irreducible complexity does not imply intelligent design
Posted August 24, 2005
Michael Behe's book Darwin's
Black Box is one of the most popular and extensively reviewed books promoting
intelligent design "theory." The concept of "irreducible complexity"
propagandized in that book has been touted by Behe and other intelligent design
advocates as a great discovery and used as one of the main tools in their
efforts to "destroy Darwinism" (the goal openly announced by such "leading lights"
of intelligent design as Phillip Johnson  and Jonathan Wells ).
complexity, according to "design theorists," implies intelligent design of
biological system. In fact, such a conclusion lacks a logical foundation. Irreducible
complexity even can more reasonably be construed as an argument against
Michael Behe's concept of irreducible
complexity (IC) (Behe 1996) has been critically discussed by experts in biology
-- see, for example, publications by H. Allen Orr (1997), Russell F. Doolittle
(1997), David Ussery (1999, 2004), Kenneth R. Miller (1999), Gert Korthof
(1999), Matt Inlay (2002), Pete Dunkelberg (2003), and others. The attitude of many
professional biologists to Behe's IC concept has even found its most
uncompromising expression in Kenneth Miller's words: "... the notion of
irreducible complexity is nonsense." (1999, p. 150).
the critical analysis of the IC concept by professional biologists seems to be
sufficient to dismiss Behe's alleged great discovery in biology, there is
another aspect to IC which, to my mind, makes the very notion of "IC implies
intelligent design (ID)" implausible.
concept identical in all but name to Behe's irreducible complexity was around
for a long time before Behe. It was applied to the problems of evolution of
various anatomical structures, such as the mammalian eye (recall the many times
answered question, "what good is half an eye?"), or the snakes' apparatus of
venom injection (Marcell 1976), etc.
relevant, a practically identical concept ("interlocking complexity") was
discussed from the standpoint of genetics already nearly 80 years earlier
(Muller 1918, 1939). Even the application of the IC concept to the molecular
assemblies within a biological cell (which is Behe's playing field) was put into
circulation some ten years before Behe (Cairns-Smith 1986). Unlike Behe and his
supporters, these Behe's predecessors did not claim that the concept in
question constitutes a great discovery or implies intelligent design, so in the
rendition of these predecessors it would hardly invoke Miller's categorical
rejection quoted above.
critical discussion of Behe's ideas has mainly concentrated on three aspects of
IC, to wit:
- The first
aspect of IC subjected to discussion has been about the very definition of IC.
To my knowledge, Behe himself has never acknowledged that his definition was in
any way imperfect. However, Behe's colleague William Dembski (viewed by the ID
advocates as their leading logician) admitted that Behe's idea of IC was "neither
exactly correct nor wrong" (Dembski 2002, p. 280).
- The second
aspect of IC subjected to critique was the question of whether molecular
systems offered by Behe as examples of IC are indeed IC. A number of biologists
pointed out that systems such as bacterial cilia or blood-clotting cascade
which, according to Behe, exemplify IC, are in fact reducible without losing
their "basic function." (See, for example, Miller 1999).
- The third
aspect of IC subjected to critique is the most important. Behe asserts that IC
systems (exemplified by the protein assemblies in biological cells) cannot have
evolved via a direct "Darwinian" path because such a path necessarily goes
through a sequence of intermediates each performing the same "basic" function. Since
any system comprising fewer parts than the IC system in question is, by
definition of IC, dysfunctional, it could not be an evolutionary precursor of
an IC system, or so says Behe.
Regarding evolution of IC system via an indirect evolutionary
path, Behe admits that such a process is possible but, in his opinion, so highly
improbable that it cannot be considered a feasible option.
The last point has been disputed by
professional biologists. They suggested detailed scenarios showing how, for
example, a bacterial flagellum could have evolved from evolutionary precursors
with a sufficiently high likelihood (Matzke 2003, Ussery 2004, Musgrave 2004).
