Monday, November 14, 2011

Is it science?

One of the things I like to ponder is how to decide whether something is science or not.  An attempt to come up with a clear demarcation criterion is Karl Popper's, which gets more widely distributed as being "If it isn't falsifiable, it isn't science."   I'm not sure what he said himself, but philosophers tend to write books on these topics, rather than short sentences, so I'll guess that some details are lost in this version.

The question arises here because a recent question at the question place (yes, Robert, that's exactly what it's for) mentioned Popper.  I'll give a different response and discussion here.  (Same conclusion*).

For some cases, Popper's falsifiability criterion works well.  Religion is not science.  There is no observation, experiment, or test that will tell someone that their religion is wrong.  No matter what you observe, the religion can accommodate it.  Same thing for mathematics, actually, as it isn't necessarily concerned with observations.  Unfortunately, those (theology and mathematics) are the only two areas which can lay claim to absolute Truth (of a sort -- mathematical truth is only about mathematical things).  Science is left with only approximate truth -- the theory seems to work pretty well, the observations are pretty reliable.  But not absolutely reliable, and not absolutely perfectly.

For others, though, it's more difficult.  In the later 1800s, astronomers observed that the planet Mercury wasn't where it was supposed to be according to Newton's laws.  Its point of closest approach to the sun (perihelion) was moving by 43 seconds of arc per century too much$.  If Popper's criterion were correct, astronomers and physicists should have immediately thrown out Newton's laws and gone looking for something else.  Instead, some patches were suggested -- like a planet 'Vulcan', orbiting even closer to the Sun than Mercury, in just such a way to cause Mercury to behave as observed.  But it was never observed.  Eventually, Einstein proposed his theories of relativity to expand on Newton's laws.  Among other things, they explained why Mercury wasn't where Newton expected it to be.

For climatology, Popper is not so much relevant, or at least doesn't pose very much difficulty.

Popper's criterion is mostly concerned with theories, not observations.  And climatology has few theories of its own.  It borrows theories from other areas of science -- the laws of conservation of mass, energy (first law of thermodynamics), and momentum (Newton's laws), the second law of thermodynamics, Planck's law for blackbody radiation, quantum mechanics (to get emission and absorption of radiation by gases), and a few more subtle matters.  Climatology also makes some use of observations -- where are the absorption lines of CO2 and how strong are they, what is the saturation vapor pressure of H2O, what is the freezing point of water, and so on.

To the extent that people complain about climatology, and climate models, the theory (theories) that have to be wrong are from somewhere else (usually physics).  The climate models are just trying to carry out the laws and theories from physics.

Popper's criterion, to come back to it, doesn't have much to say about observations.  I am 6'1" (185 cm) tall.  At least I claim that this is true.  Suppose you come to my house and measure my height and see that I'm, instead, 184 cm tall.  Maybe you've 'falsified' my claim.  But what has changed in the world of science?  Nothing.  No portion of science relied on me being 185 cm tall rather than 184 cm tall.  Certainly far less depended on that than depended on Mercury's orbit, and that didn't, on its own, cause the downfall of Newton's mechanics and gravity.

But the law(?), theory of conservation of energy is something to falsify.  It _could_ be falsified.  If you observed the amount of energy in a system at one time, and then some time later saw that it had less (or more), you'd be on your way to a Nobel prize.  Or at least a new revolution in science.  One of the major importances of Einstein's E = mc^2 was that it showed there was a new place to find energy in the universe.  Odds are good, given the 100+ years that people have been at it, that you've just made an error in your observation process.  Still ... maybe you've got something.

Rather than drive on to a firmer conclusion, I'll stop here and invite discussion.  What theory or theories do you think climatology has that couldn't be falsified?  Which ones do you think have already been falsified?  If you think climatology is making claims which could not, even in principle, be falsified, what are they?  Is Popper's criterion even a good one to use?  And so on. 


* There's an old story that goes:   A student who was not doing very well in a class discovered that their professor always gave the same test every year.  Even better, it was multiple choice.  So they tracked down an old, corrected, copy of the test and memorized the answers.  Come the day of the final, they checked off all the previously-memorized answers.  Then was extremely surprised to have gotten an F (failing grade).  After some internal debate, the student went to the professor and said what they had done.  The professor answered "Yes, I give the same questions every year.  But I change which answers are correct!"

