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Byron Jennings | TRIUMF | Canada

View Blog | Read Bio

Has there ever been a paradigm shift?

Yes, once!

Paradigm and paradigm shift are so over used and misused that the world would benefit if they were simply banned.  Originally Thomas Kuhn (1922–1996) in his 1962 book, The Structure of Scientific Revolutions, used the word paradigm to refer to the set of practices that define a scientific discipline at any particular period of time. A paradigm shift is when the entire structure of a field changes, not when someone simply uses a different mathematical formulation. Perhaps it is just grandiosity, everyone thinking their latest idea is earth shaking (or paradigm shifting), but the idea has been so debased that almost any change is called a paradigm shift, down to level of changing the color of ones socks.

The archetypal example, and I would suggest the only real example in the natural and physical sciences, is the paradigm shift from Aristotelian to Newtonian physics. This was not just a change in physics from the perfect motion is circular to an object either is at rest or moves at a constant velocity, unless acted upon by an external force but a change in how knowledge is defined and acquired. There is more here than a different description of motion; the very concept of what is important has changed. In Newtonian physics there is no place for perfect motion but only rules to describe how objects actually behave. Newtonian physics was driven by observation. Newton, himself, went further and claimed his results were derived from observation. While Aristotelian physics is broadly consistent with observation it is driven more by abstract concepts like perfection.  Aristotle (384 BCE – 322 BCE) would most likely have considered Galileo Galilei’s (1564 – 1642) careful experiments beneath him.  Socrates (c. 469 BC – 399 BC) certainly would have. Their epistemology was not based on careful observation.

While there have been major changes in the physical sciences since Newton, they do not reach the threshold needed to call them a paradigm shifts since they are all within the paradigm defined by the scientific method. I would suggest Kuhn was misled by the Aristotle-Newton example where, indeed, the two approaches are incommensurate: What constitutes a reasonable explanation is simply different for the two men. But would the same be true with Michael Faraday (1791 – 1867) and Niels Bohr (1885–1962) who were chronologically on opposite sides of the quantum mechanics cataclysm?  One could easily imagine Faraday, transported in time, having a fruitful discussion with Bohr. While the quantum revolution was indeed cataclysmic, changing mankind’s basic understanding of how the universe worked, it was based on the same concept of knowledge as Newtonian physics. You make models based on observations and validate them through testable predictions.  The pre-cataclysmic scientists understood the need for change due to failed predictions, even if, like Albert Einstein (1879 – 1955) or Erwin Schrödinger (1887 – 1961), they found quantum mechanics repugnant. The phenomenology was too powerful to ignore.

Sir Karl Popper (1902 – 1994) provided another ingredients missed by Kuhn, the idea that science advances by the bold new hypothesis, not by deducing models from observation. The Bohr model of the atom was a bold hypothesis not a paradigm shift, a bold hypothesis refined by other scientists and tested in the crucible of careful observation. I would also suggest that Kuhn did not understand the role of simplicity in making scientific models unique. It is true that one can always make an old model agree with past observations by making it more complex[1]. This process frequently has the side effect of reducing the old models ability to make predictions. It is to remedy these problems that a bold new hypothesis is needed. But to be successful, the bold new hypothesis should be simpler than the modified version of the original model and more crucially must make testable predictions that are confirmed by observation. But even then, it is not a paradigm shift; just a verified bold new hypothesis.

Despite the nay-saying, Kuhn’s ideas did advance the understanding of the scientific method. In particular, it was a good antidote to the logical positivists who wanted to eliminate the role of the model or what Kuhn called the paradigm altogether. Kuhn made the point that is the framework that gives meaning to observations. Combined with Popper’s insights, Kuhn’s ideas paved the way for a fairly comprehensive understanding of the scientific method.

But back to the overused word paradigm, it would be nice if we could turn back the clock and restrict the term paradigm shift to those changes where the before and after are truly incommensurate; where there is no common ground to decide which is better. Or if you like, the demarcation criteria for a paradigm shift is that the before and after are incommensurate[2]. That would rule out the change of sock color from being a paradigm shift. However, we cannot turn back the clock so I will go back to my first suggestion that the word be banned.

