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[[Image:Explanfilter.jpg‎|thumbnail|275px|right|William Dembski's explanatory filter]]

[[Image:Explanfilter.jpg‎|thumbnail|275px|right|William Dembski's explanatory filter]]

Dr. [[William Dembski]] is a leading [[intelligent design]] theorist, and has written several books on the subject, including ''Intelligent Design: The Bridge Between Science & Theology'',<ref>http://www.amazon.com/Intelligent-Design-Between-Science-Theology/dp/083082314X/ref=pd_bbs_sr_2/104-1803249-2067114?ie=UTF8&s=books&qid=1194228951&sr=1-2</ref> and ''The Design Inference: Eliminating Chance through Small Probabilities (Cambridge Studies in Probability, Induction and Decision Theory)''.<ref>http://www.amazon.com/Design-Inference-Eliminating-Probabilities-Probability/dp/0521678676/ref=sr_1_7/104-1803249-2067114?ie=UTF8&s=books&qid=1194229141&sr=1-7</ref>  Dr. Dembski has a Ph.D. in mathematics and philosophy, and an M.Div. from Princeton Theological Seminary.  One of Dembski's contributions to the intelligent design movement is to set forth one method of detecting design, a method he describes as the [[Explanatory Filter]].

Dr. [[William Dembski]] is a leading [[intelligent design]] theorist, and has written several books on the subject, including ''Intelligent Design: The Bridge Between Science & Theology'',<ref>http://www.amazon.com/Intelligent-Design-Between-Science-Theology/dp/083082314X/ref=pd_bbs_sr_2/104-1803249-2067114?ie=UTF8&s=books&qid=1194228951&sr=1-2</ref> and ''The Design Inference: Eliminating Chance through Small Probabilities (Cambridge Studies in Probability, Induction and Decision Theory)''.<ref>http://www.amazon.com/Design-Inference-Eliminating-Probabilities-Probability/dp/0521678676/ref=sr_1_7/104-1803249-2067114?ie=UTF8&s=books&qid=1194229141&sr=1-7</ref>  Dr. Dembski has a Ph.D. in mathematics and philosophy, and an M.Div. from Princeton Theological Seminary.  One of Dembski's contributions to the intelligent design movement is to set forth one method of detecting design, a method he describes as the '''explanatory filter'''.

Dembski describes his three-part '''Explanatory Filter''' together with an example of its use in a paper published at '''Access Research Network'''.<ref>http://www.arn.org</ref> In the paper, entitled ''The Explanatory Filter: A three-part filter for understanding how to separate and identify cause from intelligent design'',<ref>http://www.arn.org/docs/dembski/wd_explfilter.htm</ref>

Dembski describes his three-part explanatory filter together with an example of its use in a paper published at '''Access Research Network'''.<ref>http://www.arn.org</ref> In the paper, entitled ''The Explanatory Filter: A three-part filter for understanding how to separate and identify cause from intelligent design'',<ref>http://www.arn.org/docs/dembski/wd_explfilter.htm</ref>

Dembski found that all formal design detection methodologies can be reduced to three logical steps in what he refers to as an explanatory filter.  The filter first asks whether a given pattern is best explained by some chemical or physical necessity or law?  If not, can it be explained by chance.  If chance and necessity can’t explain the pattern, does it exhibit a “specification” or apparent purpose?  If a complex pattern reflecting the integration of numerous stopping points does exhibit purpose and can’t be explained by chance or necessity, then the scientific, logical inference to the best explanation is design.

Dembski found that all formal design detection methodologies can be reduced to three logical steps in what he refers to as an explanatory filter.  The filter first asks whether a given pattern is best explained by some chemical or physical necessity or law?  If not, can it be explained by chance.  If chance and necessity can’t explain the pattern, does it exhibit a “specification” or apparent purpose?  If a complex pattern reflecting the integration of numerous stopping points does exhibit purpose and can’t be explained by chance or necessity, then the scientific, logical inference to the best explanation is design.

=====Explanatory Filter Step 1 – Ruling Necessity In or Out=====

=====Explanatory Filter Step 1 – Ruling Necessity In or Out=====

Step one of the Explanatory Filter asks if some physical or chemical ''necessity'' explains the apparent design of a natural object.  Consider, for example, a snowflake or salt crystal.  Is a snowflake or a salt crystal a design or an occurrence? That is, can a snowflake or salt crystal be explained as being a necessity constrained by known, immutable laws of physics?  The answer is yes.  Taking a snowflake as an example, the physical properties of hydrogen and oxygen ions that form H2O under certain conditions of temperature and pressure produce intricate hexagonal shapes by known physical laws of thermodynamics.  Accordingly, one need not invoke an intelligence cause to explain a snowflake or salt crystal.   

