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Unlike creationists, the founders of the intelligent design movement, notably Michael Behe, William Dembski, Phillip Johnson and Jonathan Wells, have respectable academic credentials and generally accept the overall scientific account and timeline of the creation. However, they still insist that many features of life on earth are too complex to be explained by natural evolution. They generally acknowledge limited variations within basic "kinds," but insist that the individual kinds were separately formed or designed by an intelligent entity, utilizing means that may not be subject to human investigation [Behe1996; Behe2007; Dembski1998; Dembski1999; Dembski2002; Dembski2007; Johnson1993; Johnson2000; Wells2000]. Intelligent design writers generally agree with creationists that evolution is fundamentally irreconcilable with Christian religion. John G. West of the Discovery Institute, which sponsors much of the intelligent design work, says that theistic evolution would require "radical revisions in how one view God." West openly criticizes, by name, some of the scientists and theologians who have spoken for a moderate middle ground [West2007; West2009].

Intelligent design writers and their proponents take pains to distinguish themselves from traditional creationists, but it is clear that both the creationist and intelligent design movements are connected to the conservative Christian world. Each of the four prominent intelligent designscholars mentioned above (except for Michael Behe, who is Catholic) is affiliated with an evangelical denomination, and all have acknowledged that religious beliefs are a principal motivation for their work. The intelligent design-authored textbook Of Pandas and People is a lightly edited version of an earlier creationist textbook, where, among other things, the word "creation" has been replaced with "intelligent design." [Kitzmiller2005]. The Discovery Institute's Center for Science and Culture, is devoted "to defeat scientific materialism and its destructive moral, cultural, and political legacies" and "to replace materialistic explanations with the theistic understanding that nature and human beings are created by God." To this end, they have outlined a "wedge" strategy, which recommends that they proceed in degrees, first by "teaching the controversy" of evolution, then promoting intelligent design as an alternative theory to evolution, then edging out evolution in favor of biblical theism [Forrest2004, pg. 25-33].

It might be pointed out that the intelligent design community's focus on "design," including the notion of "irreducible complexity," is certainly not a new notion. In fact, virtually the same arguments were first raised in the 19th century by William Paley, in his book Natural Theology. Paley asked his readers to imagine finding a pocket watch along the road. After even a cursory examination of the watch's intricate structure, one could rationally conclude that it only could have been the result of design by an intelligent being. And since nature in general and the human body in particular is much more intricate than a watch, one must conclude that we are the result of design by an intelligent Being. Paley even included arguments based on chance, and the equivalent of "irreducible complexity." [Ayala2007, pg. 15-26].

Michael Ruse, a philosopher of science who testified in the 1981 Alabama creationism case, describes science as a discipline that (1) is guided by natural law, (2) is explanatory by reference to natural law, (3) is testable against the empirical world, (4) reaches conclusions that are tentative, and (5) is falsifiable [Pennock1999, pg. 5]. So how does intelligent design measure as a scientific theory?

One key weakness of ID, as it currently stands, is that intelligent design writers have not yet produced a solid body of quantitative, falsifiable scientific hypotheses that can be tested and scrutinized by the scientific community. For example, exactly what do the intelligent design writers mean by "design"? By comparison, creationists have at least produced a number of testable hypotheses, such as the assertion that the earth is a mere 10,000 years old or less, and that fossils were deposited during a great flood (which hypotheses have been soundly refuted by scientific evidence). Instead, intelligent design writers, like creationist writers, have mostly focused their efforts on identifying weaknesses in the established evolutionary theory. One difficulty with this approach was noted by Judge John E. Jones in the Dover, Pennsylvania case: "[Intelligent design] is at bottom premised upon a false dichotomy, namely, that to the extent evolutionary theory is discredited, [intelligent design] is confirmed. ... We do not find this false dichotomy any more availing to justify [intelligent design] today than it was to justify creation science two decades ago." [Jones2005, pg. 71].

