« One more hurdle, cleared. | Main | Look around you, maths & germs »

July 26, 2006

Models, errors and the methods of science.

A recent posting on the arxiv prompts me to write down some recent musings about the differences between science and non-science.

On the Nature of Science by B.K. Jennings

A 21st century view of the nature of science is presented. It attempts to show how a consistent description of science and scientific progress can be given. Science advances through a sequence of models with progressively greater predictive power. The philosophical and metaphysical implications of the models change in unpredictable ways as the predictive power increases. The view of science arrived at is one based on instrumentalism. Philosophical realism can only be recovered by a subtle use of Occam's razor. Error control is seen to be essential to scientific progress. The nature of the difference between science and religion is explored.

Which can be summarized even more succinctly by George Box, famously saying "all models are wrong but some models are useful" with the addendum that this recognition is what makes science different from religion (or other non-scientific endeavors), and that the sorting out the useful from the useless is what drives science forward.

In addition to being a relatively succinct introduction to the basic terrain of modern philosophy of science, Jennings also describes two common critiques of science. The first is the God of the Gaps idea: basically, science explains how nature works and everything left unexplained is the domain of God. Obviously, the problem is that those gaps have a pesky tendency to disappear over time, taking that bit of God with them. For Jennings, this idea is just a special case of the more general "Proof by Lack of Imagination" critique, which is summarized as "I cannot imagine how this can happen naturally, therefore it does not, or God must have done it." As with the God of the Gaps idea, more imaginative people tend to come along (or have come along before) who can imagine how it could happen naturally (e.g., continental drift). Among physicists who like this idea, things like the precise value of fundamental constants are grist for the mill, but can we really presume that we'll never be able to explain them naturally?

Evolution is, as usual, one of the best examples of this kind of attack. For instance, almost all of the arguments currently put forth by creationists are just a rehashing of arguments made in the mid-to-late 1800s by religious scientists and officials. Indeed, Darwin's biggest critic was the politically powerful naturalist Sir Richard Owen, who objected to evolution because he preferred the idea that God used archetypical forms to derive species. The proof, of course, was in the overwhelming weight of evidence in favor of evolution, and, in the end, with Darwin being much more clever than Owen.

Being the bread and butter of science, this may seem quite droll. But I think non-scientists have a strong degree of cognitive dissonance when faced with such evidential claims. That is, what distinguishes scientists from non is our conviction that knowledge about the nature of the world is purely evidential, produced only by careful observations, models and the control of our errors. For the non-scientist, this works well enough for the knowledge required to see to the basics of life (eating, moving, etc.), but conflicts with (and often loses out to) the knowledge given to us by social authorities. In the West before Galileo, the authorities were the Church or Aristotle - today, Aristotle has been replaced by talk radio, television and cranks pretending to be scientists. I suspect that it's this conflicting relationship with knowledge that might explain several problems with the lay public's relationship with science. Let me connect this with my current reading material, to make the point more clear.

Deborah Mayo's excellent (and I fear vastly under-read) Error and the Growth of Experimental Knowledge, is a dense and extremely thorough exposition of a modern philosophy of science, based on the evidential model I described above. As she reinterprets Kuhn's analysis of Popper, she implicitly points to an explanation for why science so often classes with non-science, and why these clashes often leave scientists shaking their heads in confusion. Quoting Kuhn discussing why astrology is not a science, she says

The practitioners of astrology, Kuhn notes, "like practitioners of philosophy and some social sciences [AC: I argue also many humanities]... belonged to a variety of different schools ... [between which] the debates ordinarily revolved about the implausibility of the particular theory employed by one or another school. Failures of individual predictions played very little role." Practitioners were happy to criticize the basic commitments of competing astrological schools, Kuhn tells us; rival schools were constantly having their basic presuppositions challenged. What they lacked was that very special kind of criticism that allows genuine learning - the kind where a failed prediction can be pinned on a specific hypothesis. Their criticism was not constructive: a failure did not genuinely indicate a specific improvement, adjustment or falsification.

That is, criticism that does not focus on the evidential basis of theories is what non-sciences engage in. In Kuhn's language, this is called "critical discourse" and is what distinguishes non-science from science. In a sense, critical discourse is a form of logical jousting, in which you can only disparage the assumptions of your opponent (thus undercutting their entire theory) while championing your own. Marshaling anecdotal evidence in support of your assumptions is to pseudo-science, I think, what stereotyping is to racism.

Since critical discourse is the norm outside of science, is it any wonder that when non-scientists, attempting to resolve the cognitive dissonance between authoritative knowledge and evidential knowledge, resort to the only form of criticism they understand? This leads me to be extremely depressed about the current state of science education in this country, and about the possibility of politicians ever learning from their mistakes.

posted July 26, 2006 11:26 PM in Scientifically Speaking | permalink


The end of Jennings angered me.
He uses Occam's razor to choose the Copenhagen interpretation over many-worlds, which is just backwards. His dismissal of the anthropic principle as equivalent to itemized assumptions of "god made it so" is breath-taking.

I was suspicious of his discussion of objective reality, but my new rule of thumb is that his support is a strike against a philosophy.

Posted by: Douglas Knight at August 5, 2006 08:46 PM