what is one to think when America’s best-known living cosmologist, Dr Neil deGrasse Tyson, following the philosopher Nick Bostrom, says that the likelihood of the Universe being a digital simulation “may be very high… And if that’s the case, it is easy for me to imagine that everything in our lives is just the creation of some other entity for their entertainment.” Indeed, is this ‘simulation hypothesis’ itself a scientific theory, or pure science fiction?

Rossen Vassilev is studying at Ohio University, in Athens, Ohio.