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Detecting Design in the Natural Sciences

By William A. Dembski
What emerges is a designed object, and the designer is successful to the degree that the object fulfills the designer's purpose. In the case of human designers, this four-part design process is uncontroversial. Baking a cake, driving a car, embezzling funds, and building a supercomputer each presuppose it. Not only do we repeatedly engage in this four-part design process, but we have witnessed other people engage in it countless times. Given a sufficiently detailed causal history, we are able to trace this process from start to finish.
Nevertheless, when it comes to living things, the biological community holds that a very different type of causal story is required. To be sure, the biological community admits that biological systems appear to be designed. For instance, Oxford biologist Richard Dawkins writes, "Biology is the study of complicated things that give the appearance of having been designed for a purpose." Likewise, Nobel laureate Francis Crick writes, "Biologists must constantly keep in mind that what they see was not designed, but rather evolved."
The term "design" is everywhere in the biological literature. Even so, its use is carefully regulated. According to the biological community, the appearance of design in biology is misleading. This is not to deny that biology is filled with marvelous contrivances. Biologists readily admit as much. Yet as far as the biological community is concerned, living things are not the result of the four-part design process described here.
But how does the biological community know that living things are only apparently and not actually designed? The exclusion of design from biology certainly contrasts with ordinary life where we require two primary modes of explanation: blind material forces on the one hand, intentional agency or design on the other. 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 material forces, characterized by chance and necessity and ruled by unbroken laws, are thought sufficient to do all nature's creating.
What has kept design outside the natural sciences since Darwin published his Origin of Species 140 years ago is the absence of precise methods for distinguishing intelligently caused objects from unintelligently caused ones. For design to be a fruitful scientific concept, scientists have to be sure that they can reliably determine whether something is designed. Johannes Kepler thought the craters on the moon were intelligently designed by moon dwellers. We now know that the craters were formed by blind natural forces.
It is this fear of falsely attributing something to design only to have it overturned later that has prevented design from entering the natural sciences. With precise methods for discriminating intelligently from unintelligently caused objects, it is now possible to formulate a theory of intelligent design that successfully avoids Kepler's mistake and reliably locates design in biological systems.
The theory of intelligent design is a theory of biological origins and development. Its fundamental claim is that intelligent causes are indispensable for explaining certain complex information-rich structures of biology, and that these causes are empirically detectable. To say intelligent causes are empirically detectable is to say there exists well-defined methods that, on the basis of observational features of the world, are capable of reliably distinguishing intelligent causes from undirected natural causes.
Many special sciences have already developed such methods for drawing this distinction — notably forensic science, cryptography, archeology, random number generation, and the Search for Extraterrestrial Intelligence. Whenever these methods detect intelligent causation, the underlying entity they uncover is a type of information known alternately as specified complexity or complex specified information.
For instance, how did the radio astronomers in the movie Contact (a movie starring Jodie Foster and based on a novel by Carl Sagan) infer the presence of extraterrestrial intelligence in the radio signals they monitored from space? The researchers ran signals through computers that were programmed to recognize many preset patterns. These patterns act as a sieve. 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 Contact researchers discovered a pattern of beats and pauses that corresponds to the sequence of all the prime numbers between 2 and 101. (Prime numbers are numbers divisible only by themselves and by one.) When a sequence begins with two beats, then a pause, three beats, then a pause ... and continues all the way to 101 beats, researchers must infer the presence of an extraterrestrial intelligence.
Accordingly, we say 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 will witness a highly complex or improbable event. Even so, you will have no reason not 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 fires arrows into a wall and then paints bull's-eyes around the arrows, the archer imposes 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.
The combination of complexity and specification convincingly pointed the radio astronomers in the movie Contact to an extraterrestrial intelligence. Specified complexity is the characteristic trademark or signature of intelligence. Specified complexity is a reliable empirical marker of intelligence in the same way that fingerprints are a reliable empirical marker of a person's presence (for the theoretical justifications see my book No Free Lunch, 2002).
Only intelligent causation gives rise to specified complexity. It follows that specified complexity lies beyond the capacity of blind material forces to generate it. This is not to say that material systems cannot exhibit specified complexity or that material processes cannot serve as a conduit for specified complexity. Material systems can exhibit specified complexity and material processes operating without intelligent direction can take preexisting specified complexity and shuffle it around. But that is not the point. The point is whether the material world (conceived as a closed system of blind, unbroken material causes) can generate specified complexity in the sense of originating it when previously there was none.
To see what is at stake, consider a Dürer woodcut. It arose by mechanically impressing an inked woodblock on paper. The Dürer woodcut exhibits specified complexity. But the mechanical application of ink to paper via a woodblock does not account for that specified complexity in the woodcut. The specified complexity in the woodcut must be referred back to the specified complexity in the woodblock which in turn must be referred back to the designing activity of Dürer himself (in this case deliberately chiseling the woodblock). Specified complexity's causal chains end with a designing intelligence.