$ 43 seconds of arc is a seriously small number.  A circle has 360 degrees.  Each degree has 60 minutes of arc.  Each minute of arc has 60 seconds of arc.  The difference was 43 / (360*60*60) of a circle -- 0.00003318 of a circle (about 33 parts per million, far less than the fraction of the atmosphere that is CO2, and small enough that the thickness of the line when you draw a circle is much larger than this).

15 comments:

Tom Curtis said...

I recommend you look up the work of Imre Lakatos, who provides a much better basis for understanding the operation of science than does Popper.

Anonymous said...

"And climatology has few theories of its own. "

I would disagree. The theories of climatology are certainly based on the theories of other fields, but they are combined to create new theories/hypotheses/etc.

For example: increasing GHGs will warm the surface and cool the stratosphere. That one is well grounded and won't be overturned, but we could imagine a slightly different theory where GHGs lead to warming of the whole column (because we forgot to take into account stratospheric ozone absorption). Lindzen's "Iris" would have been a climatological theory if it had held up. Currently, instead, we theorize that there is a positive feedback from cloud response to GHG-induced warming, but there's still work to be done there...

Or do you have a different definition of theory which only applies to "fundamental" concepts like Newton's Laws, Relativity, Maxwell's equations, etc? I acknowledge nomenclature in this area can be fuzzy...

(I do agree that I find Popper to be... less than useful, especially when cited be people who's only goal is to be contrary)

-MMM

Word verification: "messey"!

Robert Grumbine said...

From Richard Harter: I will commend to you my review of Imre Lakatos's essays at http://home.tiac.net/~cri/1999/lakatos.html. If nothing else it should give you a sense of the quagmire you are wading into.

Robert Grumbine said...

Tom:
Lakatos is not without his problems either. See Richard Harter's review (link from his comment).

MMM:
I think we are indeed differing in how we define 'theory'. I take it as something which explains many different observations and the results of many different (possible) experiments. Newton's theory of gravity and theories of mechanics explains the motions of stars, planets, apples, clouds, and tornadoes. Darwin's theory of evolution explains antibiotic resistent bacteria, the platypus, why humans have the same number of fingers as gorillas, why cats and dogs both have 4 limbs, and so forth.

Your example for climate is, I would say, a prediction: "Increasing greenhouse gases will warm the surface and cool the stratosphere." But that is a single item, not a broad tool for making further predictions. The theories which would be undermined by a contrary observation are conservation of energy, and quantum mechanics -- the theories climatologists used in making that prediction.

As your verification word has it, correctly, it's a messey area!

Richard:
Thanks for the link. I've now read the article, and it is helpful. One of these days I'll have to read Lakatos directly. But this is a nice intro.

Anonymous said...

Hi Bob,

Popper repays reading because he is a wonderfully clear writer and a very clear thinker. What most people know of him is the falsifiability criteria, which is - as you say - not much cop on its own and far from being the whole of his contribution to science.

Your example of planetary orbits is interesting because Popper writes about that extensievly. Without Newton's laws no one would have known that the planets were misbehaving, that's a scientific problem that spurs further investigation. (he was big on scientific problems)

Einstein's understanding of gravity explained Newton as a special case but in addition made a number of predictions that differed from Newton (as well as other etherous explanations)

When the observations agreed with Einstein and not Newton, Newton was effectievly falsified, but it didn't prove Einstein right. In fact you could make those same observations a trillion times and not prove Einstein any more right.

It's not until we have another theory - either because Einstein is failing to predict something or because the theory comes out of the blue skies of someones imagination - that we'll know what observations to make to decide who's right.

Popper talks a whole lot about observations (the above example and others) and their connection to hypotheses and theories. His favourite demonstration of the theory-laden nature of observations is to command his audience (or reader) "Observe!"

As a bald command it is absurd, all observation is guided by some theory or expectation. Or so argues Popper.

His more general approach was that of conjectures and refutations. One proposes new ideas, hypotheses, theories in hte knowledge that they may never be perfect. These are then refined over time by argument, discussion and observation.

