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Index to Creationist Claims,  edited by Mark Isaak,    Copyright © 2004
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Claim CI111.1:

Specified complexity is a reliable criterion for detecting design. The complexity-specification criterion successfully avoids false positives -- in other words, whenever it attributes design, it does so correctly.


Dembski, William A., 2002. No Free Lunch, Lanham, MD: Rowman & Littlefield, pp. 24-25.


  1. Complexity-specification allows false positives because it does not consider the combination of regularity and chance acting together, and it does not consider unknown causes.

  2. Specific examples of false positives are irreducibly complex structures for which plausible evolutionary origins have been found.

    Another false positive is canals on Mars. Percival Lowell saw that many Martian canals meet at each of several points. The odds of this happening by chance, he calculated, are less than 1 in 1.6 × 10260, proving that Mars must be inhabited (Lowell, 1907). We now know that the canals were optical illusions caused by the human mind connecting indistinct features.

  3. Dembski himself admitted the possibility of error in the same book in which he claimed reliability:
    Now it can happen that we may not know enough to determine all the relevant chance hypotheses. Alternatively, we might think we know the relevant chance hypotheses, but later discover that we missed a crucial one. In the one case a design inference could not even get going; in the other, it would be mistaken. But these are the risks of empirical inquiry, which of its nature is fallible. Worse by far is to impose as an a priori requirement that all gaps in our knowledge must ultimately be filled by non-intelligent causes. (Dembski 2002, 123)
    What Dembski fails to appreciate is that his complexity-specification criterion imposes an a priori requirement that all gaps must be filled by supernatural causes.

    Dembski also said, "On the other hand, if things end up in the net that are not designed, the criterion will be useless" (Dembski 1999, 142).


  1. Dembski, William A., 1999. Intelligent Design: The bridge between science and theology. Downers Grove, Ill.: InterVarsity Press.
  2. Dembski, William A., 2002. (see above)
  3. Lowell, Percival (as "A Mathematician"), October 26, 1907. The evidence of life on Mars: A simple mathematical proof that the canals are not due to natural causes. Scientific American, reprinted at Becker, Barbara J., 2003. History 135C: Exploring the Cosmos,

Further Reading:

Ratzsch, Del, 2001. Nature, Design and Science. Albany: State University of New York Press. (The appendix addresses false positives and other problems with Dembski's explanatory filter.)
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