Detecting Design in the Natural Sciences
By William A. Dembski
How a designer gets from thought to thing is, at least in broad strokes,
straightforward: (1) A designer conceives a purpose. (2) To accomplish that
purpose, the designer forms a plan. (3) To execute the plan, the designer
specifies building materials and assembly instructions. (4) Finally, the
designer or some surrogate applies the assembly instructions to the building
materials.
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.
But suppose a detailed causal history is lacking and we are not able to trace
the design process. Suppose instead that all we have is an object, and we must
decide whether it emerged from such a design process. In that case, how do we
decide whether the object is in fact designed? If the object in question is
sufficiently like other objects that we know were designed, then there may be
no difficulty inferring design. For instance, if we find a scrap of paper with
writing on it, we infer a human author even if we know nothing about the
paper's causal history. We are all familiar with humans writing on scraps of
paper, and there is no reason to suppose that this scrap of paper requires a
different type of causal story.
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.
Darwin's theory is a case in point. According to Darwinist Francisco Ayala,
"The functional design of organisms and their features would therefore seem to
argue for the existence of a designer. It was Darwin's greatest accomplishment
to show that the directive organization of living beings can be explained as
the result of a natural process, natural selection, without any need to resort
to a Creator or other external agent. The origin and adaptation of organisms in
their profusion and wondrous variations were thus brought into the realm of
science."
Is it really the case, however, that the directive organization of living
beings can be explained without recourse to a designer? And would employing a
designer in biological explanations necessarily take us out of the realm of
science? The answer to both questions is No.
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.
Why? There is 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
numbers but a mathematically significant one — the prime
numbers).
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.