> http://www.newscientist.com/channel/opinion/mg19826551.700-do-we-need...
>
> Do we need to change the definition of science?
> 07 May 2008
> From New Scientist Print Edition. Subscribe and get 4 free issues.
> Robert Matthews
>
> WHAT is the difference between astronomy and astrology? That's easy: astronomy is the scientific study of celestial objects, while
> astrology is a load of hokum. Anyone with the most basic understanding of science knows why. Astronomy passes the acid test of real
> science: its claims are always capable of being debunked - in other words, they are falsifiable.
>
> Identified as the defining characteristic of real science by the philosopher Karl Popper more than 70 years ago, falsifiability has
> long been regarded by many scientists as a trusty weapon for seeing off the menace of pseudoscience.
>
> The late Viennese thinker has been lauded as the greatest philosopher of science by the likes of Nobel prizewinning physicist Steven
> Weinberg, while Popper's celebrated book The Logic of Scientific Discovery was described by cosmologist Frank Tipler as "the most
> important book of its century".
>
> Times change, though. Popper's definition of science is being sorely tested by the emergence of supposedly scientific ideas which
> seem to fail it. From attempts to understand the fundamental nature of space-time to theories purporting to describe events before
> the big bang, the frontiers of science are sprouting a host of ideas that are seemingly impossible to falsify.
>
> “The frontiers of science are sprouting a host of ideas seemingly impossible to falsify”So should the pursuit of such mind-boggling
> ideas be condemned as pseudoscience, or should scientists be more relaxed about falsifiability? It's a debate that's dividing the
> scientific community. Some are in no doubt about where they stand. "I never would have believed that serious scientists would
> consider making the kinds of pseudoscientific claims now being made," says theorist Peter Woit of Columbia University, New York,
> author of Not Even Wrong, a biting critique of current fashions in theoretical physics. For Woit, attempts to water down the
> falsifiability criterion are "an outrageous way of refusing to admit failure".
>
> “The multiverse is no more pseudoscientific than the inside of a black hole”His bête noire is the recent explosion of interest in
> the multiverse, an infinite yet unobservable ensemble of universes of which our cosmos is supposedly just one part. "The basic
> problem with the multiverse is not only that it makes no falsifiable predictions, but that all proposals for extracting predictions
> from it involve massive amounts of wishful thinking," Woit says.
>
> Others believe such criticism is based on a misunderstanding. "Some people say that the multiverse concept isn't falsifiable because
> it's unobservable - but that's a fallacy," says cosmologist Max Tegmark of the Massachusetts Institute of Technology. He argues that
> the multiverse is a natural consequence of such eminently falsifiable theories as quantum theory and general relativity. As such,
> the multiverse theory stands or fails according to how well these other theories stand up to observational tests.
>
> In the meantime, says Tegmark, exploring the idea of the multiverse is no more pseudoscientific than pondering phenomena inside a
> black hole - another consequence of general relativity whose interior is just as unobservable as the multiverse.
>
> In any case, dismissing a theory on the grounds that it fails Popper's acid test itself involves a huge leap of faith, says
> cosmologist Lawrence Krauss at Case Western Reserve University in Cleveland, Ohio. "You just can't tell if a theory really is
> unfalsifiable."
>
> He cites the case of an esoteric consequence of general relativity known as the Einstein ring effect. In a paper published in 1936,
> Einstein showed that the light from a distant star can be distorted by the gravitational field of an intervening star, producing a
> bright ring of light around it. It was a spectacular prediction but also, Einstein said, one that astronomers stood "no hope of
> observing", as the ring would be too small to observe.
>
> For all his genius, Einstein had reckoned without the ingenuity of astronomers, which in 1998 led to the discovery of the first
> example of a perfect Einstein ring - created not by a star, but by a vast galaxy billions of light years away.
>
> Krauss admits he has fallen into the same trap, applying the falsifiability criterion to decide whether some or other idea is really
> "scientific" enough to be worth publishing. "I've decided not to write papers because I thought the claims would never be
> falsifiable, and yet [they] turned out to be so."
>
> Still, for many scientists, Popper remains the only philosopher with any relevance to what they do. Much of his appeal rests on the
> clear-cut logic that seems to underpin the concept of falsifiability. Popper illustrated this through the now-celebrated parable of
> the black swan.
