Tuesday, May 29, 2007

Equivocation--Part 2

In the last post, I talked about equivocation, the logical fallacy in which the meaning of a term changes between the premise and the conclusion. The example in that post was an instance of equivocation (with regard to the term 'secular') of which Richard Dawkins was guilty. Today, I want to point out a much more common example of this fallacy, and that with regard to the term 'evolution.'

It is increasingly being claimed that "evolution is a fact." Now, when people say this, they may mean a variety of things, but at the end of the day, we are meant to believe and accept two things: 1) the idea that neo-Darwinian evolution--and particularly natural selection acting upon random mutations--is the explanation for the diversity of all life (extant and extinct), and 2) that this explanation is so evidentially-supported that it is above critique and that all rival theories or even criticisms of it are therefore unscientific.

Strong claims these, so strong that one would expect a whole lot of evidence to support them. But invariably, the evidence trotted out will be cases of what's known as micro-evolution, that is, changes within a species. "Americans are 6 inches taller on average than 100 years ago." "Beak sizes of finches in the Galapagos change in response to variations in precipitation." "The ratio of melanistic to normal Peppered Moths changed in response to the Industrial Revolution."

Each of these examples has its own problems, even with regard to how well it supports micro-evolution. Nonetheless, that micro-evolutionary changes do occur in the plant and animal kingdoms is completely non-controversial. So, too, is the idea that some speciation may occur, whereby two populations of a single species may become separated (geographically, behaviorally, morphologically, physiologically, or whatever) to the point that they are no longer capable of interbreeding and warrant status as separate species.

But the idea that all life is linked to a single common ancestor (through natural selection acting on random mutations) is a different thing altogether, and is generally referred to as macroevolution. That macroevolution occurs (or ever has occurred) is entirely without evidential support. Indeed, all of the evidence--as from the fossil record--indicates otherwise. The fossil record shows life forms arising suddenly, fully formed, perfectly adapted for their environment and ecology, and remaining unchanged throughout their tenure. Belief in macroevolution involves an unwarranted philosophical presupposition (naturalism), a leap of faith, and a correspondingly unfounded extrapolation from microevolutionary evidence to macroevolutionary claims. As Phillip Johnson has it (in Darwin on Trial)...
Why do other people, including experts whose intelligence and intellectual integrity I respect, think that evidence of local population fluctuations confirms the hypothesis that natural selection has the capacity to work engineering marvels, to construct wonders like the eye and the wing? Everyone who studies evolution knows that Kettlewell’s peppered moth experiment is the classic demonstration of the power of natural selection, and that Darwinists had to wait almost a century to see even this modest confirmation of their central doctrine. Everyone who studies the experiment knows that it has nothing to do with the origin of any species, or even any variety, because dark and white moths were present throughout the experiment. Only the ratios of one variety to the other changed. How could intelligent people have been so gullible as to imagine that the Kettlewell experiment in any way supported the ambitious claims of Darwinism?
This being the case, it seems much easier (if you are an evolution activist) to suppress this problem. Why bother to distinguish between microevolution and macroevolution? It makes a whole lot more sense to equivocate, to use 'evolution' both in the premises (where we'll trot out evidence for microevolution) and in the conclusion (where what we really have in view is another thing entirely, macroevolution).

But from now on, the astute readers of this blog will be able to see through this fallacious ploy on the part of evolutionary scientists, educators, and activists.


Jack Niewold said...

Rick, these are very helpful posts. Keep them coming. I am learning a great deal from your blog!

Steven J. said...

Every evolutionist I know of means, by "evolution is a fact," either that "change in the frequency of inheritable traits in a population" is a fact (an uncontroversial claim, I think), or else that "common descent with modification" (the idea that humans share ancestors with other species from chimpanzees and crabgrass) is a fact.

While the existence of natural selection is a fact in its own right, evolutionists do not generally say that it is a fact that natural selection is the main cause of evolution, or even that it is the main cause of adaption.

