Until now, I've based my dismissal of Dembski's design argument on the
articles I've found on the web. I've read all of Dembski's non-theological
articles that I've been able to find, and several reviews of his book, "The
Design Inference". However, I wanted to read the book itself, and have it
had on request from the public library for many weeks. Now, at last, I've
received it and read it. (No, the wait wasn't because of it's
popularity--quite the opposite! The book is virtually unknown here in
Britain, and the library had to acquire it through the
inter-library loan system.)
I'd like to summarize my views on the book, and hopefully provoke some
discussion. (By the way, I studied statistics at university, to BSc level,
but that was a long, long time ago, so I would consider myself a
well-informed layman on the subject of statistics.)
The Law of Small Probability
Most of the book is devoted to establishing this law, which says--put
simply--that "specified events of small probability do not occur by chance".
It seems to me that this law introduces two novelties into statistical
(a) It allows a specification to be established retrospectively, i.e. after
the event in question has occurred.
(b) It provides a method for setting a small probability bound, below which
we can justifiably say that events do not occur.
Let me say that these are novelties as far as I'm concerned, but I can't say
with any confidence that they haven't already been addressed in the
Now, I don't propose to discuss the LSP in detail. Such a discussion would
be pretty technical and probably not of interest to many readers here. If
Dembski has succeeded in putting this law on a firm theoretical basis, then
I think he will have made a significant contribution to statistics. However,
I'm rather doubtful about whether he has done so. Several of his inferences
seem dubious to me. But I don't feel competent to make a definite
pronouncement on the matter. I'd like to wait and see what the statistics
community has to say on the matter. Does anyone here know what the reaction
of the statistics community has been?
Anyway, regardless of whether this law does indeed have a firm theoretical
foundation, I'm quite willing to accept it as a practical methodology. The
law *seems* reasonable, and it's one which we all intuitively apply. It's
our intuition of such a law that enables us to cry foul when we see someone
deal a perfect Bridge hand (each player receives 13 cards of one suit). It's
our intuition of such a law that leads us to conclude that Nicholas Caputo
rigged the ballots (in Dembski's favourite example).
Dembski wants to establish this law because he hopes to use it to to prove
that life could not occur by chance. Well, I have no problem with that.
Dawkins implicitly uses such a law when he argues, in The Blind Watchmaker,
that "We can accept a certain amount of luck in our explanations, but not
In developing his LSP, Dembski is doing science (or perhaps, more
accurately, mathematics). Whether it is good or bad science remains to be
seen (as far as I'm concerned). However, when he moves on from the LSP to
the Explanatory Filter, Dembski jumps from the arena of science into the
quagmire of pseudo-science.
The Explanatory Filter
Dembski's Explanatory Filter (EF) says that, once you've eliminated
regularity and chance as possible explanations of an event, you must
conclude that the event is the result of design. So what's wrong with this?
Well, first of all, Dembski is equivocal about what he means by "design". He
initially defines design to be the "set-theoretic complement of the
disjunction regularity-or-chance", or, in other words: "To attribute an
event to design is to say that it cannot reasonably referred to either
regularity or chance" (p. 36). By this definition, the EF is tautological,
but Dembski promises that he will later provide us with a means of
determining which cases of "design" can be attributed to "intelligent
agency". Or is he going to attribute *all* cases of design to intelligent
agency? This is where Dembski starts to equivocate.
i) On page 36, he writes: "The principal advantage of characterizing design
as the complement of regularity and chance is that it avoids committing
itself to a doctrine of intelligent agency. In practice, when we eliminate
regularity and chance, we typically do end up with an intelligent agent.
Thus, in practice, to infer design is typically to end up with a "designer"
in the classical sense." Dembski's use of the word "typically" strongly
imples that not all cases of design can be attributed to intelligent agency,
i.e. that design does not necessarily imply intelligent agency.
ii) In Section 2.4, "From Design to Agency" (starting p. 62), Dembski
returns to this issue and attempts to establish a connection between design
and (intelligent) agency. I'm not going to address the issue of whether he
succeeds in doing so. All I'm interested in for now is whether he claims to
establish a *necessary* connection, i.e. that *all* cases of design can be
attributed to agency. The answer is that he does. In the final paragraph of
the section, he summarizes: "It's now clear why the Explanatory Filter is so
well suited for recognizing intelligent agency: for the Explanatory Filter
to infer design coincides with how we recognize intelligent agency
generally." And again: "It follows that the filter formalizes what we have
been doing right along when we recognize intelligent agents. The Explanatory
Filter pinpoints how we recognize intelligent agency" (p. 66).
iii) In case anyone should try to reconcile the contradiction of (i) and
(ii) above by claiming that "typically" should be read as something like "to
all intents and purposes", let me point out that Dembski actually gives an
example of a situation where the EF (according to Dembski) indicates design
but we where we cannot (according to Dembski) infer an intelligent agency.
