Notes on Draper's Article on Behe's Design Argument, Part 2: Three Bad Criticisms

Here is the second installment on Paul Draper's critique of Behe's design argument in his "Irreducible Complexity and Darwinian Gradualism: A Reply to Michael J. Behe", Faith and Philosophy 19:1 (2002), pp. 3-21.


Draper points out that three common criticisms of Behe's irreducible complexity argument miss the mark.

I. Bad Objection #1: Other Biochemical Systems are Reducibly Complex and Evolvable
First, some have argued that lots of biochemical systems exhibit redundancy, which shows that such systems are not irreducibly complex. But Draper points out that this doesn't refute Behe's argument. For recall that Behe isn't committed to the claim that all biochemical systems are irreducibly complex, but rather the weaker claim that at least some are, and that some of these (viz., those that are very complex) could not have evolved through gradualistic evolutionary processes. Behe isn't your standard creationist: he thinks the evidence for the key evolutionary theses of common ancestry and descent with modification are persuasive. He also thinks that gradualistic evolutionary mechanisms can account for many biochemical structures as well -- viz., those that are reducibly complex. But the authors in question don't address the particular examples of biochemical systems that Behe argues are irreducibly very complex (e.g., the bacterial flagellum).

II. Bad Objection #2: Very Simple Irreducibly Complex Systems are Evolvable
Second, a number of people -- most prominently, cell biologist and devout Catholic Kenneth Miller -- have argued that certain structures are irreducibly complex, and yet have clearly evolved gradually. So, for example, MIller points out that the three-boned structure within the inner mammalian ear is irreducibly complex, and yet we have excellent evidence that it evolved via an indirect evolutionary pathway from parts of the jaws of reptilian evolutionary predecessors. But this doesn't refute Behe's argument, either. For recall that Behe argues that while no irreducibly complex system can evolve via a direct evolutionary pathway, he grants that a relatively simple irreducibly complex structure can evolve via an indirect evolutionary pathway: "Even if a system is irreducibly complex (and thus cannot have been produced directly), however, one can not definitively rule out the possibility of an indirect, circuitous route. As the complexity of an interacting system increases, though, the likelihood of such an indirect route drops precipitously." Behe, Darwin's Black Box, P. 40.

In short, the first two popular criticisms of Behe's argument miss the mark. For these are based on examples of reducibly complex systems and simple irreducibly complex systems that have arisen via gradualistic evolutionary pathways. But to touch Behe's argument, one needs an example of an irreducibly very complex system that has arisen via a gradualistic evolutionary pathway.

III. Bad Objection #3: It's Just Paley's Bad Analogical Design Argument in New Packaging
Finally, a number of people have claimed that Behe's argument is just a re-statement of Paley's design argument, and since Paley's version falls prey to Hume's and Darwin's criticisms, so does Behe's. But Draper argues that while Behe has contributed to this perception (he explicitly identifies his argument with Paley's), it is nonetheless a misleading and uncharitable criticism. This is because most people think of Paley's argument as the one Hume attacked, viz., an argument from analogy, and having the following form:

1. Human artifacts are intelligently designed.
2. The universe, or some of its parts, resemble human artifacts.
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3. Therefore, the universe, or some of its parts, were (probably) intelligently designed.

But as Elliot Sober has argued[1], while Paley talked about an analogy between watches and organisms, his actual argument wasn't itself an argument from analogy. Rather, it was an abductive argument to the best available explanation:

1. Some natural systems (e.g., the human eye) are mechanically ordered (i.e., they exhibit the same sort of order as watches and other machines produced by human beings).
2. Intelligent design is a very good explanation of mechanical order.
3. No other explanation (or no equally good explanation) of mechanical order is available.
4. Every instance of mechanical order has an explanation.
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5. So, some natural systems were (probably) intelligently designed.