An important ingredient of this is the necessity of writing things down. If an argument is in your head it is nebulous, subjective and susceptible to change. Once it is written down (although one can argue over the meaning of the words) it is objective. It forms a focus point for discussion, critique and further work. From there the importance of the peer reviewed literature is obvious.

Another thing he was keen on - an important part of the wider climate debate - is stating ideas as clearly as possible and finding grounds between two people that they can both agree is sufficient evidence to decide for (temporarily for) or against a theory. Without being able to decide on what those grounds are - which involves sometimes spooling all the way back to first principles - little advancement can be made in science, or a meaningful dialogue about science.

Nebuchadnezzar

Peter said...

If Popper's criterion were correct, astronomers and physicists should have immediately thrown out Newton's laws and gone looking for something else.

Er, no? The predictions for Mercury's movement relied on two things: Newton's laws, and the assumption that all the gravitationally-interacting bodes were already known.

When observation contradicted the prediction, that prediction was falsified, and something had to be thrown out. Sensibly, given that it would be perfectly reasonable to have missed seeing a small planet close to the Sun, they threw out the italicised assumption above. Subsequently, Einstein's improved theory allowed them instead to throw out Newton's theory and replace it with a more refined version.

Neither of the above lines of thought, however, violates the principle of falsifiability. It only appears to violate it if you neglect the unspoken initial assumption. But a theory can't make predictions without inputs!

Tom Curtis said...

Richard Harter's review of Lakatos is interesting, and raises several of the key issues in understanding Lakatos. I found that while I agreed with him on some points, on others I believe his criticism of Lakatos' theory to be incorrect. Of the major points, four bear mentioning:

1) Harter writes that Lakatos did not correctly understand Kuhn, but it is essential to Kuhn's theory that paradigm's be incommensurable. Given incommensurability, there is an essential a-rationality to paradigm shifts which Lakatos rightly rejects. Indeed, in an interesting dialogue between the two, Lakatos proposed, and Kuhn agreed that this was the essential difference between the two of them. Except for commensurability, the difference between Lakatos' "scientific research programs" and Kuhn's "paradigms" would be trivial. However, IMO, Kuhn's thesis of incommensurability fails as a description of science (although it may well be psychologically true of individual scientists).
http://plato.stanford.edu/entries/thomas-kuhn/#4

2) I believe Harter gives too short shrift to the idea of a progressive problem shift. For Lakatos a progressive problem shift is one in which the emperical content of a scientific research program increases. He is aware than many very successful research programs have included negative problem shifts, shifts which either do not alter, or reduce emperical content. For that reason he says that scientific research programs can always be ressurected.

Never-the-less, what distinguishes between successful and unsuccessful programs is the extent to which their problem shifts are progressive. What distinguishes pseudo-science is almost uniformly negative problem shifts. Most pseudosciences begin with a genuinely emperical hypothesis. It is not how whether they make any successful predictions that marks them as pseudoscience, but the trajectory they take in accounting for recalcitrant experience.

3) Harter claims that Lakatos only discusses examples from physics (which is true) and implies that the theory is only applicable to physics (which is false). Certainly, the concept of a scientific research program makes brilliant sense of the course of Darwinism (and of the decline of its rivals into pseudoscience). As Harter rightly observes, the world is messier than Lakatos allows but that messiness does not restrict the applicability of his theory.

4) Finally, Harter correctly describes Lakatos as doing a sociological analysis of how science works in practice. What Lakatos has also done is described a minimalist prescriptive program for successful science. Any scientist taking Lakatos' description of science as methodologically prescriptive will contribute to the advance of scientific knowledge. There may be better prescriptions available, that will enable scientists to work more efficiently. However, they are as yet unproven, and will in all probability be found to be refinements of rather than radical departures of Lakatos' methodology of scientific research programs.

Alastair said...

“When I use a word," Humpty Dumpty said in rather a scornful tone, "it means just what I choose it to mean - neither more nor less.”

The word I would like to use in that way is "axiom" with the meaning that it is a logical statement that is assumed to be true (http://en.wikipedia.org/wiki/Axiom). I other words I am using it to refer to not just self evident unproven truths but also to the scientific laws derived from those unproven truths. Thus a paradigm is the set of axioms on which a scientific program is based. A paradigm shift happens when one of these axioms is discovered to be false.

