Stephen : Behe uses "irreducible complexity" in the same sense of "complex" that
Darwin used it:
"Darwin knew that his theory of gradual evolution by natural selection
carried a heavy burden:
`If it could be demonstrated that any complex organ existed which could
not possibly have been formed by numerous, successive, slight
modifications, my theory would absolutely break down.' (Darwin C.,
"Origin of Species", 6th ed., 1988 reprint, p154).>>
Behe defines 'irreducibly complex' as 'could not have evolved' and then calls something 'irreducibly complex' and claims that it therefor could not have evolved. Yet the conclusion is based upon whether or not all irreducibly complex systems could not have evolved. That's were Behe is confusing the two. He has not shown that evolution could not have lead to the irreducibly complex system.
Stephen : <<Well, for starters, a system that is irreducibly complex. By irreducible
complexity I mean a single system composed of several well-matched,
interacting parts that contribute to the basic function, wherein the removal
of any one of the parts causes the system to effectively cease functioning. >>
Fine but this does not mean that the system could not have evolved. There have been several examples on the net showing this to be a logical fallacy. The end effect might be irreducibly complex in that removing one part leads to a collapse of the whole system, but that does not mean that it had to be like this during the evolutionary development.
Stephen : <<An irreducibly complex system cannot be produced directly (that is, by
continuously improving the initial function, which continues to work by the
same mechanism) by slight, successive modifications of a precursor system,
because any precursor to an irreducibly complex system that is missing a
part is by definition nonfunctional. >>
By definition... You proved my point. Behe defines a circular argument and denies as such the possibility that a 'precursor to an irreducibly complex system is per definition non-functional'. But that does not need to be so.
Stephen : <<An irreducibly complex biological system, if there is such a thing, would be a powerful challenge to Darwinian evolution. Since natural selection can only choose systems that are already working then if a biological system cannot be produced gradually it would have to arise as an integrated unit, in one fell swoop, for natural selection to have anything to act on.">>
But that is based upon a circular argument presuming something which has yet to be shown. Yes, removing a part of an irreducibly complex system will cause the system to fail. Look at at brick archway, removing any one will likely collapse the system and yet they were not all placed in position all at once. That by itself lays to rest Behe's poor argument.
Stephen : <<If one quibbles about Behe's allegedly "colloquial" use of the word "complexity" while granting Darwin the right to use the word "complex" in his famous test of his theory, then one has rendered Darwin's theory unfalsifiable in principle.>>
Not at all. Behe showed that removing a part of an irreducibly complex system will lead to a failure, but he did not show that a precursor of the system could not have existed.
Stephen : <<
This just confirms Behe's argument. Obviously a human intelligent designer
can make irreducibly complex structures. The question is whether a `blind
watchmaker' using only natural processes can do it.>>
Behe's argument is based on the unsupported assumption that it cannot happen. But he fails to provide evidence of such.