Building Intuitions on Non-empirical Arguments in Science

Link: https://slatestarcodex.com/2019/11/06/building-intuitions-on-non-empirical-arguments-in-science/

Aeon: Post-Empirical Science Is An Oxymoron And It is Dangerous:

There is no agreed criterion to distinguish science from pseudoscience, or just plain ordinary bullshit, opening the door to all manner of metaphysics masquerading as science. This is 'post-empirical' science, where truth no longer matters, and it is potentially very dangerous.

It's not difficult to find recent examples. On 8 June 2019, the front cover of New Scientist magazine boldly declared that we're 'Inside the Mirrorverse'. Its editors bid us 'Welcome to the parallel reality that's hiding in plain sight'. […]

[Some physicists] claim that neutrons [are] flitting between parallel universes. They admit that the chances of proving this are 'low', or even 'zero', but it doesn't really matter. When it comes to grabbing attention, inviting that all-important click, or purchase, speculative metaphysics wins hands down.

These theories are based on the notion that our Universe is not unique, that there exists a large number of other universes that somehow sit alongside or parallel to our own. For example, in the so-called Many-Worlds interpretation of quantum mechanics, there are universes containing our parallel selves, identical to us but for their different experiences of quantum physics. These theories are attractive to some few theoretical physicists and philosophers, but there is absolutely no empirical evidence for them. And, as it seems we can't ever experience these other universes, there will never be any evidence for them. As Broussard explained, these theories are sufficiently slippery to duck any kind of challenge that experimentalists might try to throw at them, and there's always someone happy to keep the idea alive.

Is this really science? The answer depends on what you think society needs from science. In our post-truth age of casual lies, fake news and alternative facts, society is under extraordinary pressure from those pushing potentially dangerous antiscientific propaganda – ranging from climate-change denial to the anti-vaxxer movement to homeopathic medicines. I, for one, prefer a science that is rational and based on evidence, a science that is concerned with theories and empirical facts, a science that promotes the search for truth, no matter how transient or contingent. I prefer a science that does not readily admit theories so vague and slippery that empirical tests are either impossible or they mean absolutely nothing at all.

As always, a single quote doesn't do the argument justice, so go read the article. But I think this captures the basic argument: multiverse theories are bad, because they're untestable, and untestable science is pseudoscience.

Many great people, both philosophers of science and practicing scientists, have already discussed the problems with this point of view. But none of them lay out their argument in quite the way that makes the most sense to me. I want to do that here, without claiming any originality or special expertise in the subject, to see if it helps convince anyone else.

II.

Consider a classic example: modern paleontology does a good job at predicting dinosaur fossils. But the creationist explanation – Satan buried fake dinosaur fossils to mislead us – also predicts the same fossils (we assume Satan is good at disguising his existence, so that the lack of other strong evidence for Satan doesn't contradict the theory). What principles help us realize that the Satan hypothesis is obviously stupid and the usual paleontological one more plausible?

One bad response: paleontology can better predict characteristics of dinosaur fossils, using arguments like "since plesiosaurs are aquatic, they will be found in areas that were underwater during the Mesozoic, but since tyrannosaurs are terrestrial, they will be found in areas that were on land", and this makes it better than the Satan hypothesis, which can only retrodict these characteristics. But this isn't quite true: since Satan is trying to fool us into believing the modern paleontology paradigm, he'll hide the fossils in ways that conform to its predictions, so we will predict plesiosaur fossils will only be found at sea – otherwise the gig would be up!

A second bad response: "The hypothesis that all our findings were planted to deceive us bleeds into conspiracy theories and touches on the problem of skepticism. These things are inherently outside the realm of science." But archaeological findings are very often deliberate hoaxes planted to deceive archaeologists, and in practice archaeologists consider and test that hypothesis the same way they consider and test every other hypothesis. Rule this out by fiat and we have to accept Piltdown Man, or at least claim that the people arguing against the veracity of Piltdown Man were doing something other than Science.

A third bad response: "Satan is supernatural and science is not allowed to consider supernatural explanations." Fine then, replace Satan with an alien. I think this is a stupid distinction – if demons really did interfere in earthly affairs, then we could investigate their actions using the same methods we use to investigate every other process. But this would take a long time to argue well, so for now let's just stick with the alien.

A fourth bad response: "There is no empirical test that distinguishes the Satan hypothesis from the paleontology hypothesis, therefore the Satan hypothesis is inherently unfalsifiable and therefore pseudoscientific." But this can't be right. After all, there's no empirical test that distinguishes the paleontology hypothesis from the Satan hypothesis! If we call one of them pseudoscience based on their inseparability, we have to call the other one pseudoscience too!

A naive Popperian (which maybe nobody really is) would have to stop here, and say that we predict dinosaur fossils will have such-and-such characteristics, but that questions like that process that drives this pattern – a long-dead ecosystem of actual dinosaurs, or the Devil planting dinosaur bones to deceive us – is a mystical question beyond the ability of Science to even conceivably solve.

I think the correct response is to say that both theories explain the data, and one cannot empirically test which theory is true, but the paleontology theory is more elegant (I am tempted to say "simpler", but that might imply I have a rigorous mathematical definition of the form of simplicity involved, which I don't). It requires fewer other weird things to be true. It involves fewer other hidden variables. It transforms our worldview less. It gets a cleaner shave with Occam's Razor. This elegance is so important to us that it explains our vast preference for the first theory over the second.

A long tradition of philosophers of science have already written eloquently about this, summed up by Sean Carroll here:

What makes an explanation "the best." Thomas Kuhn ,after his influential book The Structure of Scientific Revolutions led many people to think of him as a relativist when it came to scientific claims, attempted to correct this misimpression by offering a list of criteria that scientists use in practice to judge one theory better than another one: accuracy, consistency, broad scope, simplicity, and fruitfulness. "Accuracy" (fitting the data) is one of these criteria, but by no means the sole one. Any working scientist can think of cases where each of these concepts has been invoked in favor of one theory or another. But there is no unambiguous algorithm according to which we can feed in these criteria, a list of theories, and a set of data, and expect the best theory to pop out. The way in which we judge scientific theories is inescapably reflective, messy, and human. That's the reality of how science is actually done; it's a matter of judgment, not of drawing bright lines between truth and falsity or science and non-science. Fortunately, in typical cases the accumulation of evidence eventually leaves only one viable theory in the eyes of most reasonable observers.

The dinosaur hypothesis and the Satan hypothesis both fit the data, but the dinosaur hypothesis wins hands-down on simplicity. As Carroll predicts, most reasonable observers are able to converge on the same solution here, despite the philosophical complexity.