ID: Irreducible Complexity
- Dear Group:
Below is the second of a series of extracts from my article "Intelligent Design theory: the way forward?", Stimulus, volume 9, issue 2, May 2001, pp.8-13.
I invite you to comment on whether or not I have been accurate and fair in this comment on Behe's work.
Intelligent Design: Irreducible Complexity
The concept of Intelligent Design may be considered to be the intellectual offspring of William Paley, the English theologian and moral philosopher, who in 1802 published Natural Theology, or Evidences of
the Existence and Attributes of the Deity. Here Paley argued from analogy, suggesting that if one happened to find a watch (rather than a stone) it was obvious that there must somewhere be a watchmaker.
From this he went on to claim that the order and design of the natural world necessarily presupposed a grand design and thus a Designer.
The modern successor to Paley is Michael Behe (pronounced "BEEhee"). In his book Darwin's Black Box56 he defined an irreducibly complex (IC) system as one 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. (He used a mousetrap as an illustration.) Behe asserted that
such systems cannot evolve directly by a series of small modifications, each of which is a slight improvement to some initial system. He briefly mentions that indirect circuitous development is possible,
but he asserts that this is tremendously unlikely. Also, it would be tremendously unlikely for any complex system to arise naturally in one fell swoop by mutation. His book gives details of several
complex biological systems. He claims that these systems are IC, and that the scientific community has no Darwinian explanation of them. He concludes that these aspects of life did not evolve, and
therefore by default these are the result of Intelligent Design. Behe was careful to say nothing about a Designer. It was only later that it became public knowledge that he is a Roman Catholic.
A weakness of Behe's thesis is that the determination that a given system is IC depends on the present state of knowledge. Hence his argument is analogous to a "God of the gaps" explanation. Numerous
biochemists have disputed Behe's claim that his various complex systems are in fact irreducible. For example, I refer to Don Lindsay6, who noted that IC systems had already been discussed by H.J. Muller7
in 1939, and that Muller had argued that evolution would routinely cause such systems. Lindsay notes that Behe assumes that evolution always progresses by addition, whereas it is well known that it often
occurs by subtraction. Further, Shanks and Joplin8 give several examples of biochemical systems that continue to function when apparently crucial elements are missing. That article says, "It is a
hallmark characteristic of evolved biochemical systems that there are typically multiple causal routes to a given functional end, and when one route fails, another can take over." (I should mention that
Behe9 has responded to the Shanks and Joplin article, and his response has been further criticized in further internet forum discussion. The argument involves whether or not elements of the systems
discussed by Shanks and Joplin are sufficiently well matched.) In particular, Behe spent his Chapter 4 arguing that the blood clotting cascade could not be reduced, but Lindsay says that there are lab
mice from which several parts of the clotting cascade have been removed, and they seem quite normal. Lindsay also gives internet links to evidence that the immune system is not IC, and says that there is
now experimental evidence for the correctness of a detailed theory on how this system could have started.
Thus Behe's thesis is very vulnerable to attack from an empirical quarter. A person who is committed to the belief that ID has occurred can brush aside such criticisms as that gene duplication provides
the complexity, that evolution can create systems from genes that are already around for other purposes, that some steps of evolution are no longer seen but were there before a system looked irreducibly
complex, or that some seemingly complex systems initially worked at a simpler level which eventually evolved to a complex level. However, when those criticisms are brushed aside the overall credibility of
the basic thesis is reduced.
Behe's thesis is also vulnerable to criticism on philosophical grounds. Behe makes a point of saying nothing about how or at what time an IC system is designed, but it is very unsatisfactory to stop an
enquiry at this point. It is pertinent to ask such questions as: Was there more than one design process? If not, was the design executed solely at the origin of life? If there was more than one design
process, how were the various processes coordinated? To what extent was the design carried out by natural processes? Can a non-Darwinian natural process account for the design itself? According to Behe,
IC must be determined on a case-by-case basis. Korthof10 has pointed out that this means that Design Theory is a hybrid theory at least some organisms are products of both design and evolution by
natural processes. Miller11 has taken this argument a step further. He says that if the ID theorists are right, then we should apply the explanation of design to every event in the natural history of the
planet. It is not logically tenable to allow that evolution could have produced some species but not others; therefore, the explanation of design must be invoked for the origin of every species, and that
was what biologists used to do, until it became impossible to take that seriously. Miller's book contains a chapter in which he gives several counter examples which refute Behe's claim that evolution
cannot produce complex, well-designed biochemical systems. Further, he shows that the biochemical machines whose origins Behe finds so mysterious actually provide powerful and compelling examples of
evolution in action.
Dembski12 in his most recent book has commented on the objection that "Design substitutes extraordinary explanations where ordinary explanations will do and thereby commits a god-of-the-gaps fallacy." At
the end of a lengthy attempt at rebuttal, he gets around to asking the important question, "How long are we to continue a search [for an explanation in terms of natural causes] before we have a right to
give up the search and declare not only that continuing the search is vain but also that the very object of the search is nonexistent?" He acknowledges that there is no precise line of demarcation. To my
mind this is a reason why the search should never be terminated.
5. Michael J. Behe, Darwin's Black Box: The Biochemical Challenge to Evolution (Touchstone, New York, 1996)
6. D. C. Lindsay, Review of Darwin's Black Box found on 29-09-00 at www.cs.colorado.edu/~Lindsay/creation/behe.html
7. H. J. Muller, Reversability in evolution considered from the standpoint of genetics, Biological Reviews 14 (1939), 261-280
8. N. Shanks and K. H. Joplin, "Redundant complexity: a critical analysis of intelligent design in biochemistry,'"Philosophy of Science 66 (1999), 268-298
9. M. J. Behe, "Self-organization and irreducible complex systems: A reply to Shanks and Joplin," Philosophy of Science 67 (2000), 155-162
10. Gert Korthof, "Does irreducible complexity refute neo-Darwinism? Darwin's Black Box, a review," 6 August 2000, online at home.wxs.nl/~gkorthof/korthof8.htm
11. Kenneth R. Miller, Finding Darwin's God: A Scientist's Search for Common Ground Bewteen God and Evolution (Cliff Street Books/ Harper Collins, New York, 1999)
12. William A. Dembski, Intelligent Design: The Bridge Between Science and Theology (InterVarsity Press, Downers Grove, IL, 1999)