Nonetheless, many are convinced that intelligent design writers have identified substantive technical issues that draw into question certain aspects of evolutionary theory. Since these issues are very frequently raised in these discussions, here is a brief summary of the some issues raised by the intelligent design writers and the consensus response of the scientific world:

1. Irreducibly complex systems. intelligent design scholar Michael Behe has argued that certain biological systems, such as bacterial flagella, blood clotting machinery, and the immune system, are "irreducibly complex": they consist of multiple subsystems, the removal of any one of which would render the system nonfunctional. He argues that such systems must have been designed by an intelligent entity, because none of the components could have evolved in the absence of the others. Scientists counter that systems labeled as "irreducibly complex" by Behe can arise by natural evolution -- individual parts may arise separately, each useful in different context, and then later be combined into a larger system. This is discussed in more detail at Complexity.

2. Probability. Creationists and intelligent design writers have argued that the probability of a biomolecule such as human alpha globin, which is a sequence of 141 amino acids, forming at random from scratch is so remote that it could not be expected to have occurred even once in the history of the universe. Such calculations are often flawed. But more importantly, this type of probability-based arguments suffers from the fatal fallacy of presuming that a structure such as alpha globin arises by a single all-at-once event (which, after all, is the creationist theory, not the scientific theory, of their origin). Instead, available evidence suggests that alpha globin and other proteins arose as the end product of a long sequence of intermediate steps, each of which was biologically useful in an earlier context. This is discussed in more detail at Probability.

3. Information theory. intelligent design writer William Dembski has invoked probability and information theory (the mathematical theory of information content) in arguments against Darwinism. But knowledgeable researchers who have examined Dembski's works in detail are sharply critical. Mathematician Jeffrey Shallit and biologist Wesley Elsberry conclude that Dembski's notion of "complex specified information" is incoherent and unworkable [Shallit2004]. Richard Wein, in a review of Dembski's book No Free Lunch, characterizes it as "pseudoscientific rhetoric." [Wein2002]. This is discussed in more detail at Probability.

4. Biological novelty. A key premise of intelligent design theory is that whereas minor changes may occur within an established kind, "random" or "undirected" evolution can never produce anything fundamentally new [Dembski1999, pg. 113]. Biologists counter with examples such as a 1974 experiment, wherein a gene in the bacterium E. coli that is responsible for metabolizing lactose was removed. Within 24 hours the bacteria had re-evolved a capability to utilize lactose, by means of a similar but distinct three-part biochemical pathway [Hall1974, Miller1999, pg. 145-147]. Perhaps the best-known examples, however, are the recent evolution of new strains of tuberculosis that are resistant to all known anti-TB drugs, and drug-resistant strains of HIV that in many cases evolve within the body of a single patient [Coyne, 2009, pg. 130-131]. This is discussed in more detail at Novelty.

In summary, the intelligent design community, while much more accepting of the old-earth worldview than the creationists, nonetheless has failed to formulate a body of crisp, testable hypotheses that can be taken seriously by the scientific community. Instead, like creationists, intelligent design writers have focused much of their energy trying to find weaknesses in existing evolutionary theory. But, as Judge Jones pointed out in the Dover case, it is not at all clear that even if intelligent design scholars are able to find significant weaknesses in evolution, that this establishes design theory as the only alternative. And as for the various counter-arguments that intelligent design writers have raised, the consensus of the vast majority of scientists who have examined these issues is that these objections, like those raised by creationists, are either deeply flawed or not genuinely substantive. For the most part, these questions were settled long ago in the scientific literature. They certainly do not threaten the foundations of the evolutionary paradigm.

Whatever the merits or demerits of these technical issues, one overriding difficulty with the intelligent design movement, both as an approach to science and as an approach to religion, is that invoking a Designer whenever we come up against a difficult question is a "thinking stopper" -- it places numerous questions of our existence off-limits to human investigation, buried in the inscrutable mind of a mysterious Designer: Why was the earth (or the universe in general) designed the way it was? How did the design and creative processes proceed? What physical laws were employed? Why those particular laws? What prompted the Designer to proceed with this creation? Have other earths or universes been designed or created? Where are they? Surely there is a more fruitful avenue for finding a harmony between science and religion than just saying "God designed it" and then deeming it either unnecessary or inappropriate to inquire further.

