Science and Beauty

Here is an article by Frank Wilczek (a 2004 Nobel Prize in Physics winner) that I ran across a while ago and it gives an interesting look at how science has worked in an area of particle physics dealing with supersymmetry. I really like what he says here because it touches on so many areas of science. It deals with falsificationism, tenacity of theories, scientific progress, philosophical shaping principles (such as beauty), etc. I'd suggest reading the whole article, but I'll give a summary. If you don't know what "supersymmetry" or "gauge symmetry" are, don't worry, the details aren't as important as seeing how science has been (and is) done. Just replace those terms with "Theory X" or "Theory Y" if you have to.

To put it briefly, at one time physicists had very complicated models of supersymmetry. These models were "not wrong" according to Wilczek, but when they published the models he felt some "embarrassment about the complexity and arbitrariness of what we'd come up with."

Later, in an attempt to take a different approach to the problem, they tried to add simplified versions of supersymmetry to the previously more fruitful ideas of gauge symmetry. What they came up with was that the supersymmetric versions gave similar results to the original gauge symmetry theories, even though the models were much different.

That all seems great, except that technically these supersymmetric versions were not correct because they ignored an important part of supersymmetry for the sake of simplicity. But they kept this (technically) wrong model because "it presented a result that was so straight forward and successful that it made the idea of putting gauge symmetry and supersymmetry unification together seem (maybe) right."

Wilczek concludes with: "This little episode, it seems to me, is 179 degrees or so out of phase from Popper's idea that we make progress by falsifying theories. Rather in many cases, including some of the most important, we suddenly decide our theories might be true, by realizing that we should strategically ignore glaring problems."

Recently, John Zimmer at Letters from Babylon has had a couple of posts dealing with the role of aesthetics in science. There are a lot of questions that can be raised about this issue. Why is a beautiful or elegant or simple theory better than a ugly, inelegant, complex theory? How can a scientist justify ignoring data while sticking with a theory that is "beautiful?"

One answer is that the "beauty" criterion is one way to handle the problem of underdetermination of theories. Underdetermination of theories means, according to Del Ratzsch (from Nature, Design, and Science), that "any body of data, no matter how extensive or complete, is always in principle consistent with any number of possible explanatory theories (whether we can think of any or not)." What this means is that empirical data alone cannot logically confirm a theory or "force" a scientist to accept a theory. There are always non-empirical factors that must be taken into consideration. As I said above, "beauty" is one of these non-empirical factors. Other non-empirical factors include explanatory power, coherence, self-consistency, consistency with other basic scientific principles, breadth, accuracy, scientific fruitfulness, historical track-record, and resilience. All of those (non-empirical) factors have played important roles in science and are very often indicators of "good" science.

Let me quote Del Ratzsch, one more time: "[A] simple theory that accounts for the data is widely accepted as more likely true than a wildly complicated theory covering the same data. These values are thus, on this view, neither arbitrary nor subjective, but are truth-relevant, epistemic values, and are thus legitimate within the scope of the larger alethic aims of science." But does this really answer the question of "Why simplicity?" I think it does to the same extent we have answered the questions of "Why explanatory power?" or "Why breadth?" Human beings do science (I know, it seems obvious, but I think it is forgotten a lot when people start talking about the philosophy of science) and these nonempirical factors have some kind of epistemic force behind them, even if we can't explicitly say what that force is.

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