Bacterial Flagella and Dembski’s Case for Intelligent Design: Closing Arguments
Earlier in this critique we outlined
Dembski’s case for the proposition - bacterial flagella are
intelligently designed - as follows:
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The bacterial flagellum displays specified complexity.
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Specified complexity in biotic systems
cannot be generated by the Darwinian mechanism,
which relies on chance.
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Therefore the bacterial flagellum must
have been intelligently designed - that is, it could
have been actualized only with the assistance of form-conferring interventions
by an unembodied intelligent agent.
We then focused our attention on the first of
these statements and asked, Does the bacterial flagellum exhibit “specified
complexity” as it is defined by Dembski? In order to
do that it would have to be a) sufficiently complex, and b) specified.
Is the bacterial flagellum sufficiently
complex? Using Dembski’s own criterion, only if the probability of its being
actualized by the joint action of all natural causes is less than the universal
probability bound. Dembski attempted to demonstrate this to be true by treating
the bacterial flagellum as if it were a discrete combinatorial object
actualized by the pure chance gathering of 50 of the right kinds of proteins
(and in the correct proportions) at some spot in the vicinity of the cell wall
and plasma membrane of E. coli and then, again by chance, happening to
configure themselves into a functioning rotary propulsion system for this
bacterial cell. The only natural formational process that Dembski
considered in his probability computation was self-assembly by pure
happenstance.
We reject that argument as being a totally
unrealistic caricature of how the flagellum is actualized and an approach that
totally ignores the role of the bacterial genome in coding for all of the
structures and functions that contribute to the nature of E. coli. E. coli
bacteria possess flagella, not because flagella self-assemble and self-attach
to the cell membrane, but because the genome of E. coli came to include in its
genetic library the coded instructions for growing the flagellar
propulsion system. Dembski’s case for the complexity (as he defines it) of the bacterial flagellum
fails.
Is the bacterial flagellum specified? Using
Dembski’s own criterion, only if it exhibits a pattern that is
detachable - wholly independent of the event that produced it. Appearing to set
aside his laboriously crafted formalism regarding the specification and
detachability requirements, Dembski simply asserts that in the case of biological systems specification always refers to function,
and declares that biological functions are inherently detachable from the
particular biological systems that instantiate them.
We reject that argument for a number of
reasons. First, the general principle that biological function counts for
specification was never established by Dembski. Second, his application of this
principle appears to be entirely ad hoc. Dembski provides no systematic means
for concluding that the function of the flagellum should count as a detachable
specification while other equally remarkable biological functions of E. coli go
unmentioned. If none of the other biological functions of the bacterium count
as sufficiently remarkable to serve as a detachable specification, then neither
should the function of the flagellum. Dembski’s case for the specification (as he defines it) of the flagellum fails.
Finally, there is the broad question
concerning Dembski’s rhetorical use of key terms like complexity
and specification. On the question of
specification, for instance, Dembski asserts that, “no biologist I know
questions whether the functional systems that arise in biology are specified.” The question is, however, Is Dembski using the term “specified” in the same way
as the biologists he has in mind? The answer, I believe, is, No. Dembski treats
the presence of biological function as if it constituted a detachable pattern
independent of the organism under scrutiny. For Dembski, biological function is
one of the qualities of a complex organism that only intelligent intervention
could produce. For biology, on the other hand, biological function plays nearly
the opposite role. Biological function is the very capacity of an organism that
gives it the ability to respond to its environment in the manner described by a
rich menu of dynamically changing fitness functions, a responsive phenomenon
that lies at the heart of evolutionary dynamics.
A similar concern about Dembski’s use of key
terms arises in regard to the meaning of “complexity.” After quoting a number
of prominent biologists regarding the scientific challenge of accounting for
the information now resident in complex biological systems, Dembski asks, “But
what sort of information are they talking about?”He soon answers his question in a way that appears to place their concern
squarely in his own design-theoretic court. “I submit that what they have in
mind is specified complexity, or what equivalently we have been calling ...
complex specified information. Certainly the complexity of biological
information is not at issue.”But of course this bold assertion could be true only if Dembski is using the
term “complexity” in the same way as the persons he quoted, which seems not to
be the case. As we saw in our general considerations on complexity, the
“complexity” that Dembski computes is a property, not of some biotic system
itself, but of the means by which it becomes actualized. That is why, for
instance, he treated the bacterial flagellum as if it were a chance-assembled
discrete combinatorial object and judged its complexity on the basis of the
probability of its coming to be actualized by nothing more than pure accident.
Most biologists, on the other hand, use the term “complexity” as the name of
something quite different - a structural or functional quality of the biotic
system itself.
But “specification” and “complexity” are not
the only terms that Dembski, like other leaders of the ID movement, employs
rhetorically with unorthodox meanings. Recall, for instance, that to be
“intelligently designed” is, in effect, to be assembled
with the aid of form-conferring (or information-infusing) action performed by
an unnamed and unembodied choice-making agent. Recall also that when
this unembodied intelligent agent brings about a
naturally impossible outcome, it is not a “miracle.” And recall that
“chance hypothesis” most often means all hypotheses, postulates
and theories concerning the natural causation of events. The case
for ID relies on a web of words that have been assigned extraordinarily unusual
meanings.
Given this character trait of ID literature,
including such works as Dembski’s No Free Lunch,
would it not be appropriate to suggest that Dembski pause to reflect on his own
admonition regarding the need to use words appropriately, consistently, and
with precision to avoid the charge of equivocation? Says Dembski,
“The fallacy of equivocation is the fallacy of speaking out of both sides of
your mouth. It is the deliberate confusing of two senses of a term, using the
sense that’s convenient to one’s agenda.”
On this point Dembski
and I agree. Ironically, however, I find Dembski’s
rhetoric to be riddled with the very equivocation that he condemns.
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| Contributed by: Dr. Howard Van
Till
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