1How Not to Detect Design*A review of William A. Dembski’s The Design Inference -- Eliminating Chance Through SmallProbabilities. Cambridge: Cambridge University Press. 1998. xvii + 243 pg. ISBN 0-521-62387-1.Branden Fitelson, Christopher Stephens, Elliott Sober†‡Department of Philosophy, University of Wisconsin, MadisonAs every philosopher knows, “the design argument” concludes that God exists frompremisses that cite the adaptive complexity of organisms or the lawfulness and orderliness of thewhole universe. Since 1859, it has formed the intellectual heart of creationist opposition to theDarwinian hypothesis that organisms evolved their adaptive features by the mindless process of natural selection. Although the design argument developed as a defense of theism, the logic ofthe argument in fact encompasses a larger set of issues. William Paley saw clearly that wesometimes have an excellent reason to postulate the existence of an intelligent designer. If wefind a watch on the heath, we reasonably infer that it was produced by an intelligent watchmaker. This design argument makes perfect sense. Why is it any different to claim that the eye wasproduced by an intelligent designer? Both critics and defenders of the design argument need tounderstand what the ground rules are for inferring that an intelligent designer is the unseen causeof an observed effect.Dembski’s book is an attempt to clarify these ground rules. He proposes a procedure fordetecting design and discusses how it applies to a number of mundane and nontheologicalexamples, which more or less resemble Paley’s watch. Although the book takes no stand onwhether creationism is more or less plausible than evolutionary theory, Dembski’s epistemologycan be evaluated without knowing how he thinks it bears on this highly charged topic. In whatfollows, we will show that Dembski’s account of design inference is deeply flawed. Sometimes heis too hard on hypotheses of intelligent design; at other times he is too lenient. Neithercreationists nor evolutionists nor people who are trying to detect design in nontheologicalcontexts should adopt Dembski’s framework.The Explanatory FilterDembski’s book provides a series of representations of how design inference works. Theexposition starts simple and grows increasingly complex. However, the basic pattern of analysiscan be summarized as follows. Dembski proposes an “explanatory filter” (37), which is aprocedure for deciding how best to explain an observation E:(1) There are three possible explanations of E -- Regularity, Chance, and Design. Theyare mutually exclusive and collectively exhaustive. The problem is to decide which ofthese explanations to accept.2(2) The Regularity hypothesis is more parsimonious than Chance, and Chance is moreparsimonious than Design. To evaluate these alternatives, begin with the mostparsimonious possibility and move down the list until you reach an explanation you canaccept.(3) If E has a high probability, you should accept Regularity; otherwise, reject Regularityand move down the list. (4) If the Chance hypothesis assigns E a sufficiently low probability and E is “specified,”then reject Chance and move down the list; otherwise, accept Chance.(5) If you have rejected Regularity and Chance, then you should accept Design as theexplanation of E.The entire book is an elaboration of the ideas that comprise the Explanatory Filter. Notice that1the filter is eliminativist, with the Design hypothesis occupying a special position.We have interpreted the Filter as sometimes recommending that you should acceptRegularity or Chance. This is supported, for example, by Dembski’s remark (38) that “if Ehappens to be an HP [a high probability] event, we stop and attribute E to a regularity.” However, some of the circumlocutions that Dembski uses suggest that he doesn't think youshould ever “accept” Regularity or Chance. The most you should do is “not reject” them. 2Under this alternative interpretation, Dembski is saying that if you fail to reject Regularity, youcan believe any of the three hypotheses, or remain agnostic about all three. And if you rejectRegularity, but fail to reject Chance, you can believe either Chance or Design, or remain agnosticabout them both. Only if you have rejected Regularity and Chance must you accept one of thethree, namely Design. Construed in this way, a person who believes that every event is the resultof Design has nothing to fear from the Explanatory Filter -- no evidence can ever dislodge thatopinion. This may be Dembski's view, but for the sake of charity, we have described the Filter interms of rejection and acceptance.The Caputo ExampleBefore discussing the filter in detail, we want to describe Dembski’s treatment of one ofthe main examples that he uses to motivate his analysis (9-19,162-166). This is the case ofNicholas Caputo, who was a member of the Democratic party in New Jersey. Caputo’s job was to determine whether Democrats or Republicans would be listed first on the ballot. The partylisted first in an election has an edge, and this was common knowledge in Caputo’s day. Caputohad this job for 41 years and he was supposed to do it fairly. Yet, in 40 out of 41 elections, helisted the Democrats first. Caputo claimed that each year he determined the order by drawingfrom an urn that gave Democrats and Republicans the same chance of winning. In spite of hisprotestations, Caputo was brought up on charges and the judges found against him. They3rejected his claim that the outcome was due to chance, and were persuaded that he had rigged theresults. The ordering of names on the ballots was due to Caputo’s intelligent design.In this story, the hypotheses of Chance and Intelligent Design are prominent. But what ofthe first alternative, that of Regularity? Dembski (11) says that this can be rejected because ourbackground knowledge tells us that Caputo probably didn’t innocently use a biased process. Forexample, we can rule out the possibility that Caputo, with the most honest of intentions, spun aroulette wheel in which 00 was labeled “Republican” and all the other numbers were labeled“Democrat.” Apparently, we know before we examine Caputo’s 41 decisions that there are justtwo possibilities -- he did the equivalent of tossing a fair coin (Chance) or he intentionally gavethe edge to his own party (Design).There is a straightforward reason
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