The consensus of the majority of
professional biologists seems to favor the views of Behe's opponents. Except for vague protestations wherein Behe
and his supporters demand from their opponents highly detailed proofs of the
factual occurrence of indirect evolutionary paths leading to IC systems, Behe seems
to be unable to offer substantive counter-arguments.
In this essay I will analyze the IC
concept from a viewpoint different from the three aspects of the problem listed
above. I intend to show that even if the IC concept is valid, and even if many
biological systems are indeed IC, this in itself does not logically lead to
design inference. My contention is that IC in itself can more reasonably be construed
as an argument against design inference.
an essay titled "Irreducible Contradiction" posted to the internet in 1999 (see
reference) I suggested critical comments to Behe's Darwin's Black Box. This
essay was translated and printed in Russia (Perakh 2001a) and in Israel (Perakh
2001b). After its appearance in Russian
in Kontinent the essay was reproduced on several Russian websites and
invoked a discussion which sporadically continues even now (February 2005). By
the end of 2003 my book Unintelligent Design was published wherein
chapter 2 was essentially a slightly modified version of the same essay (Perakh
2004). Recently that chapter was
translated into Polish and appeared in the Polish journal Filozoficzne Aspekty Genezy (Philosophical Aspects of Origin) -- see http://www.nauka-a-religia.uz.zgora.pl/index.php?action=tekst&id=45
the nearly six years since the appearance on the internet of the essay in
question, Michael Behe has never uttered a word acknowledging the existence of
my critical remarks. Nor has William
Dembski, who has actively promoted Behe's irreducible complexity concept, ever
mentioned my critical comments. Neither did anybody else from the intelligent
Dembski posted an article titled "Irreducible Complexity Revisited," (Dembski
2005) which has initiated some discussion (RBH 2005, Perakh 2005). An article
by Behe appeared recently in New York Times, wherein Behe repeats again
the same much critiqued notions without having changed his position or having
accounted for a single point suggested by his critics. I think therefore it is
worthwhile to revisit certain points which seem to be in need of clarification,
regarding the IC concept and its alleged logical segueing into ID.
not discuss here Dembski's recent modifications of the IC definition (addressed
in Perakh 2005 and RBH 2005). Instead,
I will refer to Behe's original definition of IC, which, albeit suffering from certain
deficiencies (as admitted by Dembski 2002), does essentially reflect his
essence of Behe's original IC concept is as follows:
system is IC if:
It consists of several parts.
The parts are "well matched." (Behe offered no definition of the notion of
It performs a certain "basic" function (for example, clots blood);
It ceases to function if even a single part is missing.
discussed several examples of protein "machines" in biological cells, which,
according to Behe, are IC, Behe then asserts that the existence of IC systems
in a biological cell points to them being designed rather than having emerged
as a result of evolution. I intend to show that Behe's assertion contradicts logic.
that Behe's concept of IC comprises two components: one is complexity
and the other is irreducibility.
expends a lot of effort to demonstrate how staggeringly complex the protein
systems in a cell are. It is evident
that for Behe the complexity in question is part of his idea, pointing to
design as the alternative to evolution. According to Behe, biological systems
must have been designed because they (A) are very complex; and (B) cannot
function unless all of their parts are present.
(A) -- complexity -- note that Behe has not provided a definition of complexity. Several
such definitions have been suggested, though, by Dembski.
has been pointed out before (Perakh 2004), Dembski's various definitions of
complexity are often incompatible with each other. There is among them, though, a definition repeated by Dembski
many times, which is in tune with Behe's point (A). According to that definition
complexity is equivalent to small probability (Dembski 1998). For example,
Dembski asserts in his book that "probability measures are disguised complexity
measures" (page 114). Variations of this assertion are scattered over Dembski's
books. Thus the more complex a system, the less probable its spontaneous
emergence as a result of chance, or so says Dembski. So, according to Behe and
Dembski, the more complex a system, the more likely it was designed -- this is
the essence of point (A) in Behe's concept.