To receive a notice of future posts follow me on Twitter: @musquod.


[1] This is known as the Duhem-Quine thesis.

[2] There are probably paradigm shifts, even in the restricted meaning of the word, if we go outside science. The French revolution could be considered a paradigm shift in the relation between the populace and the state.


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  • Lamont Granquist

    If eliminating the concept of the aether and setting the speed of light to be constant irrespective of the reference frame of the observer isn’t a “paradigm shift”, then I think you’ve gone way too far in the other direction and made the bar so high that “paradigm” is equally useless with that strong of a definition.

  • http://www.triumf.ca/theory/byron-jennings Byron

    High indeed, but it is Kuhn’s own criteria for what constitutes a paradigm shift. Everyone agrees that classical mechanics could not describe atomic structure and quantum mechanics could. The introduction of classical mechanics from Aristotelian was even bigger. The question there was how to obtain knowledge. Was it worth while to look through the telescope?

  • http://transcyberphysix.blogspot.fr laboussoleestmonpays

    From wiki : “When enough significant anomalies have accrued against a current paradigm, the scientific discipline is thrown into a state of crisis, according to Kuhn. During this crisis, new ideas, perhaps ones previously discarded, are tried. Eventually a new paradigm is formed.

    Personal interpretation:
    present paradigm : Standard Model of particle physics and standard model of cosmology
    anomalies : Higgs unnaturalness, dark matter and dark energy conundrum …
    new idea : “attomization” of spacetime (Higgs mass or its associated vacuum energy value coincides roughly with the attoscale), I mean a fresh mathematical set up and new physical ideas to really deal with the noncommutative nature of the quantum word, not only matter and radiation but spacetime as well.

    I think to appreciate a paradigm shift one needs to contemplate a very long period of time, the atomic and relativistic revolution has not yet been completed. This is probably why there is no consensus yet for the existence of a new paradigm shift since Galileo/Newton. I do think we could appreciate the quantum paradigm shift these days but a simpler explanation requires quite elaborate concepts and “an electron is more difficult to apprehend that the diagonal of a triangle” as a mathematician wrote once.
    And to end with, it is definitely worth today to look through a spectroscope not a telescope!

  • http://www.mazepath.com/uncleal/qz4.htm Uncle Al

    Vacuum is isotropic. Noether’s theorems couple symmetry to angular momentum conservation. Two underlings said mirror symmetry is testably untrue[1]. Arms were twisted for funding[2]. The impossible result was confirmed[3]. Particle physics was paradigm-shifted. This discovery was discarded for being impossible 28 years earlier[4].

    Parity violations, chiral anomalies, symmetry breakings; Chern-Simons repair of Einstein-Hilbert action, empirically grotesque string /M-theory, SUSY/MSSM; unending epicycles of parameterizations. Dark matter doesn’t exist[5]. Vacuum is trace chiral anisotropic toward fermionic matter (quarks). The impossible is testable.

    Opposite shoes chiral vacuum embed (mount a left foot) with different energies. They vacuum free fall along divergent minimum action trajectories – Equivalence Principle (EP) violation. Crystallography’s 11 pairs of enantiomorphic space groups are 11 perfect pairs of opposite shoes self-similar from cm^3 down to one unit cell. Two geometric Eötvös experiments: 0.113 nm^3 volume/α-quartz unit cell. 40 grams net as 8 single crystal test masses compare 6.68×10^22 pairs of opposite shoes (pairs of enantiomorphic unit cells). γ-Glycine runs in kind[6].

    Science boasting paradigm-shifting observations now declares “six impossible things before breakfast” are “nekulturny.” Trace vacuum chirality leaks angular momentum conservation as Milgrom acceleration, ending dark matter. Shift a paradigm in 90 days. Look.

