WMD

    Words of Mass Dissemination

The debates over creation science (and more specifically, intelligent design) and evolution continue to heat up, although reasoned discussion (indeed, successful communication) is still difficult to find. It is difficult to say anything about the issue without being abruptly labeled an insensitive supercilious atheist or an anti-intellectual blind ignoramus. I’ll try. Because I have little sympathy for the extremists on either side, however – and because non-extremists are apparently either rare or in hiding – I suspect that I will be labeled both. (Non-extremists do exist. Michael Ruse is, I think, arguably moving towards – perhaps already occupies – a helpful viewpoint that many would do well to study.)

One of the many battle-fronts that has opened up in this war concerns whether (neo-) Darwinian evolution is ‘just a theory’. Apparently, both parties to the debate feel that a great deal turns on this issue.

“Evolution is a theory, not a fact.”

    – sticker placed in biology textbooks in Cobb Country School District, Atlanta, Georgia; the same line can be found many other places

“Evolution is fact, not a theory.”

    – Carl Sagan, in the book that accompanied his television program Cosmos; the same line can be found many other places

To a philosopher of science, it is a strange debate indeed, for the epithet ‘theory’ seems to imply, to both parties, that there is some other sort of scientific thing that the view espoused by (neo-)Darwinians could be, and that being that sort of scientific thing (a ‘fact’) would lend it greater credence than it has in the eyes of the contemporary opponents of evolution.

Before I address this point further, I need to dismiss one kind of well-intentioned attempt to defuse the issue by drawing a distinction between the ‘fact of evolution’ and the ‘theory of natural selection’ (or more generally, theories about the mechanism of evolution). The former refers to the purported fact that members of certain species are the biological descendents of members of other (typically now extinct) species. The latter refers to ‘theories’ about the path or mechanisms by which new characteristics emerge and old ones disappear in a given species, or how one species ‘evolves’ into another. This distinction might help some people find an acceptable (to them) ‘middle ground’ between the two sides, but it will not resolve the issue for the vast majority of combatants: many (on both sides) will dispute even these more limited claims (e.g., the ‘fact of common descent’ or the ‘theory of natural selection’).

Now to the main point: the word ‘theory’ is apparently being used in what, to a philosopher of science, seems a rather odd way. Often, in everyday parlance, the term ‘theory’ refers to little more than “guesses strung together,” as William Jennings Bryan liked to say (about evolution). But in science, the term ‘theory’ means something more. It is notoriously difficult to say, with the sort of precision to which philosophers aspire, what it is to be a scientific theory, but I know of no philosopher of science who has thought carefully (or even casually) about the issue who believes that scientific theories are nothing more than hunches, or guesses, or mere opinion. Even radical social constructivism (not my cup of tea) will agree that something more needs to be true about a set of claims before it is properly labeled a ‘theory’. How specifically do theories go beyond mere hunches or guesses? This question is very difficult to answer, but in fact (fortunately) we do not need to answer it here. We need only to acknowledge two points, the first of which I have discussed in this paragraph: having an opinion regarding X is different from having a theory about X.

The second point goes the other way: theories can (and typically are) wrong in some way or other. Scientific theories come and go. Some of them have more credibility than others. Some of them face more problems and challenges and open questions than others. But none of them is immune to these things. Historians and philosophers of science have long given up on the idea that there are scientific theories that are somehow beyond doubt or question. The history of science makes the existence of indubitable scientific truths extraordinarily difficult to entertain.