Note that Darwin came to the conclusion of common descent (that the resemblances among living species were literally family resemblances, inherited from common ancestors) before he worked out the idea of natural selection. During the early 20th century (the so-called "eclipse of Darwinism"), evolution was commonly accepted as a fact by scientists, while natural selection was widely held to be an unimportant part of the explanation for why evolution happened. So "evolution" and "natural selection" are separate ideas, and one could be correct without the other, or be better evidenced than the other.

A side note, although it is not in response to anything actually in your blog post: a "theory" in science is a testable explanation for some phenomenon. A "fact" is a statement that is so supported by evidence that it would be perverse not to provisionally (subject to possible future evidence to the contrary) accept it as an accurate description of the real world. These are not separate levels on some epistemic ladder.

It has been argued (and it seems right to me, although some philosophers of science disagree) that the same statement can be both a "theory" (an explanation for some data, as heliocentric astronomy is a theory to explain the apparent motions of the planets as viewed from Earth), and a "fact" (as heliocentric astronomy has been for some centuries) which requires another "theory" to account for why it exists (e.g. the theory of gravity).

-- Steven J.

Rick Gerhardt said...

Hi steven j. Thanks for reading.

Your post serves to remind me that yes, there is a good deal of equivocation not only upon the term 'evolution' but also on the word 'fact.' In its more technical usage, fact is synonymous with datum, an observable bit of information about which we can draw inferences, make generalizations, or otherwise explain. 'Fact' is also frequently used in a less technical sense, to express a degree of certainty. (I generally find it disingenuous when scientists--who should know and exclusively use the technical meaning--use this word in the epistemological sense.)

I disagree with you about the place of Darwin in our modern understanding. True, he hypothesized common ancestry, but that audacious claim would have gained no credibility without a plausible mechanism, which he supplied in the form of natural selection.

Natural selection remains the textbook explanation for the diversity of life, that to which neo-Darwinists appeal to express their certainty that evolution is true. (Since Darwin's time, of course, genetic mutation has been added as the raw material upon which natural selection works.) Not only is this still what is taught (as the explanatory mechanism), but this is the reason that neo-Darwinists took such exception to Gould and Eldredge's dismissal of the gradualistic scenario. Gould and Eldredge both believed in common ancestry, but could offer no mechanism to explain their theory of punctuated equilibrium. They had far more evidence (especially from the fossil record) on their side, but no mechanism. Neo-Darwinists have far less evidence going for them, but at least they have a mechanism to espouse--natural selection working on genetic mutation.

But I fear that I have still not addressed the most serious error in thinking that you have exposed in your comment. You suggest that many evolutionists mean by "evolution is a fact" that it would be perverse not to accept Darwin's audacious claim of common ancestry even without a plausible mechanism. They seem to be saying that common ancestry (of all life) constitutes the undeniable nature of reality. But (don't you see) this makes the all-the-graver mistake of confusing the facts that need explaining (such things as the universality of the genetic code, for example) with a particular theory, one attempt at such explanation.

That all life contains the same genetic code could be interpreted as consistent with common ancestry. But it accords just as nicely with the typological view that Darwin sought to supplant--the view that living things existed as distinct types because they were created fully adapted (and that the sorts of transitions that Darwin hypothesized were incoherent and nonsensical, since the divisions in nature were rooted in necessity). Indeed, proponents of Intelligent Design, Old-Earth Creationism, and Typology would all have predicted that all living things share the same biochemical and genetic make-up. (Darwin's theory was never meant as an explanation for the similarity of all life but as a way of explaining how the differences came to be. Though we now know that chimps and humans are genetically 96% similar, we are still no closer than ever to explaining why these two species are nonetheless so very different from one another.)

So you see, common ancestry remains only one theory for explaining the observable data that all life on Earth shares a common biochemistry. To confuse the data (common biochemistry/genetics) with one of the several explanatory theories (common ancestry) is really a sophomoric error in reasoning. You're absolutely right, though--many modern evolutionists are guilty of this very thing.

Thanks again for the comment!