Falsification - right or wrong?

The correct methodology for science, according to Karl Popper.

The process of science, according to Professor Sir Karl Popper, was to conjecture, to hypothesise, and then attempt to falsify that hypothesis. You needed to set up an experiment to try to prove your hypothesis wrong. If it was disproved, you had to reject it. Simple.

Popper came to this conclusion at a time when the general view was that the scientific method was all about verification. Whilst verification intuitively sounds like the best way to go, it really isn’t. As Popper saw with Freudian and Adlerian psychoanalysis, Marxism and astrology, a wish to provide verification generally meant that people looked only for evidence to support their view of things, rather than looking for inconsistencies.

Now you might think that verification and falsification are two sides of the same coin, but they’re not. In fact verification, in philosophical terms, was an example of trying to impose standard philosophical methods on science without really understanding the role of science. Verification is fine if you have a logical puzzle: you can check for errors in logical reasoning because it follows pre-defined rules. If there are no flaws, then the proof is accepted. It is verified.

Unfortunately, the real world, the world about which science is trying to inform us, doesn’t work like that. It’s very different because we don’t start off knowing what the rules are. We start instead from a set of observations of what is going on and then try to infer from our observations the underlying rules which govern what is happening. If logic alone had been sufficient to give us the structure of the atom and otherwise sort out all the problems of science, then the ancient Greeks would have had mobile phones and been talking about the Big Bang rather Zeus and his bolts of lightning.

Instead, we have been on a voyage of discovery over very, very many millennia in trying to understand the rules governing what happens under what circumstances. Thanks to the thinkers of the Renaissance, we did eventually decide not simply to adopt those rules which were thought to fulfil a requirement for ‘beauty’, or for consistency with how the ancient Greeks believed things worked, or for their supposed alignment with religious teaching.

We took speculations – hypotheses – and conducted experiments to see whether the hypotheses, those assumed rules, really did explain our physical reality. And very often they didn’t. A theory might, even for many centuries, seem to have been ‘verified’ by a whole raft of experiments, but nature has a way of coming up with exceptions to the rule. The most famous case of falsification is the discovery that Newton’s ‘Laws’ of Motion do not actually apply at velocities close to the speed of light. Thank you Einstein. Which takes us back to Popper and the counter-intuitive need for falsification.

So then, if we have a theory which cannot be tested and so cannot ever be shown to be false, Popper takes the view that it is not even worthy to be called a scientific theory. It may be a metaphysical speculation, but it is not science. Popper though was speaking at a time when certain very problematic scientific ideas had not yet come into peoples’ heads. I’m thinking here of things like multiverses, string theory, dark matter and energy and so on. These are so far beyond our ability to conduct experiments that they are not in practice falsifiable. They are though probably in principle capable of being falsified, unlike, say, the alleged existence of invisible fairies at the bottom of my garden. It is just that they are on a scale such that we do not have the physical means at the moment to do the research. But then much of our present day experimenting would not have been possible even 20 years ago. Think of the Higgs particle.

So then, whether we call these (currently) untestable hypotheses scientific theories or metaphysical speculation is not really of great importance. Either way, they will have to remain on the back-burner for the time-being.

And then Popper also held it to be very important that we should not try to change a theory by putting in extra variables retrospectively to make the experimental data fit the hypothesis. In this, said Popper, lies the great distinction between science and pseudoscience: the latter will try to protect itself from disproof by ‘massaging’ its theory in the light of conflicting facts. He could see the obvious truth that pseudoscience, such as astrology, has a certain ‘plasticity’ which enables it to be adjusted to fit whatever inconvenient facts are thrown at it. But in real science, Popper said, you can’t adjust the hypothesis to fit the data

And of course, it is true even today that pseudoscience typically surrounds itself with acolytes who for extraneous reasons do not want to look for actual evidence that it may be wrong. If it looks in danger, they will always suggest some random factor which might explain the discrepancy. Hence the anti-vax movement which, every time one of their silly ideas is shown to be wrong, will come up with another equally incoherent idea as to why the vaccine is dangerous or the virus is a hoax.