    [1] Phys. Rev. 104(1) 254 (1956), http://prola.aps.org/pdf/PR/v104/i1/p254_1
    [2] Phys. Rev. 105(4) 1413 (1957), http://prola.aps.org/pdf/PR/v105/i4/p1413_1
    [3] Phys. Rev. 105(4) 1415 (1957), http://prola.aps.org/pdf/PR/v105/i4/p1415_1
    [4] PNAS 14(7) 544 (1928), http://www.pnas.org/content/14/7/544.full.pdf+html
    [5] arXiv:1310.8214, 1306.5534, 1306.3983
    [6] http://www.mazepath.com/uncleal/erotor1.jpg

  • Tienzen (Jeh-Tween) Gong

    @Byron Jennings,
    You bar is not high but is correct. Yet, even if your wish (However, … so I will go back to my first suggestion that the word be banned) comes true, there will still be paradigm shift in the future. Although I do agree with your *definition* 100%, I would like to paraphrase it with four point list definition; thus, I can go beyond your definition. *Paradigm* encompasses 4 points (or parts).
    i. It has a preconceived *Belief* which is the foundation for the epistemology. For Aristotelians, they believed that the *new* knowledge can be judged by the *reasoning* (logic and a body of old knowledge) power alone. For Newtonians, they *Believe* that the new knowledge is accepted if and only if it is observational testable (by man with gadgets).
    ii. It is exclusive (my way or the highway). Thus, Newtonian paradigm kills *rationale* by crowning it with a title of *Speculative*. For example, the Alpha (electron fine structure constant) is only a pure simple number. The equation below can calculate it precisely, and its correctness can be verified by any 8th grade kids who knows no physics. But, it will simply be ignored by the physicists as they lack the ability to come up an observational test for it.
    Beta = 1/alpha = 64 ( 1 + first order mixing + sum of the higher order mixing)
    = 64 (1 + 1/Cos A(2) + .00065737 + …)
    = 137.0359 …
    A(2) is the Weinberg angle, A(2) = 28.743 degree
    The sum of the higher order mixing = 2(1/48)[(1/64) + (1/2)(1/64)^2 + …+(1/n)(1/64)^n +…]
    = .00065737 + …
    iii. It is a sociological-dependent-reality, that is, it is not absolute but is *selective*. The M-string theory and SUSY are all *speculative* but are still all viewed as the great physics, a big part of the current *Paradigm*.
    iv. It must be accepted by the mainstream community, regardless of it being right or wrong.

    Your definition emphasizes only the first one of the four points.

  • NA

    There is a historian of science who goes a little further than you and dismisses the whole notion entirely. The first post lays out his criticisms of Kuhn & the second one is more directly related to Newton, pointing out that Aristotelian physics was already on the wane by the time he rolled around.



    Interesting if your interested.

  • jfb2252

    I think the the change in biology from Linnaeus to evolution was a paradigm shift as you define Kuhn’s distinction.

  • http://www.archidevsys.co.nz Gavin Flower

    I wonder if the postings from ‘Uncle Al’ are actually computer generated Scientific Gobbledegook!

  • http://www.archidevsys.co.nz Gavin Flower

    I think the principle of superposition in quantum mechanics qualifies a paradigm shift that has not yet been completed. The idea that something can exist in two or more different states at the ‘same time’ is totally alien to the way most people consider the ‘Real’ world.

    Another potential paradigm shift would occur once the notion that ‘Time’ is fundamental is overthrown, assuming that at least one of the theories that postulate that become widely accepted. This puts a new twist in the argument of ‘Freewill’ versus ‘Determinism’.

    There is still a bitter fight over the paradigm that the Universe was not created by one or more Gods. Note that far too many people still insist that a ‘God’ created all species and actively promote illogical & fallacious arguments in attempting to support their position.

  • http://www.triumf.ca/theory/byron-jennings Byron

    He frequently comments on my posts and I always wonder if I should reject it. But you may be correct.

  • http://www.triumf.ca/theory/byron-jennings Byron

    It could be. That was part of the change that brought biology into science.

