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Posts Tagged ‘Paradigm’

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.

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[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.


– By Byron Jennings, (Ex) Theorist (or is it: once a theorist, always a theorist…) and Project Coordinator

Thomas Kuhn (1922 – 1996) began his career as a physicist but then, as a post-doc, went over to the dark side and became a philosopher. It is for his work on the dark side that he became famous. Normally one assumes that when a scientist starts doing philosophy it is a sign of senility, but in his case it was too early in his career and his insights were actually useful (Yes, philosophy can be useful). His main contribution, in my opinion, was his introduction of the idea of the paradigm. A paradigm is the set of interlocking assumptions and methodologies that define a field of study. It provides the foundation for all work in the field and a common language for discourse. It is the fundamental model for the field and in historical studies is sometimes referred to as the controlling narrative.

If you’ve ever heard the phrase ‘paradigm change,’ you would think that all paradigms do is change. But the idea of the paradigm is actually subversive – it helped undermine the “received view” of what science is and still undermines experimentalist’s attempts to eliminate theory (Which can’t be done, by the way!). Full disclosure: I am, or rather was, a theorist. Administration is even farther to the dark side than philosophy.

The concept of paradigm was introduced in contradistinction to the ideas of positivism that defined the “received view”. The positivists tried to work directly with observations and eliminate all metaphysics or model dependence. Kuhn, on the other hand, claimed the observations themselves are theory laden or model dependent.  You cannot, as a matter of principle, eliminate the metaphysics because the observation, or at least their interpretation, depends on the theory, model, or paradigm.  The paradigm sets the frameworks that gives meaning to the observations and frames the very questions that are considered worthy of addressing.  Examples of paradigms would be Aristotelian physics, classical physics, the standard model of particle physics, or the modern synthesis of evolution.

While paradigms do more than change but they do indeed change and when they do all—oops I cannot say that!—all heck breaks loose. Things one thought one knew and could rely on suddenly go poof. This going ‘poof’ was what the positivists tried and failed to get around by eliminating the models and working directly with the observations.

As Einstein (I like name dropping) pointed out, when paradigms change, it tends to be the most central parts of the previous paradigm that are eliminated. In Aristotelian physics, it was the fixed earth and the perfect heavens that Galileo destroyed with his telescope. Classical mechanics is built on Euclidean three-dimensional space and well-defined trajectories. Special and general relativity eliminated Euclidean geometry, and string theory, if correct, means space is not three-dimensional. Quantum mechanics eliminated the well-defined trajectories. This still causes some people sleepless nights but does not bother me since most of the time I do not know where I am or where I am going anyway. Evolution wrecked havoc with the concept of species. Before continental drift was accepted, a central concept of geology was the fixed continents. The examples are endless.

A side effect of this is that one cannot depend on the contents of the present theories or models to have any direct connection with reality.  The ether (electromagnetism), caloric (heat), phlogiston (fire), and mal air (medicine) that at one time were essential parts of the understanding of how the universe works were eliminated by new improved models. There is no guarantee that the contents of the current models will not be similarly eliminated.  Maybe we will find quarks disappearing or more likely, time, since it is apparently more fundamental.

So what is science and what is it good for if the basic concepts keep changing?  Well now, that is a good question.


– to be continued –