>
> Suppose a theory proposes that all swans are white. The obvious way to prove the theory is to check that every swan really is white
> - but there's a problem. No matter how many white swans you find, you can never be sure there isn't a black swan lurking somewhere.
> So you can never prove the theory is true. In contrast, finding one solitary black swan guarantees that the theory is false. This is
> the unique power of falsification: the ability to disprove a universal statement with just a single example - an ability, Popper
> pointed out, that flows directly from the theorems of deductive logic.
>
> Popper went on to promote falsification as the essence of the scientific process, with the search for falsifiable predictions being
> the distinguishing feature between science and pseudoscience. Yet even at the time there were concerns his criterion wasn't up to
> the job.
>
> The most obvious objection is that astrologers, soothsayers and quacks also make falsifiable statements - but that doesn't make them
> scientific. Yet could it be their cavalier attitude towards negative evidence that marks them out as pseudoscientific?
>
> Worryingly, this doesn't work either, as was made clear over a century ago by the French philosopher and physicist Pierre Duhem. He
> pointed out that the predictions of a scientific theory often rest on a raft of other assumptions underpinning how the theory is
> tested. If an experiment seems to falsify the theory, it is often possible to pin the blame on one of these "auxiliary hypotheses"
> rather than the theory itself.
>
> This happens quite a lot in science. In fact, in the very year Duhem put forward his objections to falsification, experiments by a
> German physicist appeared to falsify Einstein's then-new special theory of relativity, lending support to rival theories. Yet
> Einstein blithely dismissed the results, saying the other theories were simply less plausible than his own.
>
> He was hardly the last scientist to reject inconvenient results - as Popper was forced to admit. Even so, he remained convinced that
> at least looking for falsifiable consequences was the essence of doing science.
>
> For Woit, it's precisely the absence of progress in finding such consequences of the multiverse theory that makes it pseudoscience.
> "If all you have to show is wishful thinking about the possibility of such progress, then you're not really doing science," he says.
>
> Yet according to philosopher Rebecca Goldstein of Harvard University, this just highlights the idealistic view of scientists
> underpinning Popper's criterion: "Not only does Popper maintain that science as a field is unique, its borders fortified by
> falsifiability, but also that the scientist is unique, detached enough from his own theories that he is only out to shoot them
> down." She says that in reality the process is far more positive - trying to find theories that work, rather than falsifying
> alternatives.
>
> Even when scientists accept that a theory has failed some test, they rarely junk it as being false. Popper recognised this too.
> Krauss points to the classic case of Newton versus Einstein. During the 20th century, Newton's theory of gravity was repeatedly
> "falsified" by observations: for example, by predicting only half the observed bending of light by the sun's gravitational field.
> Yet scientists are not about to ditch Newton any time soon, as his laws work perfectly well in everyday situations. "This is
> something we don't make clear enough," says Krauss. "We don't have true theories; we only have effective theories."
>
> So after all these concessions, what remains of Popper's supposedly hard-and-fast criterion? It's hard to apply in practice, too
> vague to differentiate science from pseudoscience and bears little resemblance to what scientists really do. Why does it remain so
> popular? "Scientists like simple methodological theories which accord well with what they consider to be good scientific reasoning,"
> says philosopher Colin Howson of the London School of Economics in the UK.
>
> So if the simplicity of falsification is misleading, what should scientists be doing instead? Howson believes it is time to ditch
> Popper's notion of capturing the scientific process using deductive logic. Instead, the focus should be on reflecting what
> scientists actually do: gathering the weight of evidence for rival theories and assessing their relative plausibility.
>
> Howson is a leading advocate for an alternative view of science based not on simplistic true/false logic, but on the far more subtle
> concept of degrees of belief. At its heart is a fundamental connection between the subjective concept of belief and the cold, hard
> mathematics of probability.
>
> Talk of probabilities usually conjures up images of random events such as coin tosses, with the formulae of probability theory
> answering questions about the chances of getting, say, 20 heads from 30 tosses. That's not the only way to look at probability
> theory, though. It is also possible to turn it on its head and ask a far more interesting question: what are the chances that a coin
> really is dodgy, given we've seen 20 heads from 30 tosses? In other words, if we have a hypothesis - like the belief that a coin is
> dodgy - probability theory allows us to assess that hypothesis in the light of our observations.