Step one of the explanatory filter asks if some physical or chemical ''necessity'' explains the apparent design of a natural object.  Consider, for example, a snowflake or salt crystal.  Is a snowflake or a salt crystal a design or an occurrence? That is, can a snowflake or salt crystal be explained as being a necessity constrained by known, immutable laws of physics?  The answer is yes.  Taking a snowflake as an example, the physical properties of hydrogen and oxygen ions that form H2O under certain conditions of temperature and pressure produce intricate hexagonal shapes by known physical laws of thermodynamics.  Accordingly, one need not invoke an intelligence cause to explain a snowflake or salt crystal.   

However, can physical and chemical necessity explain the particular sequence of genetic symbols of DNA that carry the messages of life?  Interestingly, the answer is no.  The genetic symbols consisting of nucleotide bases of adenine, guanine, thymine and cytosine (AGTC) can be arranged in any order.  Unlike the chemistry of a snowflake or salt crystal, the physical and chemical properties of the four genetic symbols, like dots and dashes in a Morse code message, can hook into any position along the sugar-phosphate backbone of DNA.  Just as the letters on this page can be ordered in any sequence, the genetic symbols that specify the letters of life can be arranged in any order to communicate a nearly infinite variety of messages.    Watson and Crick predicted this peculiar characteristic, for if the structure of DNA were driven by law, it could not carry the information necessary to generate the seemingly infinite variety of life:

However, can physical and chemical necessity explain the particular sequence of genetic symbols of DNA that carry the messages of life?  Interestingly, the answer is no.  The genetic symbols consisting of nucleotide bases of adenine, guanine, thymine and cytosine (AGTC) can be arranged in any order.  Unlike the chemistry of a snowflake or salt crystal, the physical and chemical properties of the four genetic symbols, like dots and dashes in a Morse code message, can hook into any position along the sugar-phosphate backbone of DNA.  Just as the letters on this page can be ordered in any sequence, the genetic symbols that specify the letters of life can be arranged in any order to communicate a nearly infinite variety of messages.    Watson and Crick predicted this peculiar characteristic, for if the structure of DNA were driven by law, it could not carry the information necessary to generate the seemingly infinite variety of life:

   

   

=====Explanatory Filter Step 2 – Ruling Chance In or Out=====

=====Explanatory Filter Step 2 – Ruling Chance In or Out=====

Taking the second step of the Explanatory Filter, if necessity can’t explain a pattern, such as the patterns in DNA, then perhaps chance can explain it.  Perhaps random assortments of chemicals came together to produce the first messages of life, for example.  After life got started, maybe random mutations in the initial messages would occasionally generate positive functional novelty that would be embraced by the environment.  Is 4 billion years enough time for a chance process to turn rocks into intelligent beings that have the capacity to use them for a purpose?  

Taking the second step of the explanatory filter, if necessity can’t explain a pattern, such as the patterns in DNA, then perhaps chance can explain it.  Perhaps random assortments of chemicals came together to produce the first messages of life, for example.  After life got started, maybe random mutations in the initial messages would occasionally generate positive functional novelty that would be embraced by the environment.  Is 4 billion years enough time for a chance process to turn rocks into intelligent beings that have the capacity to use them for a purpose?  

Calculating the odds is not always easy because one cannot always know all the steps necessary to get from point A to point B – to get from no life to life.  Darwin could not even look into the cell, much less count the steps, the number of times matter would have to be precisely stopped and started to get life.  Also, the possible alternatives at each step are not easy to ascertain.  A calculation of probability requires one to divide a particular outcome (e.g., heads in a coin flip), by the number of possible different outcomes (two – heads or tails), times the number of opportunities for the outcome to occur (the number of flips available).  If a stadium is filled with 10,000 flippers, we would expect about five flippers to get ten heads in a row, the odds of which are 1 over 2,048.  This is because 10,000 times 1/2048 is 4.88.  But what if one needed 500 heads in a row, or a very specific sequence of 500 heads and tails or zeros and ones?  How many people would one need in the stadium?  How many monkeys banging away at typewriters could be expected to generate the first sentence of the Gettysburg address?

Calculating the odds is not always easy because one cannot always know all the steps necessary to get from point A to point B – to get from no life to life.  Darwin could not even look into the cell, much less count the steps, the number of times matter would have to be precisely stopped and started to get life.  Also, the possible alternatives at each step are not easy to ascertain.  A calculation of probability requires one to divide a particular outcome (e.g., heads in a coin flip), by the number of possible different outcomes (two – heads or tails), times the number of opportunities for the outcome to occur (the number of flips available).  If a stadium is filled with 10,000 flippers, we would expect about five flippers to get ten heads in a row, the odds of which are 1 over 2,048.  This is because 10,000 times 1/2048 is 4.88.  But what if one needed 500 heads in a row, or a very specific sequence of 500 heads and tails or zeros and ones?  How many people would one need in the stadium?  How many monkeys banging away at typewriters could be expected to generate the first sentence of the Gettysburg address?