Chance, Necessity, and the War against Science

Review of The Design Inference: Eliminating Chance Through Small Probabilities.
William A. Dembski. Cambridge University Press, Cambridge, UK, 1998. 272 pp.

Massimo Pigliucci
(Published in BioScience 50(1):79-81, 2000)

To a superficial observer, so wonderful a regularity may be admired as the effect of either chance or design; but a skillful algebraist immediately concludes it to be the work of necessity. (David Hume)

Here we go again. More than 200 years after Hume's (1779) devastating critique of the argument from design, somebody else is trying to mathematically demonstrate the impossibility of natural explanations for the order of the universe, and of biological evolution in particular. To be sure, William A. Dembski's book explicitly talks about evolution in only one section spanning a mere seven pages, and quoting only one evolutionist, Richard Dawkins. However, the book has been hailed (e.g., in the endorsements assembled here) as a revolutionary contribution to design theory (the latest incarnation of "creation science"). Furthermore, it is soon to be followed by a more explicit attack by Dembski on evolution, Uncommon Descent, which "seeks to reestablish the legitimacy and fruitfulness of design within biology" (click here).

What is the "design inference," and why, as evolutionists and scientists, should we care about the concept? The answer to the first question: a mix of trivial probability theory and nonsensical inferences. The answer to the second one: this book is part of a large, well-planned movement whose objective, I contend, is nothing less than the destruction of modern science and its substitution with a religious system of belief. Let me briefly explain both claims.

The basic tenet of Dembski's book is that there are three possible explanations for any observed set of events: regularity, chance, and design. Regularity describes such phenomena as  the rising and setting of the sun. Chance is most simply exemplified by the outcomes of tossing a fair coin. Design can be found--according to Dembski--in biological evolution, cryptography, plagiarism, and the suspicious doings of one Democratic election commissioner in New Jersey named Nicholas Caputo (more on him later). Dembski then proposes what he calls an "explanatory filter" to determine which explanation correctly accounts for any particular phenomenon. The filter works by successive exclusion: if something is not a "regular" natural phenomenon, it may be chance or design. If it is not the former, it must be the latter. This kind of reasoning is, of course, quite trivial, and it was worked out in probability theory well before the appearance of this book. As Dembski himself acknowledges, the statistician Andrei Kolmogorov had all the pieces of the puzzle in place by 1965.

But never mind that. If Dembski had simply defined "design" as what in biology is known as "necessity" (Monod 1971), his book would have reduced to another case of somebody reinventing the wheel. Instead, he goes much further, asserting that "in practice, to infer design is not simply to eliminate regularity and chance, but to detect the activity of an intelligent agent" (p. 62). This claim is what turns his opus from triviality to nonsense.

Although Dembski cloaks his logic with semi-obscure (and totally useless in practice) pseudo-mathematical jargon and symbolism, the essence of his argument is easy to understand. It is best exemplified by his own treatment of the above-mentioned New Jersey election commissioner. Nicholas Caputo, nicknamed "the man with the golden arm," was charged with electoral fraud because in 41 elections he oversaw, 40 had seen the Democrats at the top of the ballot and only one had the Republicans placed first. The probability of this occurring by chance in the random drawings that Caputo claimed to have conducted is less than one in 50 billion. Regardless of the odds, however, the New Jersey Supreme Court did not convict Caputo because, after all, even very unlikely events can occur by chance. In the absence of additional evidence, the Court simply ordered Caputo to change the way in which the drawings were conducted to avoid "further loss of public confidence in the integrity of the electoral process." (Who says that jurists have no sense of humor?)

