Icons of ID: Explanatory filter and false positives

The first Icon I will explore is the Icon of the Explanatory Filter being reliable, or in the words of Dembski “No false positives”.

Dembski’s opinion on “false positives” seems to have evolved over time. From an initial claim of reliability and “no false positives” via an admission that if the filter erroneously attributes design, it is useless to acceptance of “false positives”, the “Explanatory Filter” evolved from reliable to useless.

Despite the fact that “false positives” are inevitable and thus the filter is not only unreliable but in fact useless, Dembski and the ID movement seems to continue to insist that the Explanatory Filter is a reliable theoretical foundation for detecting design.

One may speculate as to the reasons why the ID movement is slow or reluctant to self correct. Is it due to a lack of peer review? Lack of peer review in the ID movement is self evident as its arguments are presented in books rather than in the more common format of papers to a scientific journal.

Is it because of the often strong belief that intelligent design must be the correct answer thus any design inference has to be reliable which seems to me to be a circular argument ?

I am not sure I have all the answers but I am hoping to take the reader on an interesting journey through the history of the “Explanatory Filter” from its conception to its early retirement.

The original claim was that:


I argue that the explanatory filter is a reliable criterion for detecting design. Alternatively, I argue that the Explanatory Filter successfully avoids false positives. Thus whenever the Explanatory Filter attributes design, it does so correctly.


Dembski bases his claim of “no false positives” on two weak arguments. The first argument is an inductive argument that states that whenever the filter has been applied and infered design, it did so correctly.


Dembski wrote:

“straightforward inductive argument: in every instance where the explanatory filter attributes design and where the underlying causal history is known, it turns out design is present; therefore design actually is present whenever the explanatory filter attributes design.”

W.A. Dembski, ed., Mere Creation, InterVarsity Press, 1998. p. 107

As Perakh argues:

While Dembski devotes several pages to the elaboration of this assertion, he does not substantiate it by providing any record which would indeed show his filter’s impeccable reliability.

The second argument is that the explanatory filter mimicks how we recognize intelligent causation.

“The explanatory filter is a reliable criterion for detecting design because it coincides with how we recognize intelligent causation generally.”

Again Perakh shows what is wrong with this claim. In fact, I would argue the opposite is true. When recognizing intelligent causation in for instance archaeology, criminology, and ever SETI, we rely on motives, means, opportunities or in other words pathways.


Dembski strengthened the claim by stating that:

“On the other hand, if things end up in the net that are not designed, the criterion will be useless.”

Dembski, William, 1999. Intelligent Design: The Bridge Between Science & Theology. P 141.

In other words, if it can be shown that “false positives” are inevitable, then it has been shown that the criterion to infer design is useless. So let’s explore this possibility.


In Dembski’s own words:

Now it can happen that we may not know enough to determine all the relevant chance hypotheses. Alternatively, we might think we know the relevant chance hypotheses, but later discover that we missed a crucial one. In the one case a design inference could not even get going; in the other, it would be mistaken. But these are the risks of empirical inquiry, which of its nature is fallible. Worse by far is to impose as an a priori requirement that all gaps in our knowledge must ultimately be filled by non-intelligent causes.

Dembski, William, 2001. No Free Lunch, Rowman & Littlefield, p 123


I argue that we are justified asserting specified complexity (and therefore design) once we have eliminated all known material mechanisms. It means that some unknown mechanism might eventually pop up and overturn a given design inference. But it also means that we have prima facie evidence of design and that we are justified in holding to this claim in the absence of such mechanisms being found. I also note that there can be cases where all material mechanisms (known and unknown) can be precluded decisively.


In other words, unknown mechanisms may eventually pop up.

I would say that by itself is sufficient to take Dembski’s conclusion seriously namely:

“On the other hand, if things end up in the net that are not designed, the criterion will be useless.”

But let’s explore further. When discussing “false negatives” Dembski argues:

One difficulty is that intelligent causes can mimic undirected natural causes, thereby rendering their actions indistinguishable from such unintelligent causes.


But I argue that the same applies however for undirected natural causes that can mimic intelligent causes. Or in other words evolutionary processes such as natural selection. That processes such as natural selection and variation can be shown to increase the information in the genome has been shown by Schneider in “ev: Evolution of Biological Information” and Adami et al’s “Evolution of biological complexity”.

But it is not only Intelligent Design critics who have reached this conclusion,Del Ratzsch, in “Nature, Design and Science” shows how Dembski’s filter is not only limited in its usefulness but also how it is vulnerable to “false positives”.

But there are other problems such as with Detachability:

“Detachability must always be relativized to a subject’s background and knowledge”

Ric Muchaga concludes that detachability has become a liability.