But leaving aside this sort of nonsense, in the form at least initially put forward by Popper, his great theory has always been susceptible to criticism, in fact, some would say to being falsified. Philosophers have argued that:

1.    when an experiment fails to be consistent with a hypothesis, it must always be possible that an element of the experimental set-up itself could be to blame, rather than the hypothesis. So then they say that we can never be sure that the apparent falsification is real;

2.    neither is it right to suggest that the hypothesis should never be tweaked after the results come in. The results may genuinely suggest an additional factor of relevance which, when taken into account, prevents the resulting modified hypothesis from being false;

3.    we have to be very cautious about upending well-established laws of physics – rather, they would say, our experiment should prima facie be regarded as faulty.

All of which is true – up to a point. It’s just that these philosophers, whilst arguing over the finer points of theory ignore the way in which scientists actually do their work: scientists take falsification as a basis and then pragmatically adapt it to the real world.

Their answer to the philosophers’ theorising is that, obviously, great care has to be taken in establishing the conditions of the experiment. If not, then the result is hardly worth having. It is also good practice not to rely on doing the experiment only once. Most scientists would do the same experiment over and over again precisely in order to try to eliminate error in the experimental set-up.

This is also why if an experiment produces an apparent denial of our fundamental understanding of how things work then, rather than immediately accepting the need for a revolution in our thinking, other scientists will attempt to replicate the experiment in their own labs in order to make sure that there wasn’t an error in the way the experiment was conducted.  Others will dream up other ways of testing the hypothesis. A good example of the reaction of the scientific community was what happened when the startling claim was made by Pons and Fleischmann that they had achieved nuclear fusion at room temperature – cold fusion.

Ultimately, however, if no error can be shown in the experimental methodology, then the inconsistency of the hypothesis with the experimental results will act as a very large nail in its coffin. It cannot perhaps be said to have been falsified beyond all shadow of a doubt, because it might, after all, just have been experimental error. As far as the scientific community is concerned, however, it will have been falsified beyond reasonable doubt. A pragmatic position to take, if not as clear cut as the philosophers - Popper included - would like. Scientists have to live with doubt, knowing that all of science is tentative. Philosophers seem always to insist on certainty, even where there can be none.

In contrast to the philosophical world, however, some industries and interest groups have very deliberately taken Popper’s philosophy to heart - and not in a good way. For decades, the tobacco industry said that the theory that tobacco smoke caused lung cancer could not, of course, be verified, but neither was it capable of being falsified. There simply wasn’t the data, because no randomised controlled double-blind trials had been or could be done in order to see whether smokers died earlier than non-smokers. But the mass of epidemiological data showed that there was a clear correlation between smoking and cancer. Their reply was that correlation does not mean causation. Again, quite correct, but surely on any version of ‘better safe than sorry’, the EU’s precautionary principle, it would have been better to at least heavily discourage smoking a lot earlier than we did.

We have seen and still see a similar line of reasoning with climate change. Here, vested interests are attacking the science, saying that there is and can be no conclusive evidence that the climate will change in the way the scientific consensus predicts. And they are saying that the modelling cannot currently be falsified because its predictions are about a future world. Then they say that the disaster scenario produced by the modelling has changed over the years and so might change again in a different, more benign, direction. In the meantime, of course data consistent with the modellers’ predictions is coming in thick and fast.

I would not claim that Popper’s idea of falsification is as simple or clear-cut in its application as Popper himself clearly thought at the outset. We do not often have a nice neat theory easily capable of being shown to be wrong. I would though argue that Popper’s insight, in turning away from verification to falsification, has given us a major benefit in the way that scientists now do their work and the protocols they apply to it. What we might call ‘pragmatic falsification’ is their tool of choice and it’s one that has been shown to work very well.

See also: Conjectures and Refutations

Paul Buckingham

2 August 2021

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