Dembski--as would anyone else with a bit of common sense and an elementary understanding of probability theory--concludes that the Court indeed had enough evidence to convict. Why? Because additional information available at the time--that is, that there is an advantage in being first on a ballot and that Caputo was a Democrat--clearly pointed to design, not chance. In other words, chance can be discarded as a reasonable alternative if two conditions hold: the probability of an event is very small, and the information available about that event allows someone to specify a particular pattern in advance. To put it even more simply, the following sequences from flipping a coin, TTHTTHTHHT and HHHHHHHHHH, have exactly the same probability of occurrence. However, your suspicion that the first one is genuinely random, whereas I created the second by simply typing the letters on a keyboard, would indeed be correct.

An important component of Dembski's argument is what he calls "probabilistic resources." Because the design inference is established on two pillars--the occurrence of a specifiable ("detachable," in the author's jargon) pattern and a small probability of occurrence--Dembski is faced with the problem of how small such a probability actually has to be before chance can be ruled out. Instead of relying on the commonly understood limitation of statistical theory, which recognizes that any probability level is arbitrary and, therefore, that answers in science are only tentative and always subject to revision, Dembski wants more, much more. He submits that there is an absolute probability level that can be used as a universal yardstick for inferring design: 1/2 x 10-150. How did he get there? By estimating that there are 1080 particles in the universe, that no transition between physical states is possible at a rate faster than 10-45 seconds (the well-known Planck time), and that the universe is not likely to exist for a total of more than 1025 years. 1080 x 1045 x 1025 is indeed 10150. The 1/2 multiplier in front of the probability expression is to insure that our chances of reaching the correct conclusion are better than one in two (a rather arbitrary number in and of itself, of course). The basic idea here is powerful: if Dembski can demonstrate that the probability of a molecule of DNA forming in the primordial soup approaches what he calls this "universal small probability," then life did not evolve by chance.

Too bad he missed the solution to this riddle, which has been proposed several times during the last few centuries, most prominently (and in various fashions) by Hume (1779), Darwin (1859), and Jacques Monod (1971). According to these thinkers, if a given phenomenon occurs with low probability and also conforms to a pre-specified pattern, then there are two possible conclusions: intelligent design (this concept is synonymous with human intervention) or necessity, which can be caused by a nonrandom, deterministic force such as natural selection. Caputo's doing was the result of (fraudulent) human design; biological evolution is the result of random phenomena (mutation or recombination, among other processes) and deterministic phenomena (natural selection). It is disheartening to see how many people don't seem to be able to understand or accept this simple and beautiful conclusion.

More than disheartening is the background into which Dembski's book falls. In fact, I find it rather maddening. I will list a few pieces of additional information and then let the reader decide if I am justified in inferring a conspiracy behind this book. Dembski's book is endorsed on the back cover by two people from the same universities where he matriculated. The inside cover comes with a bold hail by David Berlinski, who represented the creationist side in a recent PBS debate on evolution versus creation. And Dembski's list of acknowledgments reads like a "Who's Who" of the neocreationist movement, including Michael Behe, Phillip Johnson, and Alvin Plantinga. According to the book, Dembski is "a Fellow of the Discovery Institute's Center for the Renewal of Science and Culture" (CRSC). A bit scarce as an academic reference, no? The reason may be that the Discovery Institute (www.discovery. org/crsc/index.html) is a conservative public policy think tank with the declared intent of promoting the intelligent design theory as "a scientific research program" that "has implications for culture, politics, and the humanities, just as materialist science has such implications." A document called "The Wedge," which has been associated with the CRSC, has recently been circulated on the Internet ( The Wedge amounts to a detailed plan for insinuating intelligent design and other creationist ideas in the public as well as the academic arenas, with the ultimate goal of overthrowing the current scientific establishment and establishing a theistic science. Dembski's book can be seen as part of one of the steps of the Wedge strategy.

Unfortunately, Cambridge University Press has offered a respectable platform for Dembski to mount his attack on "materialist science"--which, of course, includes evolution. My hope is that scientists will not dismiss this book as just another craze originating in the intellectual backwaters of America. Neocreationism should be a call to arms for the science community. The battle is already raging, and scientists and educators are still not sure if they should even bother paying attention.

References cited