A criticism which neo-Darwinists have frequently made of Intelligent Design is that it is not a “scientific” theory. ID, they say, explains the bacterial flagellum by saying “God [sic] made it”. However, they complain, it doesn’t say when God made it, how God made it, what material substrate God was acting on when he made it, etc. It therefore gives scientists nothing to go on, nothing to work with, nothing on which they can base experiments which could confirm or disconfirm the explanation.
In contrast, they believe, Darwinian explanations give scientists something to work on. The hypothesis that the flagellum slowly evolved, through a series of intermediate, functional steps, allows for testing. One can look for possible intermediate steps, e.g., the Type III secretory system, and confirm whether or not they exist in nature. One can study mutation rates and reproduction rates of bacteria, and calculate how many mutations have probably occurred over any given length of time, to see if enough time was available for the evolution of a flagellum, and so on. Thus, in their minds, Darwinism is a scientific theory, whereas ID is not.
It is clear that this line of argument presupposes a particular criterion for what makes an explanation scientific. To be scientific, a proposal, hypothesis or theory must be testable. We must be able to find evidence in nature that could confirm or disconfirm it.
Some ID critics narrow this down further, and say that scientific theories must be falsifiable. That is, ID cannot expect to be taken seriously as a scientific theory unless it is willing to specify a set of observations (taken directly from nature or resulting from experiments) that could prove it to be wrong. ID must say what it would take to falsify the existence of the proposed Intelligent Designer.
Now there has been a long debate over whether falsifiability is a good criterion to apply to scientific theories. The most frequently cited champion of falsifiability is of course Karl Popper, and as everyone here knows, many philosophers of science have disputed Popper’s claims. I do not propose to enter into the arguments here. I will say only that I find falsifiability, if not an absolute requirement of any scientific theory, at least a highly desirable element in a scientific theory, and I will refer readers to Popper’s writings if they want a detailed justification of this. A brief justification, in Popper’s own words, is available on-line.
For the purpose of my challenge here, however, my own view on falsification is irrelevant. Here I am going to agree, not out of personal conviction but purely for the sake of argument, with those neo-Darwinians who insist that scientific theories must be falsifiable. But then I am going to ask them to apply that standard to their own theory. I am going to ask them whether neo-Darwinism is itself falsifiable. I believe it is not, and that therefore, by their own criterion, it does not qualify as science.
Now I know that when this argument has been made in the past, neo-Darwinians have issued a standard answer. They say that Darwinian evolution is easily falsifiable. All one has to do is find a Cambrian rabbit, or any other fossil that is so far out of sequence that the creature in question cannot have evolved by stepwise Darwinian means. This, however, for reasons given by others, is not an adequate answer. Many ID proponents have no problem with the notion of common descent. They have no problem with the notion that one creature has been used as the basis of a subsequent and more advanced creature. They therefore do not reject “evolution”, and they have no desire to find a Cambrian rabbit or a Jurassic monkey. What they reject is the Darwinian “chance plus natural selection” explanation of evolution. So what neo-Darwinians are being asked, when they are being asked about falsification, is not “What would falsify common descent?” It is: “What would falsify your theory that small, incremental steps, which occur due to genetic accidents, can be combined into useful new structures, up to and including the creation of entirely new functional body plans?”
This is the question that I am putting to neo-Darwinists today. What would it take to falsify your belief, for example, that land creatures are ultimately modified fish, transformed by slow, tiny and wholly fortuitous steps from gill-breathers to lung-breathers? What genetic, developmental, or other evidence would you accept as a demonstration that fish could not have become land-dwelling creatures via purely Darwinian means? What genetic, developmental or other evidence would you accept as a demonstration that the camera eye could not have developed by purely Darwinian means?
When ID people read Darwinian literature, we get the strong impression that Darwinians do not ask whether Darwinian means are capable of producing their alleged effects. They appear to be asking only how Darwinian means did so. And when one possible evolutionary pathway is shown to be impossible on scientific grounds, another pathway, always within Darwinian assumptions, is put forward to replace it. At no point, as far as we can see, do Darwinians ever say: “Well, maybe we have been wrong all along. Maybe Darwinian explanation cannot account for evolutionary change.” And so, when we read in Darwinian polemics that ID is “unscientific” because it will not commit itself to any model of the designer’s action specific enough to be falsified, we are rather irritated by the apparent double standard, because we have not seen such a falsifiable model in the Darwinist literature.
So, again, here is the challenge to neo-Darwinians: What would it take for you to concede, not just that this or that proposed evolutionary pathway is wrong, but that the entire Darwinian explanation of evolutionary change is wrong? What evidence would it take for you to concede that small, random, stepwise changes cannot produce the specific macroevolutionary effects that the fossil record appears to record? And the corollary question is: If you are unwilling to specify in advance what it would take to falsify neo-Darwinian mechanisms, are you willing, here and now, either to admit that neo-Darwinism is not a scientific theory, or to drop the requirement of falsifiability which you have laid upon ID?