And of course he is right: our clever code that produces a “false positive” is not detachable. But there is an obvious problem: the DNA code is not detachable either! Certainly Dembski cannot believe that a mathematician might have figured out that life on earth would be based on a code constructed of four protein bases arranged in the shape of a double helix. Wasn’t God free to create life based on six protein bases, or from some other arrangement altogether?

Dembski is caught in a dilemma. If he gives up the detachability criterion, there will be no end of “false positives.” If he doesn’t give up the detachability criterion, he has reduced biology to a purely mathematical, a priori discipline, and he has denied a fundamental doctrine of Christian theology–namely, that God was perfectly free to create in any way he saw fit.

Del Ratzsch also show what is problematic with tractability:

“The problem with the tractability criterion is that there is no substantive discrimination among the patterns produced. The lack becomes accutely evident and the tractability requirement clearly loses all bite when omniscience expands those patterns to the set of all possible patterns.”

Del Ratzsch reaches the inevitable conclusion:

“I do not wish to play down or denigrate what Dembski has done. There is much of value in the Design Inference. But I think that some aspects of even the limited task Dembski set for himself still remains to be tamed.” “That Dembski is not employing the robust, standard, agency-derived conception of design that most of his supporters and many of his critics have assumed seems clear.”

So typically, patterns that are likely candidates for design are first identified as such by some unspecified (“mysterious”) means, then with the pattern in hand S picks out side information identified (by unspecified means) as releavant to the particular pattern, then sees whether the pattern in question is among the various patterns that could have been constructed from that side information. What this means, of course, is that Dembski’s design inference will not be particularly useful either in initial recognition or identification of design

What I have reservations about, however, is the fact that designs produced by the deliberate setting of natural processes to produce them seem to escape the filter, and that means that all filter-relevant design theories become gap theories.


“In the present case, however, it seems to me that design theories are going to have to produce some positive results which are not easily assimilable by reigning theories. And it seems to me that to date design has not achieved that. “

We may take notice of Dembski’s insightful words

“We have done amazingly well in creating a cultural movement, but we must not exaggerate ID’s successes on the scientific front.”

William Dembski

And yet we are faced with exaggerations of ID’s scientific successes such as the reliability of the explanatory filter. In addition Wimsatt, in response to an advertisement for Dembski’s “No Free Lunch” asks Dembski to clarify his position.

Wimsatt on the evolutionary psychology Yahoo group objects to the Advertisement text for Dembski’s book “No Free Lunch”

the Hype wrote:

In No Free Lunch, William Dembski shows that blind natural processes, such as the Darwinian mechanism of natural selection and random variation, are incapable of generating biological structures like the bacterial flagellum.

The response by Wimsatt:

I could not in conscience fail to respond to the ad for Bill Dembski’s new book, ““No Free Lunch”, and to the general tenor of the political push generated either within or by others using the so-called “intelligent design theory”. This is not a theory, but a denial of one, and a denial whose character is widely misrepresented, at least in the press.

Unfortunately “popular” presentations of “Intelligent Design” have tended to give the impression that it rested solely on mathematical demonstrations. Anyone who could have succeeded in showing that natural selection is incapable of generating biological structures according to standards from mathematics or logic would have constructed a mathematical proof that would have dwarfed Godel’s famous Undecideability theorem in importance. As one who read Dembski’s original manuscript for his first book, found much to like in it, and had appreciative remarks on the dust jacket of the first printing, I can say categorically that Demski surely has shown no such thing, and i call upon him as a mathematician to deny and clarify the implications of this advertising copy.

My question: Has Dembski clarified these isssue?

Maybe Dembski should have taken notice of his own words

Critics and enemies are useful. The point is to use them effectively. In our case, this is remarkably easy to do. The reason is that our critics are so assured of themselves and of the rightness of their cause. As a result, they rush into print their latest pronouncements against intelligent design when more careful thought, or perhaps even silence, is called for.


Seems that Dembski should have stayed silent on the issue of the lack of usefulness of the explanatory filter and “false positives”. In fact, the reliability claim is but one example in which Dembski seems to have rushed to judgement in his pronouncements, other examples include the “No Free Lunch” advertisement claims and in a future posting I intend to explore Dembski’s use and abuse of the “No free lunch theorems” and his subsequent reversals when it was pointed out to him that his interpretation of these theorems “was written in jello”

One may wonder why Dembski has avoided to respond to these issues, since they undermine the most basic foundations of his claims. Perhaps the following statement can help us understand

I’m not going to give away all my secrets, but one thing I sometimes do is post on the web a chapter or section from a forthcoming book, let the critics descend, and then revise it so that what appears in book form preempts the critics’ objections. An additional advantage with this approach is that I can cite the website on which the objections appear, which typically gives me the last word in the exchange. And even if the critics choose to revise the objections on their website, books are far more permanent and influential than webpages.

I guess this may mean that we may have to wait for the next book from Bill before we may expect a coherent answer. But is it just me who finds Bill’s approach less than ‘scholarly’?