Intelligent Design creationist Stephen Meyer and his online followers are upset that in our big debate I did not specifically address his claims about inferring design in complex structures such as DNA. I will do so now. By way of background, they note:

Intelligent design scientists like Meyer argue in favor of design theory based on the recognition of things like the digital information in DNA and the complex molecular machines found in cells. As Meyer patiently explained to Shermer in the debate, they do so because invariably we know from experience that complex systems possessing such features always arise from intelligent causes.

As Meyer explains (“Word Games: DNA, Design, and Intelligence.” Touchstone, Vol. 12, No. 4, 44-50): “Design theorists infer a prior intelligent cause based upon present knowledge of cause-and-effect relationships. Inferences to design thus employ the standard uniformitarian method of reasoning used in all historical sciences, many of which routinely detect intelligent causes.” Archaeologists, for example, employ criteria to discriminate between natural-made and human-made artifacts. “Intelligent agents have unique causal powers that nature does not. When we observe effects that we know only agents can produce, we rightly infer the presence of a prior intelligence even if we did not observe the action of the particular agent responsible.” DNA, for example, was no more naturally designed than the pyramids. If it looks intelligently designed, it was.

I have four objections to this argument:

1. The inference to design is subjective. Sometimes it is obvious, other times it is not. There is an obvious difference between the face on Mars that is an eroded mountain and a face on Mount Rushmore that is an intelligently designed (carved) President’s face. But the difference between, say, a rock and a chipped-stone tool made by an Australopithicene three million years ago is not obvious.
2. The inference to design is specific to each claim. In the chipped-stone problem, a rock that has been chipped on both sides in a symmetrical fashion is more likely to be intelligently designed than naturally flaked. Nevertheless, archaeologists infer many false positives, and there is no sure-fire design inference algorithm that applies to all archaeological problems, let alone one that applies to all scientific fields. The set of criteria used by archaeologists to determine whether a stone was chipped by chance or design is completely different from the set of criteria used by astronomers to determine whether a signal from space is natural or artificial.
3. We perceive nature to be intelligently designed because of our experience of human artifacts that we know are intelligently designed since we can observe them being made and we have vast experience with human artificers. We know an intelligently designed PDA (Personal Digital Assistant) when we see one. By contrast, we have no experience with an intelligent designer outside of the human realm, and no experience with a supernatural agent outside of inferring his existence through gaps in our knowledge of mysteries as yet unexplained. What experience do we have of structures such as DNA being created by which we could construct an a design inference algorithm? None.
4. We must be cautious about inferring design because our experience with intelligently-designed artifacts in our culture biases us to see intelligent design where none exists (for example, Virgin Mary apparitions on glass panes). Long before Darwin debunked William Paley’s watchmaker argument, the Enlightenment philosopher Voltaire satirized this problem in his classic novel Candide through his character Dr. Pangloss, a professor of “metaphysico-theology-cosmolonigology”: “Tis demonstrated that things cannot be otherwise; for, since everything is made for an end, everything is necessarily for the best end. Observe that noses were made to wear spectacles; and so we have spectacles. Legs were visibly instituted to be breeched, and we have breeches.”