The example is on page 226, and I'll give details if anyone is interested.
But I think it's sufficient to note Dembski's conclusion: "Thus, even though
in practice inferring design is the first step in identifying an intelligent
agent, taken by itself design does not require that such an agent be
posited. The notion of design that emerges from the design inference must
not be confused with intelligent agency." (Note that the terms "design
inference" and "Explanatory Filter" appear to be synonyomous. One might have
assumed that DI = EF + the mysterious extra criterion that allows us to
distinguish between simple design and intelligent agency, but the last
sentence quoted shows that this cannot be the case.)
So despite, the claim to the contrary on page 66, it seems that the EF on
its own is not sufficient to identify intelligent agency. In that case, what
additional information is required? Dembski continues (p. 227): "When the
design inference infers design, its primary effect is to limit our
explanatory options. Only secondarily does it help identify a cause. To
investigate a cause we need to investigate the particulars of the situation
where design was inferred. Simply put, we need more details. In the Caputo
case, for instance, it seems clear enough what the causal story is, namely,
that Caputo cheated. In the probabilistically isomorphic case of Alice and
Bob, however, we may have to live without a causal explanation..." So, in
order to attribute the Caputo case to design, we need to know the causal
design story (he cheated). But the whole purpose of the design inference was
to give us a way of identifying design *without* knowing the causal story.
Dembski has just shot himself in the foot!
Having seen Dembski demolish the whole raison d'etre of his own EF, it
hardly seems worth discussing it any further. But I'd like to clear up
another point of confusion, namely the distinction between Dembski's
"regularity" and "chance" categories.
It seems rather confusing to use the name "regularity" in opposition to
"chance", since even chance events exhibit regularities. What is a
probability distribution if not a regularity? When we look further, we see
that the events Dembski assigns to the regularity category are those which
"will (almost) always happen". In other words, those with a high probability
(a probability of 1 or nearly 1). In fact, Dembski later refers to them as
"highly probable" (HP) events. Dembski also refers to chance events as
events of "intermediate probability" (IP). So why draw a distinction between
HP and IP events? After all, the boundary between them is undefined (Dembski
never gives a boundary probability), and both categories of events are going
to ultimately suffer the same fate (be dismissed as not due to design). I
can see no theoretical reason for distinguishing between them, only a
practical one: when considering the nature of a particular event, we can
rule out design immediately if its probability is sufficiently high--there's
no need to waste time worrying about whether it's specified or not. From a
logical point of view, however, we might just as well lump these two
categories together. And, if we do that, what should we call the new
category? Well, we could call it "regularity", since, as I've already said,
even chance events have regularities. But this seems to presuppose that the
remaining category (design) can't also exhibit regularities, which seems to
me like an unwarranted assumption. In fact, the only sensible name that I
can think of is "not designed"!
So, it seems that if the Explanatory Filter says anything at all, it amounts
to the following: once we've eliminated all the possible "not designed"
explanations, we must conclude that the event is due to design. In other
words, it's a tautology!
The Inflationary Fallacy
Although I said I wasn't going to discuss Dembski's Law of Small Probability
in detail, I'd like to address one issue related to it, not because it's an
important one, but just because it interests me.
In justifying his "universal probability bound", Dembski argues that he
doesn't need to allow for the probabilistic resources of the multiple
universes which, according to some physicists, result from inflationary
big-bang cosmology or quantum mechanics. He writes: "...there is something
deeply unsatisfying about positing these entities simply because chance
requires it" (p. 215). It's rather parochial of Dembski to assume that
physicists have proposed these theories just to undermine probabilistic
arguments of the sort he wants to make. I'm sure that's not the case. And,
if these other universes really do exist, then we must face up to the
While not accepting the possibility that such universes exist, Dembski
attempts to argue that, if they did, they would make the concept of chance
unintelligible: "But with unlimited probabilistic resources, we lose any
rational basis for eliminating chance". Leaving aside the question of
whether these multiple universe theories necessarily entail an *infinity* of
universes, this is an interesting point, and I think it betrays Dembski's
agenda. There would indeed, no longer be any rational basis for rejecting a
chance explanation of the origin of intelligent life (Dembski's aim). No
matter how infinitesimally small the probability of life might be, it would
occur in an infinitesimal proportion of universes, and we wouldn't be
surprised to find ourselves in such a universe, because, we couldn't
possibly find ourselves in any of the others.