  • http://www.triumf.ca/theory/byron-jennings Byron

    Newton and Aristotle are to some extent end points. There was a lot happening in a number of fields around 1600. Galileo and other laid the foundation that Newton built on.

    Kuhn got a lot wrong but his idea that the framework was necessary to interpret observations was a needed counter balance to the logical positivists.

    Thanks for the links

  • Lukas

    “But back to the overused word paradigm, it would be nice if we could turn back the clock and restrict the term paradigm shift to those changes where the before and after are truly incommensurate; where there is no common ground to decide which is better.”

    Why would we? The problem is not the concept of paradigms, but with the meaning of ‘incommensurable’. Incommensurability is a result of paradigms, it’s not part of the definition.
    People assume incommensurability is an absolute – all or nothing. This is not something Kuhn says, nor something that historians and philosophers say today.

    In any case, Kuhn’s theory is still being fruitfully applied in the history of science. In my opinion, that is the most important factor in evaluating philosophy of science.

  • http://www.triumf.ca/theory/byron-jennings Byron

    Incomprehensibility play a large role in Kuhn’s and also Feyerabend’s understanding of science. They used it to claim that there was no objective criteria to say that the post paradigm shift framework was better than the pre paradigm shift framework. Since the scientific revolution effectively changed the definition of knowledge, this argument has some validity for the change from Aristotelian to Newtonian physics. It has no validity for the change from Newtonian mechanics to quantum mechanics.

  • Tienzen (Jeh-Tween) Gong

    Paradigm is, in fact, the most urgent issue of today in physics.

    In addition to being a conceptual terminology in Philosophy of Science, *paradigm* is a living organism (with birth, youth, aging and death). The preconceived belief is its DNA, distinguishing its species type. The attributes of exclusiveness, selectiveness and consensus are the life-force during its youth for a very healthy growth and are also the force for its aging, especially by growing the malignant cancerous growths. Then, there are external forces which give the aged paradigm a deadly blow to end its life.

    For the Aristotelian paradigm, its nutrients (the body of old knowledge) were too weak and often not correct. Thus, it was easily killed by the new external force of Newtonian methodology. Yet, although the Newtonian paradigm ousted the * Aristotelian rationale* by crowning it with a title of *Speculative*, *rationale* itself remains as the key engine in the Newtonian methodology.

    Besides a foundation (the DNA, the backbone and its nutrients), a paradigm does fill up with fleshes (the contents, such as the General Relativity, Quantum Mechanics, Standard Model, etc.). Yet, at the same time, it can have some growths which are beyond the reach by its foundation. For the Newtonian paradigm, there are at least three such growths.
    i. Model sub-paradigm — most of physicists today do not believing in *truth* as it is too elusive, and they claims to be only the *model builders*. Yet, there are many different models, for Bobbie doll, for airplane, for Empire State Building, etc.. Every model is modeling an *object* (the reality or the underlying Truth). For scientific model which has no underlying truth (or not sure about what it is), it could often turn out to be a model for Mickey Mouse. How can anyone build a model while not knowing what he is modelling? Even if the truth is very elusive, the modeler must make a wild-guess for it. Anyway, this Model sub-paradigm is slowly drifting away from the Newtonian paradigm.
    ii. Multiverse — Multiverse is not yet a new paradigm but is a major *flesh* of the current physics paradigm. But, multiverse as a *reality*, it articulated or manipulated an observable universe which we are living in. But, multiverse as a *theory*, it *fails* to pin point the nature’s way of manipulation which is a reality. Thus, Multiverse is either a new coming paradigm or a failed theory. Furthermore, by definition, multiverse is beyond the reach of the Newtonian methodology.
    iii. SUSY — it was the center *flesh* of the current physics paradigm for over 40 years. After receiving many deadly blows recently, its devotees are desperately transforming it into a religious-like “the hope of SUSY parousia”, by pushing it out of the reach of this Newtonian paradigm.