I tend to think of the tree of knowledge as having a trunk, branches and twigs. In normal science the twigs are sprouted, grow and the tree becomes larger. But if a branch becomes infected it has to be cut off and a new branch grown in its place. Replacing a branch is equivalent to Kuhnian revolutionary science.

IMHO, the Kuhnian Theory is itself a paradigm shift. That is why the Lakatos and the Kuhn theories are incommensurable. Lakatos believes, holds as an axiom, that once a scientific law has been accepted as true it will remain that way forever, much as in the way that this is true for mathematical theorems. Kuhn, does not hold that view, knowing that established beliefs (my "axioms") can be overthrown.

Of course Lakatos accepts the Copernican revolution but I suspect for him the epicycles were pseudo science. That is being wise after the event. We cannot know how much of present science is true. Einstein showed that with Newton's Laws. And we can be even less sure that new sciences such as climate science will not be revolutionised.

P.S. Thanks to Richard Harter for that review. I agreed with everything you wrote except perhaps that Kuhn like Lakatos made mistakes :-)

Cheers, Alastair.

Robert Grumbine said...

Some good ideas here. I'm sorry I won't be able to follow up for a while due to a family emergency. In the mean time, I'll suggest reading the philosophers mentioned directly. What Kuhn, Popper, Lakatos actually said seems often not to be close to what gets attributed to then. And, as we've seen already in the comments, there can be profound differences of opinion even between people who have read the originals.

Tom Curtis said...

Robert, sorry to hear about your family emergency. I hope it all works out fine.

Tom Curtis said...

Alistair,

Your axiom that Lakatos holds that scientific theories, once accepted, can never be refuted is a clear misreading of his thought.

Certainly he considered Newton's research program (as detailed in the Principia) to be a paradigm example of a successful scientific research program that has since been superseded both by General Relativity and by the development of Quantum Mechanics.

Anonymous said...

Speaking of the philosophy, history and sociology of science, this series of radio shows is very interesting:

http://www.cbc.ca/ideas/episodes/2009/01/02/how-to-think-about-science-part-1---24-listen/

Nebuchadnezzar

Alastair said...

Tom, you wrote:

"Your axiom that Lakatos holds that scientific theories, once accepted, can never be refuted is a clear misreading of his thought."

Yes, you are correct. I have got Lakatos wrong. In a broadcast, and a fuller transcript both available from this web page:
http://www2.lse.ac.uk/philosophy/about/lakatos/scienceAndPseudoscience.aspx
he says:
"What, then, is the hallmark of science? Do we have to capitulate and agree that a scientific revolution is just an irrational change in commitment, that it is a religious conversion? Tom Kuhn, a distinguished American philosopher of science, arrived at this conclusion after discovering the naivety of Popper's falsificationism. But if Kuhn is right, then there is no explicit demarcation between science and pseudoscience, no distinction between scientific progress and intellectual decay, there is no objective standard of honesty."

and later he says:
"Kuhn is wrong in thinking that scientific revolutions are sudden, irrational changes in vision."

I, of course, disagree with his last statement. I believe that a scientific revolution or Kuhnian paradigm shift is the result of a new axiom, which is a sudden and, in a way, an irrational change.

I now think that an axiom which separates Lakatos from Kuhn is Lakatos' belief that there is an "explicit demarcation between science and pseudoscience." I, and I suspect Kuhn, take a more Humean attitude, believing that we can never be certain of empirically derived laws.

The reason why Kuhn found that the supporters of the old and new paradigms had difficulty conversing is that often the changed axioms are implicit and not stated. Thus the two camps are arguing from different points of view.

On the other hand it may just be conservatism that prevents supporters of the old paradigm accepting the new. Max Plank wrote:
"A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it."

Cheers, Alastair.

David B. Benson said...

Karl Popper eventually gave up on the absolute nature of falsifiability. Thomas Kuhn eventually gave up on his nature of scientific revolutions, at least in part.

I prefer a Bayesian approach: that hypothesis is best which receives the most support from observations. If two receive (nearly) the same support then the simplier of the two is to be preferred. This inductive logic approach seems much closer to the way (careful) scietists actually approach their respctive subjects.

Hank Roberts said...

aside--the 'question place' link in your 2nd para. at main post seems broken