Monday, September 24, 2007

Kuhn, Popper, and Intelligent Design

Mike the Mad Biologist has a post regarding the references to Thomas Kuhn's notion of paradigm change in the intelligent design discussions. (I do hesitate linking to Mike from this humble little page now that he's getting links from the A-blogs, but perhaps he'll think it quaint.) Mike is exactly right about a couple of things:

Paradigm shifts are very rare. Anytime you hear about a 'novel' theory, remember this. Einstein had one. Darwin had one. Kimura had one. Not too many other have. This is a very good thing, since if fields fundamentally shifted every month, it would be very hard to get any work done (and this would be good evidence that the work itself was very shoddy).
Yes, the overwhelming number of working scientists do what Kuhn called "normal science," which is firmly embedded in the paradigm guiding science and revolutions are so rare that when they happen, it is truly momentous.

There's a difference between a perspective or worldview and a theory. Theories (and hypotheses) can be replaced by new data or analyses. Many so-called theories aren't rigorous theories that can be falsified (and I'm not getting into an argument about Popper). How do you falsify an intelligent designer?
For Kuhn, a paradigm brings with it an entire worldview. It contains foundational propositional beliefs; it defines what counts as the sort of questions that can be asked and which are worth pursuing; it defines what what approaches are deemed legitimate for answering questions; and it defines what counts as a meaningful answer. In this way, Kuhn appropriates an idea that goes back to Pierre Duhem, that a paradigm is not falsifiable because you can always make adjustments within the web to account for any anomalies that pop up. Some anomalies are easily swept under the rug and others require major, artificial ad hoc modifications, but you can save any part of the paradigm if you are willing to adjust somewhere else.

In this way, not only is Intelligent Design not falsifiable in Popper's sense, but neither is evolutionary theory, quantum theory, or anything else for that matter. The move to Popper, which is so frequently made, is a flawed one because hypotheses are not tested individually. They are parts of larger webs of belief and may be saved by twisting other parts of the web in order to account for seemingly problematic observations.

Does this then indicate some sort of epistemological equivalence between evolutionary theory and intelligent design? No. It just means that Popper is not the right figure to pull from. There are some smart folks working very hard to show that there may be testable consequences from intelligent design theory and it would be a mistake to maintain a priori that they must be wrong. Maybe it is testable in some indirect way, maybe not. The point is, that that does not really matter because falsificationism is not the place to look for the criterion of theory choice here.

Imre Lakatos was a student of Popper's who also found certain things about Kuhn's view deeply attractive. He realized the problems with the use of falsifiability of individual hypotheses as a criterion of demarcation for science that arose from Kuhn's insights. but he also saw one of the glaring problems with Kuhn's system. If a paradigm is a worldview and defines the questions, means of answering them, and what counts as acceptable answers, then all of rationality resides within the paradigm. As such, there can never be good reason to move from one paradigm to another as reasons only make sense within a paradigm.. There is no way to comparison shop for paradigms and so paradigm shift is akin to religious conversion.

Lakatos used Popper to solve this problem in Kuhn. Popper pointed out that falsified propositions could be saved by the use of ad hoc hypotheses and ruled them out as not allowable. For Kuhn, they are allowable. Lakatos' insight was to reformulate Kuhn so that while they are permitted, they are a liability to theory acceptance. And research programme (as he renamed paradigms) could be saved by tweaking some other part of the theory, but when your tweak limits the relative testability (making less falsifiable in a sense), it becomes "degenerate." When the research programme is able to explain more and more without ad hoc modifications, it is seen to be progressive. Kuhn is right (and Popper wrong) that you are never forced to rule out any theory, it can always be saved from problematic data and still be scientific. But Popper was right (and Kuhn wrong) that the ad hoc manner of saving it doesn't come with a rational price.

As such, when we look at Intelligent Design and Darwinian Evolution, we have two research programmes that can be maintained regardless of the data. But it happens that ID is quite degenerate requiring all kinds of patches that do not increase its independent testability to account for observable phenomena. Evolutionary theory, on the other hand, is an unbelievably progressive research programme that accounts for a staggering amount of data ranging from macro-ecological facts, to micro-level genetic facts to geological facts. Darwinian evolution is testable in so many, many ways and in the overwhelming number of them easily accounts for observations. Are there anomalies? Of course. Every theory has anomalies. Will some of them be resolved with the addition of facts now unknown. Sure. Will others force us to rethink parts of the theory as it is now accepted. No doubt. Are there some that will cause the entire research programme to become degenerate and make it less than rational to cling to? Possible, but I'm a better bet to win the Tour de France next year.