But if so, then at least three things can be said on behalf of Behe in response to the third criticism. First, while the critics may be right that Hume refuted the analogical version of the design argument, they're wrong to think that Hume refuted Paley's design argument. For his is the abductive version, and Hume's criticisms don't refute it. And if Behe is defending Paley's abductive argument, it follows that it's not enough to point to Hume to answer Behe's argument.

Second, Behe has made a genuine contribution to improving Paley's argument by articulating an account of mechanical order mentioned in the premises, viz., his notion of irreducible complexity.

The previous point brings us to the third. For while many would argue that Darwin refuted Paley's abductive argument (even if Hume did not), Behe has strengthened Paley's argument in a way that requires more of a response than just pointing to Darwin. For Darwin and subsequent scientists have only shown how biological systems larger than biochemical structures can evolve gradually. But that's consistent with the claim that the smaller, biochemical structures cannot evolve gradually. And as we saw in a previous post, Behe has argued just this: certain biochemical structures (e.g., the bacterial flagellum) are irreducibly very complex, and thus couldn't have arisen via direct or indirect evolutionary pathways. Therefore, we have another reason for thinking that Behe's argument can't be dismissed by just pointing to earlier critiques of the design argument.

We've just seen three common criticisms of Behe's argument that don't seem to work. In the remaining posts in this series, we'll take a look at three criticisms that seem telling.
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Notes
[1] Philosophy of Biology (Boulder, CO: Westview Press, 1993), pp. 34-35. Draper's reference, "Irreducible Complexity and Darwinian Gradualism", p. 7.

7 comments:

Tommy Holland said...

Behe feels that common descent simply works, and works most of the time. He implies that the Intelligent Designer only occasionally has to step in--one gets the impression that the Designer has to do so on an extremely reluctant basis--and work its magic to give a poor immobile bacteria its flagella.

Meanwhile, Young-Earth Creationists think that common descent never works at all. And yet they hold up Michael Behe as their poster-child of science, and Behe doesn't bother to correct them.

Bad science makes for strange bedfellows.

Tommy Holland said...

One more comment:

Has Behe ever speculated on how much time elapsed between a flagella-less bacteria and a bacteria that's fully mobile?

If the flagella appeared instantaneously on the southbound-end of a northbound bacteria, then he's arguing magic, and it's disengenuous to ask for intermediate forms to falsify his theory.

On the other hand, if the flagella appeared gradually over several generations, each generation building on the previous with additional parts, then he's arguing for common descent--albeit a predeterministic descent. So what's the difference between Common Descent with the End firmly fixed in mind, and plain old ordinary Common Descent?

And since Behe accepts non-deterministic Common Descent, how can he tell the difference? Apparently its based on complexity. If Behe thinks something is ordindarily complex, then ordinary Common Descent is just fine. But if something is extraordinarily complex like a flagella, then Intelligent Design is required. This makes Behe's value judgements the standard by which complexity is measured.

zilch said...

Tommy Holland, you say:

Behe feels that common descent simply works, and works most of the time. He implies that the Intelligent Designer only occasionally has to step in--one gets the impression that the Designer has to do so on an extremely reluctant basis--and work its magic to give a poor immobile bacteria its flagella.

Indeed. And strangely enough, the Intelligent Designer only steps in to give a helpful tweak to precisely those structures whose evolutionary origins happen not to be pretty fully elucidated yet. The correspondence is too unlikely to have resulted by chance: the Intelligent Designer must have known at the Beginning which structures we would eventually have trouble explaining, and He, She, or It twiddled and diddled only those particular structures. That proves that the Intelligent Designer is God.

Meanwhile, Young-Earth Creationists think that common descent never works at all. And yet they hold up Michael Behe as their poster-child of science, and Behe doesn't bother to correct them.

That's another disarming feature of ID: it's nothing if not egalitarian. Their big tent is open to everyone: Christians, Jews, Muslims, Moonies, even a few weird atheists; OEC's, YEC's, evolutionists, deniers, you name it. The fact that most if not all of these positions are mutually exclusive doesn't bother them. Ya gotta love that ecumenical spirit!