    With the three growths above, the Newtonian paradigm is at its last breath and is about ready to kick the bucket. The Aristotelian paradigm was ousted because of its weak *body of knowledge*, but its *rationale* is still the engine (not criterion) in the Newtonian paradigm. In a sense, the *rationale* is immortal, much more powerful than the Newtonian methodology which has run out of its breaths as the technology *might be* no longer able to reach the last courtyard of nature. On the other hand, today, the *body of knowledge* (General Relativities, Quantum Mechanics, Standard Model, Planck data, etc.) is weak no more. This solid body of knowledge forms a set of anchors. Matching those anchors from a *rational framework* (its base MUST contains no known physics) can become the criterion of a new paradigm. Thus, today, we have two new paradigms around the corner.
    One — the hope-of-parousia paradigm, pushing SUSY and multiverse beyond the reach of Newtonian mythology.

    Two — the rationale/anchor-matching paradigm.

  • Lukas

    “They used it to claim that there was no objective criteria”

    That was not Kuhn’s claim. The claim was that the arguments for a paradigm switch can never be fully cast into a logical deductive form.

    In any case it does not change anything from a pragmatic point of view. As long as paradigms are helpful in studying science history, they should not be ‘banned’.

    Science history and philosophy of science before Kuhn’s intervention was extremely unrealistic. From a pragmatic point of view; why would we ever want to go back to those times? History of Science is more alive and healthy than ever. And a lot of that is thanks to Kuhn.

  • Bob

    Dear Byron,

    thanks for the post. Overall I generally agree with you here (although i have not read Kuhn), and very much enjoyed reading this.

    One question for you (which Tienzen also mentions) is this: how would you characterize the multi-verse proposal? Or more generally the anthropic vs dynamical explanation for things. IF (and I am not saying it is), but IF it is true that some features of the universe, such as the value of the cosmological constant or the electroweak scale, are determined not by dynamics, but by selection effects, and we are in a multi-verse where we just live in a small corner where we can live…If this is the new way to explain some features of the universe – would you call this a “paradigm shift”?

  • http://www.triumf.ca/theory/byron-jennings Byron

    The multi-verse hypothesis and the god did it hypothesis have a lot in common. They both can explain anything but make no predictions. Definite predictions are the hallmark of science.

  • Bob

    Well if the multiverse theory is not part of the current “hallmark of science”, then surely the multiverse would be a “paradigm shift”.

    By the way, comparing multiverse with god is pretty unfair. For instance, a “simple” multiverse arises if one just has a scalar field with a potential with multiple minima (even the Higgs potential can give that due to RG evolution); this has nothing to do with god, but just an application of QFT to scalars.

  • Bob

    Actually in 1987 weinberg used the multiverse hypothesis to predict the existence and value of the cosmological constant. This prediction was later confirmed in 1998. I think it is silly to say that the god hypothesis could do the same. Else, are you saying weinberg does not do science? (This would be a strange point of view regarding what many ppl believe to be the greatest living physicist).

  • http://www.triumf.ca/theory/byron-jennings Byron

    His argument did not rely on the multiverse rather he argued from the current state of the universe what the cosmological constant should be.

  • Bob

    That’s completely false. Weinberg did not just put an observational bound on the cosmological constant. He asked: what would its value be if it was purely determined randomly from a multiverse. He said it should be small enough that galaxies can form, BUT, it should not be much smaller than this, i.e., the cosmological constant should currently be a significant fraction of the energy density of the universe. In 1998, we found it, and it is about 70%. You cannot possibly conclude it should be as large as possible, but no larger, than what it should be for galaxies to form (and life to exist) then unless you are using STATISTICAL reasoning from a multiverse. Did you even read the paper?

  • Bob

    Also, I notice you completely avoided my central question: as to whether you define this as a paradigm shift. I think it does. But like any paradigm shift there are many people (such as yourself) who will just cling to the old fashioned way of business as usual, rather than moving towards the correct description as nature is indicating. Instead of accepting nature as it is, there are always people, such as yourself, who throw out things like “thats not science”… and weinberg doesn’t do science when he talks about multiverse. these attitudes have never been useful. the only unscientific thing is to ignore nature, when she gives us clues, whether it is multiverse or otherwise.