Indeed, the lack of indubitable scientific truths extends even to very simple, apparently ‘merely factual’ claims, thus calling into serious question the distinction – insofar as it is supposed to have any evidential or epistemic import – between ‘theories’ and ‘facts’. Let’s consider an example. Does the earth orbit the sun, or vice versa? If there is a ‘factual’ answer to any question, surely this is one of them. But the ‘factual’ answer to this question has been intimately tied up with the fortunes of theory. The Ptolemaic theory of the planetary orbits was a very well-confirmed theory in the late middle ages and early modern period, and it implied that the sun orbits the earth. Along came Copernicus, with further confirmation from Galileo and ultimately Newton, and we arrived at a different ‘fact’: the earth orbits the sun. Along came Einstein, whose theory of general relativity calls into serious question the ‘absoluteness’ of accelerated motion, and therefore calls into serious question the very meaningfulness of the question itself. (The very definition of rotational motion within Einstein’s theory is notoriously problematic. I will not pursue the point further here.) It is somehow no longer even the right question to be asking, in the context of Einstein’s theory. Changes in science have a way of making certain ‘factual’ questions seem quaint.

I did not choose my example arbitrarily. Richard Lewontin, emphasizing the ‘factuality’ of certain aspects of evolution, wrote: “No person who pretends to any understanding of the natural world can deny these facts any more than she or he can deny that the earth is round, rotates on its axis, and revolves around the sun” (“Evolution/Creation Debate: A Time for Truth” Bioscience 31, 559). Ignoring Lewontin’s failure to appreciate the effect of Einstein’s theory on the question of what rotates around what (and he is a biologist, not a physicist, so we can cut him some slack here), there is a sense in which I agree with him: there is powerful theoretical and observational evidence for a wide variety of evolutionary claims (including many that Lewontin mentions). Insofar as we are asking scientific questions about the nature of this physical (specifically, biological) world, we can do no better than to appeal to that evidence; those claims are supported by scientific evidence as well as just about any scientific claim is support by scientific evidence.

Nonetheless – and nevermind for the moment the debate between evolutionists and their opponents – any claim that evolution is ‘fact’ must be tempered by the recognition that scientific ‘facts’ are intimately tied up with theory, and that scientific theories can and do change, often in surprising and even shocking ways. And when they do, the ‘facts’ that they imply can also change, often in surprising and even shocking ways. Quite often, the terms in which the old questions were posed and the old ‘facts’ were stated simply no longer make sense. The best we can usually do is to understand the ‘old facts’ retrospectively as some approximation to, or modification of, or merely phenomenal consequence of, the new ones.

On the other hand, any claim that evolution is ‘just a theory’ is equally misleading, and I’ll finish by briefly considering that point. If the claim is that evolution, like the products of science generally, is a ‘theory’, then one can hardly disagree, but this point ought not by itself drive one to find some alternative theory. Quantum mechanics is ‘just a theory’. Plate tectonics is ‘just a theory’. Both are empirically very well supported, and more important, there is no alternative view that is even remotely as well supported. This is not to say that they do not have their problems – there are, famously, some very difficult issues facing quantum theory, not the least of which is the failure, thus far, to account for the force of gravity in quantum-theoretic terms. But scientific theories always have open questions, and even conceptual and empirical problems. These questions and problems are never, by themselves, enough to consider the theory to be wholesale false.

And if the claim (‘evolution is just a theory’) is that evolution is nothing more than a string of guesses, then it is clearly false. The theory of evolution provides a model for the explanation of a significant amount of scientific observation. Is the explanation infallible? Clearly not – no scientific explanation ever is. Are there conceptual and empirical problems with the theory (problems that are celebrated in highly misleading ways by opponents of the theory)? Absolutely; and again, scientific theories always face such problems. But if you believe that the existence of some conceptual or empirical problems with a theory implies that the theory is wholesale false, or that the theory must be given up, or, even that some specific denial of the theory is true, I urge you to study the history of science carefully, for it suggests a very different conclusion. It suggests that the existence (and ultimate resolution, or dissolution) of such problems is the path to scientific progress, and that any prediction about the direction that theories will go in order to overcome the problems is extraordinarily likely to be wrong.

There is a great deal more to say, of course, about this debate, but my main point, here, is that the rhetoric involved (specifically the rhetoric of ‘facts’ and ‘theories’) is highly unproductive and misleading, and belies an almost tragic ignorance of the history of science on both sides.