However, the same argument does not apply when we consider other chance
events which are not vital to our very existence. To take Dembski's example:
"Despite a life of unremitting charity and self-sacrifice, did Mother Teresa
in her last days experience a neurological accident that caused her to
become an ax murderer?" Well, if we assume that such an event had
infinitesimal but non-zero probability, then, yes, there will be universes
where that happened. But there's no particular reason why we should find
ourselves in one of those universes. Therefore we have every right to be
surprised, nay astounded, if our own Mother Theresa was revealed to be an ax
murderer, and to reject the chance hypothesis. It follows that there will be
some *some* universes in which the chance hypothesis will be wrongly
rejected, but the probability of that happening in *our* universe is
In short, I think Dembski is wrong to exclude multiple universes in
principle. However, I for one would also find it deeply unsatisfying if the
naturalistic explanation for life had to resort to multiple universes,
unless the arguments for those multiple universes were unimpeachable (of
which I'm yet to be convinced).
Is There Design in Nature?
Interestingly, Dembski doesn't address this question in TDI, although it's
clear that that's what the book is leading up to, and some of his supporters
claim that it does indeed do so. For example, in "Scientists Find Evidence
of God" (http://www.arn.org/docs/insight499.htm) by Stephen Goode we find:
"Dembski recently published his own addition to the ever-growing Intelligent
Design Movement, a closely argued book that he calls The Design Inference,
in which Dembski (whose impressive list of degrees led one friend to
describe him as "the perpetual student") brings to bear his knowledge of
symbolic logic and mathematics to argue in favor of design in nature."
I suspect that many rank-and-file creationists are laying out their
hard-earned cash for this book in the expectation of finding an argument for
ID in nature. If so, they're wasting their money, because what they're
actually getting is mostly a technical treatise on statistics, which, valid
or not, is going to be of interest to very few people. By the way, here in
Britain the book costs £40, about 4 times the cost of a typical popular
science book. That's quite a lot of money to waste if it isn't what you
Anyway, given that Dembski doesn't attempt to apply the Explanatory Filter
to nature in this book, does he do it anywhere else? Well, I haven't been
able to find an application of the Explanatory Filter as such, but I've
found some on-line articles in which Dembski uses some related concepts
named "actual specified complexity" and "complex specified information"
(CSI). As far as I can tell, these two terms are synonymous with each other,
and a phenomenon is considered to possess these attributes if it results
from a specified event of small probability.
So what does Dembski say about actual specified complexity? Well, nothing
"Does nature exhibit actual specified complexity? This is the million dollar
question. Michael Behe's notion of irreducible complexity is purported to
be a case of actual specified complexity and to be exhibited in real
biochemical systems (cf. his book Darwin's Black Box). If such systems are,
as Behe claims, highly improbable and thus genuinely complex with respect
to the Darwinian mechanism of mutation and natural selection and if they
are specified in virtue of their highly specific function (Behe looks to
such systems as the bacterial flagellum), then a door is reopened for
design in science that has been closed for well over a century. Does nature
exhibit actual specified complexity? The jury is still out." Explaining
Unfortunately, it seems that some of Dembski's followers haven't heard that
the jury is still out:
"Drawing upon design-detection techniques in such diverse fields as forensic
science, artificial intelligence, cryptography, SETI, intellectual property
law, random number generation, and so forth, William Dembski argues that
specified complexity is a sufficient condition of inferring design and that,
moreover, such specified complexity is evident in nature." William Lane
Just one more point. Dembski use specified complexity as a measure of
improbability. But, as he himself says: "...probabilities are always
assigned in relation to chance hypotheses". So it's misleading to refer to
specified complexity as a singular measure. A phenomenon has a separate
measure of specified complexity for each of the possible chance hypotheses
that could explain it.
Well, that will do for now. Comments would be welcomed!
Richard Wein (Tich)
"The most formidable weapon against errors of every kind is reason. I have
never used any other, and I trust I never shall." -- Thomas Paine, "Age of
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