Russ said...

exapologist

Thanks for the nice distillation.

Regarding Behe's ID-related arguments, I think they fail at a rather fundamental level, a failure which Behe himself admitted under oath at the Dover trial.

Implicit in Behe's claims of knowing what phenomena evolutionary processes are in principle not capable of producing, is the claim that he possesses full knowledge of all phenomena that evolutionary processes are capable of producing. However, on the stand at Dover, when confronted with a large number of peer-reviewed articles concerning evolution of his irreducible complexity mainstays of bacterial flagella, and blood clotting mechanisms, he confessed that he was not aware of them. Couple this with his ignoring the important evolutionary mechanisms of exaptation and scaffolding in "Darwin's Black Box," and we see that Behe's claim of possessing an exhaustive understanding of what can be produced through evolutionary mechanisms fails.

Behe does not understand even a fraction of what would be required before proposing his ID hypothesis. Indeed, if he did, the demands placed on him by the world body of science would be so great, that he would have no time at all for his Discovery Institute nonsense.

Dr Funkenstein said...

Behe feels that common descent simply works, and works most of the time.

Behe's harder to pin down on this than you think - although as far as I remember he has stated there doesn't seem like another obvious explanation for eg shared pseudogene mutations, he whistles a slightly different tune at other times.

On a Christian radio show a while back, he seemed to give credence to the idea that YEC was a legitimate position for Christians to approach biology from (I'd have to search for the exact quotes, but it was statements to that effect).

I'm pretty sure he also contributed to Pandas and People, which quite clearly promotes denial of common ancestry.

I think he's also said that he feels that many of his common ancestry denying cohorts in the ID movement are more expert when it comes to the evidence regarding common ancestry than he is.

Badger3k said...

For objection 2 - some simple irreducibly complex...

First off, wtf? If it can be shown to be reducible, no matter if it is said to be "simple: or "complex" (whatever that means), then it is not irreducible. We've seen proposed evolutionary pathways for such things as the inner ear, eyes, and the blood clotting cascade (things that Behe admitted to not finding out about, assuming you believe his testimony).

I'm sure that the next posts will have dealt with the problem that his "explanatory filter" doesn't work, or that the analogies where he likens ID to SETI fall apart with a slight breeze.

exapologist said...

Hi Badger3k,

First off, wtf? If it can be shown to be reducible, no matter if it is said to be "simple: or "complex" (whatever that means), then it is not irreducible.

Careful: The objection isn't that some irreducibly complex structures are reducible, but rather that some irreducibly complex systems are evolvable.

But Behe allows that irreducibly complex systems are evolvable in principle. According to Behe's original definition of 'irreducible complexity', an irreducibly complex system is one "composed of several well-matched, interacting parts that contribute to the basic function, wherein removal of any of the parts causes the system to effectively cease functioning" (Darwin's Black Box (New York: The Free Press, 1996), p. 39). Behe thus doesn't build into his definition of 'irreducible complexity' that it can't be gotten via evolution. He gives independent argument for that. I sketch his argument in Part I of this series. As I mention there, Behe grants that it's possible in principle (though highly improbable) for an irreducibly complex system to evolve: "Even if a system is irreducibly complex (and thus cannot have been produced directly), however, one can not definitively rule out the possibility of an indirect, circuitous route. As the complexity of an interacting system increases, though, the likelihood of such an indirect route drops precipitously." Behe, Darwin's Black Box, P. 40.

I discuss this in Part I, but very briefly: Behe distinguishes between direct and indirect evolutionary pathways. And his argument is that no irreducibly complex biochemical system can be created via a direct evolutionary pathway, for any precursor to an irreducibly complex system is by definition non-functional. And while it's possible in principle to create an irreducibly complex biochemical system via an indirect pathway, the probability of this happening is too low to be plausible for systems that are very complex (and there are such systems).