(B) -- irreducibility -- in Behe's concept asserts that an IC system loses its
function if even a single part is missing.
to Behe, protein "machines" in a cell meet both requirements for being IC --
they are very complex and they are irreducible.
goal now is to discuss: what if this assertion is true? Does it lead logically
to the design inference? Behe's answer
to this question is "Yes."
submit that Behe's answer is illogical. Here is why.
As I have argued before (Perakh
2004), contrary to Dembski's persistent assertions, complexity is certainly not
just disguised improbability. Examples to the contrary abound. Imagine a pile
of stones. Each stone has some irregular shape that resulted from a series of
chance events. Among these irregularly shaped stones we find a perfectly
rectangular brick. It has a simple
shape which can be described by a short (i.e. simple) program containing only
three numbers -- width, length, and height. On the other hand each of the
irregularly shaped stones can be described only by a more complex program containing
many numbers. However, the probability
of a rectangular brick being a result of chance is low: the brick is reasonably
(with a high probability) assumed to be a product of design. For irregularly
shaped stones the opposite is true -- the probability of their origin in chance
is larger than in design. Here the relationship between probability and
complexity is opposite that prescribed by Dembski's definition (but compatible
with the definition of Kolmogorov complexity -- see, for example, Chaitin 2003).
In this example simplicity rather
than complexity is a marker of design. I submit that the described example shows
not only that Dembski's definition of complexity fails for certain situations
but also that, generally, a more reasonable statement is that simplicity points
to design while complexity as such points to chance (more about this in
If this is so, then the first part
of Behe's IC concept -- complexity - is more reasonably construed as an
indication of "blind" evolution rather than of design.
Now turn to the second part of
Behe's IC -- irreducibility. Recall that Behe's idea is that losing a single
part of a protein "machine" makes it non-operational. Therefore, says Behe,
such a "machine" could not have evolved via a "Darwinian" evolutionary process
which requires the existence of functional precursors.
The simple fact is, though, that if
an IC system has been designed, we have a case of a bad design. If the loss of a single part destroys the
system's function, such a system is unreliable and therefore, if it is
designed, the designer is inept. When engineers design machines, bridges, skyscrapers,
TV sets, or artificial kidneys, they always try to envision what can go wrong
with their design and how to ensure that small defects do not result in a failure
of their product; to this end they build in certain redundancies so that in
case some part of the construction fails, its function will not be completely
lost but rather taken over by certain self-compensatory features.
IC systems, by definition, are
highly vulnerable to accidental damage.
IC systems, if they are designed,
are poorly designed.
It must be stressed that in this
case we go beyond the problem of suboptimal design. When we deal just with
suboptimal design as such, the ID advocates suggest various arguments
supposedly justifying the reasons for design being not optimal. For example,
one such argument is that we simply don't know anything about the designer's
reasons to behave as he does; hence our notion is just an argument from
ignorance; perhaps whatever from human limited standpoint looks like suboptimal
design has good reasons beyond our comprehension to be as it is, etc. Such an argument usually (albeit not always
explicitly) presumes that suboptimality is a "side effect" rather than a
deliberately chosen goal of the designer.
Whether such arguments are
convincing depends on the mindset of the particular persons. For this discourse, however, such an
argument is not really relevant. Indeed, Behe's concept contains as a crucial
part the assumption that the irreducibility of biological system is a marker of
design. Such an assumption is obviously
not about a designer who has failed to provide an optimal solution or
compromised in his design for some unknown reason. It is no longer about some "side
effect" which the designer has simply failed to correct or has kept for unknown
reasons, extraneous to the design's purpose.
Behe's concept assumes that the very
feature which makes the design bad means the system has been designed. In
other words, Behe's concept means that suboptimality is viewed not as just an unfortunate oversight
by the designer; nor is it viewed as something that, albeit seemingly
detrimental for the designed entity, has some reasons known only to the
designer but unfathomable to us. No, in Behe's concept the very suboptimality
is suggested as a marker of design: an IC system by definition is easily
destroyed by damaging just a single part, so a system's being IC means that its
vulnerability is its ineliminable feature.
