The signs of design
How would we come to know that something was
intelligently designed? Its very straightforward, says Dembski.
There does in fact exist a rigorous criterion for discriminating
intelligently caused from unintelligently caused objects. ... I call it the complexity-specification criterion. When intelligent agents
act, they leave behind a characteristic trademark or signature - what I define as
specified complexity. The complexity-specification criterion detects design by
identifying this trademark of designed objects.
Whenever we infer design we must establish three things: contingency, complexity, and
An object/event is said to be contingent if, while it is fully consistent with natural
laws, it is not wholly determined by them and represents only one outcome among
several possible outcomes of natural processes. Complexity
is related inversely to probability. Highly complex objects have a low
probability of being actualized naturally. Dembski looks for objects whose
probability of actualization by natural means is less than what he calls the
universal probability bound, which has the value 10 - 150. For some
event/object to be specified it
must exhibit a distinctive pattern that is detachable from
the particular event/object itself. A detachable pattern might, for instance,
correspond to some independently derivable sequence of numbers or letters that
has no necessary connection to the object/event being subjected to the
complexity-specification criterion. For example, if SETI researchers received a
radio signal representing the first 100 prime numbers they would be justified
in concluding that the signal exhibited a detachable pattern that had no
necessary relationship to the electromagnetic waves that carried it.
In Dembskis language, if some event/object is contingent (not the outcome of any deterministic natural
law), and sufficiently complex (its probability of
natural actualization is less than 10 - 150), and specified,
then it exhibits specified complexity. The central
argument of No Free Lunch is that objects/events
that exhibit specified complexity cannot be actualized by natural
processes alone and must, therefore, be the outcome of intelligent design, in the sense consistent with the way in
which all of the key terms have been defined above.
Establishing the contingency of some
event/object is ordinarily a rather simple matter. Establishing complexity and
specification, however, is difficult (perhaps impossible), as our case study of
the bacterial flagellum will illustrate.
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| Contributed by: Dr. Howard Van