>
> This should sound familiar; after all, it is what scientists do for a living. And it is a view of scientific reasoning with a solid
> theoretical basis. At its core is a mathematical theorem, which states that any rational belief system obeys the laws of probability
> - in particular, the laws devised by Thomas Bayes, the 18th-century English mathematician who pioneered the idea of turning
> probability theory on its head.
>
> Unlike Popper's concept of science, the Bayesian view doesn't collapse the instant it comes into contact with real life. It relies
> on the notion of accumulating positive evidence for a theory which, according to Tegmark, is what scientists really spend their time
> doing. "What we do in science isn't falsifying, but 'truthifying' - building up the weight of evidence," he says.
>
> The Bayesian approach quantifies this practice. Scientists begin with a range of rival explanations about some phenomenon, the
> observations come in, and then the mathematics of Bayesian inference is used to calculate the weight of evidence gained or lost by
> each rival theory (New Scientist, 22 November 1997, p36). Put simply, it does this by comparing the probability of getting the
> observed results on the basis of each of the rival theories. The theory giving the highest probability is then deemed to have gained
> most weight of evidence from the data.
>
> It captures many other features of real-life science too. For example, it shows that seemingly implausible theories require a hefty
> weight of evidence before they can be taken seriously - reflecting that familiar maxim that "extraordinary claims require
> extraordinary evidence". The Bayesian view also gives vague or contrived theories that fit pretty much any data set a tough time in
> the quest for credibility.
>
> With its mathematical rigour and natural fit with real-life science, it's an approach that now commands the attention of many
> philosophers of science. "The most interesting views these days are to be found in Bayesianism. It's where much of the current
> research impetus is directed," says philosopher Robert Nola of the University of Auckland in New Zealand. He adds, though, that the
> approach is not without its problems.
>
> Chief among them is that, while Bayesian methods show how observations add weight of evidence to initial beliefs or theories, they
> say nothing about what those initial beliefs should be. And if a theory is completely new, the beliefs behind it may be based on
> nothing but subjective intuition.
>
> Advocates of the Bayesian approach point out that such prior beliefs typically become less important as the results accumulate. In
> other words, Bayesianism confirms another maxim of scientists: that as the observations come in, the truth will out. Wrong-headed
> initial beliefs are never totally falsified, but they do end up buried by the sheer weight of evidence against them.
>
> It is not just philosophers of science who see Bayesianism as the way forward: so do working scientists in fields from archaeology
> to zoology. Among the proponents of this view are cosmologists, who are now using Bayesian methods to extract the most plausible
> model of the universe from signals flooding in from observatories. One of their prime roles is constraining speculation and deciding
> whether current theories are compatible with observations, or if some extra ingredient is needed.
>
> Take the mysterious force said to be driving the ever-faster expansion of the universe. Theorists are exploring the idea that this
> "dark energy" may have varied over the course of cosmic history, rather than stayed constant. Such ideas might keep theorists in
> work but they also make for a more complex model of the universe, says Andrew Liddle at the UK's University of Sussex in Brighton.
> "The question is whether the observational data support a simple or a complex model."
>
> He and his colleagues have applied Bayesian methods to assess the plausibility of the intriguing idea of varying dark energy and
> found that the standard model with constant dark energy remains a far better bet. That could change, but the smart money is on
> variable dark energy being a dead end (New Scientist, 8 March, p 32).
>
> Talk about "best bets" and "smart money" might not sound very scientific, but it's much closer to how real-life research priorities
> are decided. With Bayesian methods, that process is captured in rigorous, quantitative detail - the black and white of falsification
> being replaced with the shades of grey of the real world. "I think it's absolutely the way to go," says Liddle.
>
> So where does all this leave the debate about whether concepts like the multiverse are really scientific? According to Howson, the
> multiverse is entirely scientific in Bayesian terms, as it is based on theories carrying huge weights of evidence. "If Popper
> condemns it as pseudoscience because it is 'unfalsifiable' - and it may not always be - then so much the worse for Popper."
>
> But whatever one regards as the essence of science - black-and-white falsification or subtle shades of grey - in the end it is still
> empirical observations that decide if a theory gets taken seriously. "At some level, you cannot give up the idea of falsification,"
> says Krauss. "Rumours of the death of science have been greatly exaggerated."
>
> Robert Matthews is visiting reader in science at Aston University, Birmingham, UK
> From issue 2655 of New Scientist magazine, 07 May 2008, page 44-47