Behe's idea implies that the system is IC (and hence suboptimal) because
such was the goal of the designer. "The
system is suboptimal, therefore it is a product of design" -- that is
what Behe's concept entails.
ID advocates are welcome to accuse
me of offering a caricature of their idea, but it cannot be helped when a
concept's essence sounds like a caricature or a parody; the idea that "IC implies
ID" can most succinctly be rendered by a maxim: stupid, therefore
If this is a satisfying logic, I
don't know what a lack of logic is.
Remember also that Behe's design
inference is based not on some positive evidence but rather on a negative
assertion: IC systems could not have
evolved via a "Darwinian" path. Since such a path is impossible, concludes
Behe, the only remaining option is design.
This is an argument of the "either-or"
type. I will not discuss here whether
or not there indeed are only two mutually-exclusive options. My point is
different: if Behe infers design only because the direct evolutionary path, in
his view, is impossible and an indirect evolutionary path is improbable,
then, to be consistent, he should use the same probabilistic criteria for
judging whether or not it is reasonable to assume that the feature which makes
design bad is a marker of design. How
probable is it that the putative designer deliberately designs his products to
be IC if this means the product will be unreliable?
Dembski asserts that ID does not
imply a smart designer (Dembski 2001). Designer can even be stupid, says
Dembski. However, from many other
utterances of ID advocates, including Dembski, it is clear that all such
statements are just a smoke screen and in fact they believe that their
"designer" is the God of the Bible. (See, for example, Dembski 1999, part 3, or
Johnson 2000.) This designer is supposed to be omnipotent and omni-benevolent.
In fact, ID advocates want to have their
cake and to eat it too. On the one hand they concede that the putative designer
may even be stupid -- this they say when trying to explain suboptimality of
design. On the other hand they speak
about Christian values, cultural war, the Logos of John's gospel and the
imminent triumph of ID over "materialistic" science. (Dembski 1999, part 3;
Johnson 2000). It is not by accident that the leading young earth creationist,
Henry Morris, who is more consistent in his frank biblical literalism, referred
to Dembski's contortions regarding the nature of the designer as "nonsense." (Morris
How probable is that the very
features that make design bad are markers of design (as follows from Behe's discourse)?
It is hardly less improbable than the evolution of protein assemblies via
indirect "Darwinian" paths.
If Behe infers design just because
evolution of protein assemblies via indirect "Darwinian" paths looks improbable
to him, design inference also has to be excluded because of the improbability
of the putative designer's deliberately incorporating in the protein assemblies
the very features (like IC) which make the design bad.
The above discourse is, to my mind,
sufficient to reject the design inference based on the IC concept, as logically
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In this essay I stated that to my knowledge Behe has never admitted that his original definition of IC (as rendered in his book of 1996) was in any way deficient. This statement was in error. In an article which can be seen at http://www.arn.org/docs/behe/mb_indefenseofbloodclottingcascade.htm, dated July 31, 2000, Behe pointed out that his original definition of 1996 had certain shortcomings and suggested another version of a definition of IC. In this version of 2000, Behe introduced a concept of various degrees of irreducible complexity and suggested that IC is determined by the number of unselected mutations in the system's predecessors. I apologize for the error. From the standpoint of this essay, however, this error is of no consequence: my thesis is not dependent on the definition of IC as it deals with the logical seguing of IC to ID and presumes that Behe's idea of IC itself is justified regardless of which version of a definition of IC is referred to. It may be worthwhile to point out that in the highly acclaimed by ID advocates Dembski's book No Free Lunch, published in 2002, where Dembski stated that Behe's original definiton was "neither exactly correct nor wrong," Dembski did not even mention Behe's version of the definition of IC of July 2000, and only suggested convoluted modifications of Behe's original definition of 1996. Apparently, the version of 2000 has not replaced the definition of 1996 in the minds of ID advocates. It certainly made even less of an impression on ID critics.