References

1. [Ayala2007] Francisco J. Ayala, Darwin's Gift to Science and Religion, Joseph Henry Press, Washington, DC, 2007.
2. [Behe1996] Michael J. Behe, Darwin's Black Box: The Biochemical Challenge to Evolution, Simon and Schuster, New York, 1996.
3. [Behe2007] Michael J. Behe, The Edge of Evolution: The Search for the Limits of Darwinism, Free Press, New York, 2007.
4. [Coyne2009] Jerry A. Coyne, Why Evolution Is True, Viking, New York, 2009.
5. [Dembski1998] William A. Dembski, The Design Inference: Eliminating Chance through Small Probabilities, Cambridge University Press, 1998.
6. [Dembski1999] William A. Dembski, Intelligent Design: The Bridge between Science and Theology, InterVarsity Press, Downers Grove, IL, 1999.
7. [Dembski2002] William A. Dembski, No Free Lunch: Why Specified Complexity Cannot Be Purchased without Intelligence, Rowman and Littlefield, Lanham, MD, 2002.
8. [Dembski2007] William A. Dembski, The Design of Life: Discovering Signs of Intelligence In Biological Systems, Foundation for Thought and Ethics, Richardson, TX, 2007.
9. [Fairbanks2007] Daniel J. Fairbanks, Relics of Eden: The Powerful Evidence of Evolution in Human DNA, Prometheus Books, New York, 2007.
10. [Forrest2004] Barbara Forrest and Paul R. Gross, Creationism's Trojan Horse: The Wedge of Intelligent Design, Oxford University Press, New York, 2004, pg. 25-33.
11. [Hall1974] Barry G. Hall and Daniel L. Hartl, "Regulation of Newly Evolved Enzymes," Genetics, vol. 76 (1974), pg. 391-400.
12. [Johnson1993] Phillip E. Johnson, Darwin on Trial, InterVarsity Press, Downers Grove, IL, second edition, 1993.
13. [Johnson2000] Phillip E. Johnson, The Wedge of Truth: Splitting the Foundations of Naturalism, InterVarsity Press, Downers Grove, IL, 2000.
14. [Wells2000] Jonathan Wells, Icons of Evolution: Science or Myth?, Regnery Publishing, Washington, DC, 2000.
15. [Jones2005] Judge John E. Jones, Kitzmiller vs Dover Area School District, Memorandum Opinion, 20 Dec 2005, available at Online article.
16. [Kitzmiller2005] "Kitzmiller v. Dover Area School District: Trial transcript: Day 6 (October 5), AM Session, Part 2," available at Online article.
17. [Miller1999] Kenneth R. Miller, Finding Darwin's God: A Scientist's Search for Common Ground Between God and Evolution, Cliff Street Books, New York, 1999.
18. [Miller2008] Kenneth R. Miller, Only a Theory: Evolution and the Battle for America's Soul, Viking, New York, 2008.
19. [Pennock1999] Robert T. Pennock, Tower of Babel: The Evidence Against the New Creationism, MIT Press, Boston, MA, 1999.
20. [Shallit2004] Jeffrey Shallit and Wesley Elsberry, "Playing Games with Probability: Dembski's Complex Specified Information," in [Young2004], pg. 121-138.
21. [Wein2002] Richard Wein, "Not a Free Lunch But a Box of Chocolates: A Critique of William Dembski's Book No Free Lunch," 23 Apr 2002, available at Online article.
22. [West2007] John G. West, "Is Darwinian Evolution Compatible with Religion?," 22 Aug 2007, available at Online article.
23. [West2009] John G. West, "What is Theistic Evolution?," 1 May 2009, available at Online article.
24. [Young2004] Matt Young and Taner Edis, Why Intelligent Design Fails: A Scientific Critique of the New Creationism, Rutgers University Press, Piscataway, NJ, 2004.