Step-wise downward and lateral changes are also part of evolutionary theory,
since they're part of run-of-the-mill genetics. (This is one difference
from epicycles: the existence of these alternate mutation possibilities is
fairly obvious, whereas the existence of epicycles was purely speculative.)
Also, to observe that this argument is fallacious is neither to claim nor
imply that neo-Darwinism is unfalsifiable. Those are independent issues.
BTW, thanks for posting Behe's comment basically agreeing with my point, I
believe (which encourages me wrt the ID movement: given that I haven't read
Behe's book, I've relied on articles and discussions here, and this is the
first time I've come across this [what seems to me] major and insightful
concession), but then adding that the probability of producing a given IC
system drops dramatically if a more circuitous incremental path is required.
I think this may be true, actually, but the implications are unclear, since
the prior probabilities are unknown. (E.g., if a circuitous path reduced
the likelihood of producing X by 5 or 10 or n orders of magnitude, producing
X may still be extremely likely.)
Also, I say only "may be true" because it's hard to know just what the
change in odds is. A more complicated pathway to a given result seems a
priori much less likely than a simple pathway. But given that there are
indefinitely many, perhaps literally infinitely many complex pathways (in
principle, not in concrete practice), it's hard (for me, anyway) to see
accurately just what the effect is on the overall probability of producing
X.
I think what one really needs to make this argument pack a lethal punch is
either (1) a good statistical analysis of all the different possibilities,
which would be an ENORMOUS (and perhaps impossibly speculative) task, I
think, or (2) an argument not merely from IRREDUCIBLE complexity, but
something like IMMUTABLE complexity, complexity such that change in any
direction -- a reduction, an increase, a substitution, a reversal, etc.-- on
any scale occurring in nature (one base pair, a contiguous group of base
pairs, etc.) would results in an overall dysfunctional system. Now THAT
would be an interesting proof, were it ever soundly devised.
Remember, Steve, I'm entirely open to ID theory being true. I'm simply not
open to bad arguments to that conclusion. And I think Hoyle's argument (as
summarized, at least) is a bad one.
John