Friday, 21 April 2006

The Nature of Scientific Theories

Two controversies are bubbling along at the moment which made me think about what science claims. The Evolution vs. Intelligent Design debate seems to be hotting up again, and there is controversy about climate change. Now I should immediately state that I think that Evolution is the best guess we have about how organisms developed, and that man-made factors are responsible for significant climate change that could, eventually, prove to be catastrophic. Those beliefs are supported by evidence, but that evidence is not incontrovertible.

It may be, for instance, that the Theory of Evolution will be modified and improved again. Certainly since Darwin we have seen some intriguing new ideas, such as
punctuated equilibria. So we claim too much if we say Evolution is correct. The best theory we have at the moment consistent with the evidence is more like it.

Things are even more troubling in the area of climate change. There we have rather little experimental evidence (building new planets to test climate change theories being somewhat impractical). So we just have direct measurements of the Earth's climate, and (almost certainly correct) inferences based on things like differential oxygen isotope measurements. In addition, there are computer models of the climate, but these suffer from potential model error: they are build to calibrate correctly to known physics and known measurements, but there is enough uncertainty that their predictions about future climate may not hold, and moreover that uncertainty is difficult to quantify. That said, the overwhelming evidence both paleoclimatological and more recent is that there will be significant further global warming with catastrophic effects on mankind. But it is not certain in the same way that a prediction of Newtonian mechanics is.

In this mix, of course, we need to add significant vested interests, such as the deeply irresponsible Exxon-sponsored climate change denial, and the influence of the religious right on the abortion debate. But the best counter to this is not to overstate the claims of science. Politicians may not wish to hear carefully stated, potentially uncertain results but scientists do them, and us, a disservice if they claim a higher epistemological status than they deserve.

Finally, although scientists may wish to believe that their practice is objective, we cannot dismiss cultural factors. Kuhn's changes of paradigm are usually accompanied by significant resistance from the scientific establishment because the figures in power have cultural capital invested in the old view. The lone scientific hero who defies the establishment to champion a correct theory is a horny old stereotype, but we should also not forget that there are many such figures who happened to be wrong. It is only eventually that we figure out who had the better guess.

Irritating and almost certainly wrong though the proponents of intelligent design and the climate change deniers are, therefore, we cannot say their ideas are absolutely incorrect. Non-scientific, politically and/or religious motivated, and unlikely to be true, certainly. Not the best guess given the evidence, undoubtedly. But not certainly wrong.


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