To counter this line of reasoning, materialists assume that Dürer's mind is nothing but the material operation of his brain, which in turn is said to originate through a blind material process — evolution! But that is precisely the point in question, namely, whether intelligence is reducible to material process or transcends it. Intelligent design argues that the specified complexity in biological systems (e.g., Dürer's brain) is unaccountable in terms of blind material forces.
When properly formulated, the theory of intelligent design is a theory of information. Within such a theory, complex specified information (or specified complexity) becomes a reliable indicator of intelligent causation as well as a proper object for scientific investigation. The theory of intelligent design thereby becomes a theory for detecting and measuring information, explaining its origin, and tracing its flow. The theory of intelligent design therefore does not study intelligent causes per se but the informational pathways induced by intelligent causes. As a result, the theory of intelligent design presupposes neither a creator nor miracles. The theory of intelligent design is theologically minimalist. It detects intelligence without speculating about the nature of the intelligence.
In Darwin's Black Box, biochemist Michael Behe shows how specified complexity can be connected to biological design. There he defines a system as irreducibly complex if it consists of several interrelated parts so that removing even one part destroys the system's function. For Behe, irreducible complexity is a sure indicator of design. One irreducibly complex biochemical system that Behe considers is the bacterial flagellum. The flagellum is an acid-powered rotary motor with a whip-like tail that spins up to 100,000 rpm and whose rotating motion enables a bacterium to navigate through its watery environment.
Behe shows that the intricate machinery in this molecular motor — including a rotor, a stator, O-rings, bushings, and a drive shaft — requires the coordinated interaction of at least thirty complex proteins and that the absence of any one of these proteins would result in the complete loss of motor function. Behe argues that the Darwinian mechanism is in principle incapable of generating such irreducibly complex systems. In No Free Lunch I argue that Behe's notion of irreducible complexity is a special case of specified complexity and that systems like the bacterial flagellum exhibit specified complexity and are therefore designed.
In applying the test of specified complexity to biological organisms, design theorists focus on identifiable systems — such as individual enzymes, molecular machines, and the like — that exhibit a clear function and for which complexity can be reasonably assessed. Of course, once specified complexity is exhibited by some part of an organism, then any design attributable to that part carries over to the whole organism. It is not necessary to demonstrate that every aspect of the whole organism is the result of design. Some aspects will be the result of purely material forces.
Design has had a turbulent intellectual history. The chief difficulty with design to date has been to discover a conceptually powerful formulation of it that will fruitfully advance science. It is the empirical detectability of intelligent causes that promises to make the theory of intelligent design a full-fledged scientific theory and distinguishes it from the design arguments of philosophers and theologians, or what has traditionally been called "natural theology."
The world contains events, objects, and structures that exhaust the explanatory resources of undirected natural causes and that can be adequately explained only by recourse to intelligent causes. The theory of intelligent design demonstrates this rigorously. It thus takes a long-standing philosophical intuition and transforms it into a scientific research program.

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