From Natural History, April, 2002, page 76
Detecting Design in the Natural Sciences
William A. Dembski
Intelligence leaves behind a characteristic signature.
(replied to by Mystery Science Theatre by Robert T. Pennock)
In ordinary life, explanations that invoke chance, necessity, or design cover every eventuality. Nevertheless, in the natural sciences one of these modes of explanation is considered superfluous—namely, design. From the perspective of the natural sciences, design, as the action of an intelligent agent, is not a fundamental creative force in nature. Rather, blind natural causes, characterized by chance and necessity and ruled by unbroken laws, are thought sufficient to do all nature's creating. Darwin's theory is a case in point.
But how do we know that nature requires no help from a designing intelligence? Certainly, in special sciences ranging from forensics to archaeology to SETI (the Search for Extraterrestrial Intelligence), appeal to a designing intelligence is indispensable. What's more, within these sciences there are well-developed techniques for identifying intelligence. Essential to all these techniques is the ability to eliminate chance and necessity.
For instance, how do the radio astronomers in Contact (the Jodie Foster movie based on Carl Sagan's novel of the same name) infer the presence of extraterrestrial intelligence in the beeps and pauses they monitor from space? The researchers run signals through computers that are programmed to recognize many preset patterns. Signals that do not match any of the patterns pass through the "sieve" and are classified as random. After years of receiving apparently meaningless "random" signals, the researchers discover a pattern of beats and pauses that corresponds to the sequence of all the prime numbers between 2 and 101. (Prime numbers, of course, are those that are divisible only by themselves and by one.) When a sequence begins with 2 beats, then a pause, 3 beats, then a pause . . . and continues all the way to 101 beats, the researchers must infer the presence of an extraterrestrial intelligence.
Here's why. There's nothing in the laws of physics that requires radio signals to take one form or another. The sequence is therefore contingent rather than necessary. Also, it is a long sequence and therefore complex. Note that if the sequence lacked complexity, it could easily have happened by chance. Finally, it was not just complex but also exhibited an independently given pattern or specification (it was not just any old sequence of numbersbut a mathematically significant one—the prime numbers).
Intelligence leaves behind a characteristic trademark or signature—what I call "specified complexity." An event exhibits specified complexity if it is contingent and therefore not necessary; if it is complex and therefore not easily repeatable by chance; and if it is specified in the sense of exhibiting an independently given pattern. Note that complexity in the sense of improbability is not sufficient to eliminate chance: flip a coin long enough, and you'll witness a highly complex or improbable event. Even so, you'll have no reasonnot to attribute it to chance.
The important thing about specifications is that they be objectively given and not just imposed on events after the fact. For instance, if an archer shoots arrows into a wall and we then paint bull's-eyes around them, we impose a pattern after the fact. On the other hand, if the targets are set up in advance ("specified") and then the archer hits them accurately, we know it was by design.
In my book The Design Inference, I argue that specified complexity reliably detects design. In that book, however, I focus largely on examples from the human rather than the natural sciences. The main criticism of that work to date concerns whether the Darwinian mechanism of natural selection and random variation is not in fact fully capable of generating specified complexity. More recently, in No Free Lunch, I show that undirected natural processes like the Darwinian mechanism are incapable of generating the specified complexity that exists in biological organisms. It follows that chance and necessity are insufficient for the natural sciences and that the natural sciences need to leave room for design.
William A. Dembski, who holds Ph.D.'s in mathematics and philosophy, is an associate research professor at Baylor University and a senior fellow with the Discovery Institute in Seattle. His books include The Design Inference: Eliminating Chance Through Small Probabilities (Cambridge University Press, 1998) and No Free Lunch: Why Specified Complexity Cannot Be Purchased Without Intelligence (Rowman and Littlefield, 2001).
Special Report: Intelligent Design?
The Challenge of Irreducible Complexity by Michael J. Behe
The Flaw in the Mousetrap by Kenneth R. Miller
Detecting Design in the Natural Sciences by William A. Dembski
Mystery Science Theatre by Robert T. Pennock
Elusive Icons of Evolution by Jonathan Wells