Paul and I have discussed this topic before in email, so I'll
post some of my comments.
Paul's objection 1.D.: No known instances of CSI produced by natural
selection are known.
Let's explore CSI a little closer. We have two criteria that
combine to yield Dembski's CSI: complexity at or above 500
bits and match to a specification. I will call this CSI_500
in order to introduce a slightly different perspective on CSI.
Complexity is obviously distributed along the ordinal line of
bits. Solutions to particular problems may represent CSI at a
lower threshold than Dembski's step function of 500 bits
proposes, but this should be clearly noted via use of a
modifier to relate the level of complexity involved, like
"CSI_250" or "CSI_50".
No one questions the ability of natural selection to produce
solutions at lower complexity levels. Whether one admits
"CSI_50" or "CSI_250" as supported by the available evidence
does not matter. What matters is that this level of
performance is properly credited to the action of natural
selection.
Natural selection, though, is notoriously difficult to
empirically isolate as a mechanism of action. The level of
evidence needed to both implicate natural selection and to
exclude genetic drift is high. Indirect evidence, such as the
presence of linkage disequilibrium in a population, serves as
an indicator of the action of natural selection, but
biologists tend to want to see a clear relation between a
cause of selection and an effect in distribution of traits in
a population.
Taking it as possible that adaptive features of organisms are
designed and installed by an intelligent agent via a mechanism
other than natural selection means that we cannot use as
examples of the efficacy of NS those phenomena in question,
unless and until we have in hand the same kind of evidence
that suffices for Galapagos finch beak changes. This may
simply never be available. But if all that is available for
the alternative hypothesis of ID is the simple fact of
CSI_500, then I doubt that many biologists will feel compelled
to exclude natural selection as a live possibility on those
grounds alone.
What we are then left with is an argument that we should
exclude from consideration a mechanism of generating solutions
that we can observe to happen in modern populations and which
produces CSI at lower complexity levels during our brief and
spotty periods of observation in favor of a mechanism which
has no independent evidence of operation and which is not
currently observable. (That is, the intelligent agent
putatively responsible for the biological system under
question is not known from current observation or from
independent evidence of the period in question.) I think that
such an argument will find it rough going to convince
knowledgeable people of its merits.
We should do the calculations to determine the CSI level of
various examples of NS in action, or general "descent with
modification" in action. Things like bacteria digesting nylon
with novel enzymes or the emergence of the impedance-matching
apparatus of the mammalian middle ear need to be explored
quantitatively. A spread of CSI levels may indicate an
approach to the CSI_500 level that Dembski sets, and indicate
that no essential qualitative difference exists between the
capability of natural evolutionary algorithms and intelligent
agency.
Note: Dembski does discuss justifying CSI at lower bit levels
than the universal small probability bound of 500 bits in TDI.
If the universal small probability bound is met, though,
justification is simpler.
Also, it would focus the discussion wonderfully if either Paul
or Bill would provide a worked example of running some scenario
involving natural selection through the Design Inference. We
are urged to "do the calculation" at the end of TDI, but there
seems to be a dearth of serious examples with a complete set
of calculations per each.
Wesley
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