NCSE has long taken the position that it is not productive for scientists to debate creationists (see "Confronting Creationism: When and How", p 23). However, NCSE has figured indirectly in a series of seven debates that I have had since 1989 with Duane Gish from the Institute for Creation Research (ICR).
I have participated in these debates even though I understand the downside of debating creationists: scientific evidence will never convince biblical literalists of the validity of the scientific position, and debates give creationism more stature than it deserves, reinforcing the false claim that evolutionary theory is actively being debated by scientists. However, I have been persuaded by two counterarguments. First, all the debates I have participated in have been attended by some people "on the fence" (see "Then a miracle occurs", p 32) who are receptive to evaluating the evidence for evolution. A few of these folks have come up to me after debates and thanked me for helping them to reposition their views on evolution. For these folks I feel the debate has been a success; and for those unconvinced, I hope they see that it is possible to discuss scientific evidence for evolution without explicitly challenging the validity of religious faith. Second, if no one volunteers to present the evolutionist position, the creationists make hay out of this, claiming that evolutionists have so little to support their view that they are afraid to debate.
One other downside of debating creationists is that scientists who are knowledgeable about evolution are not necessarily knowledgeable about creationist claims and tactics; and if they debate without this knowledge they can be made to look like fools even though their arguments are scientifically sound. I have tried to avoid this pitfall by reading creationist books and articles and by coming to the debates prepared to address specific creationist claims (see "Winning the creation debate", p 36).
I have opened all my debates by explaining that I was not out to destroy anyone's faith in the Bible, but hoped to dissuade the faithful from relying on the flimsy arguments of "creation science". I introduce the idea that creationism is "non-professional" science, that is, it is based on arguments that have not passed peer-review in professional scientific journals. I distinguish between creation scientists (who may have professional degrees, usually in a field unrelated to evolution) and their creationist claims, which are absent from the professional science literature. To pre-empt the creationist response — that professional journal editors are prejudiced against creationism — I assert that the rejection of creationist arguments is entirely justified by their poor standards of scholarship; and I spend a lot of debate time showing examples of that poor scholarship in major creationist claims. In each case I show how the creationist claim is superficially appealing, so that it sounds reasonable to church audiences not trained as professional scientists; then I explain why the claim could not pass professional peer review. My bottom line is that a faith-based view of creation is fine, but that science classrooms should stick to science that can pass professional peer-review.
One of the creationist claims that I have tried to counter at all my debates is that the Second Law of Thermodynamics would be violated by the evolutionist model of species origins. I show that Gish's Second Law claim is flawed because he fails to recognize that examples of localized negative entropy do not violate the Second Law if they are outweighed by positive entropy elsewhere in the system so that the net entropy is positive. In particular, when Gish claims that the evolution of complex life in the biosphere represents negative entropy in violation of the Second Law, his conclusion is completely invalid because he fails to consider whether this localized negative entropy is outweighed by positive entropy effects such as entropy due to energy radiation from the biosphere into space. Thus Gish's Second Law claim is as invalid as that of an accountant who claims a net profit on the basis of a high gross income, but ignores the possibility that the income is outweighed by expenses.
In my first debate with Gish, I argued that a debate before a non-technical audience would not be an appropriate venue to discuss the details of thermodynamic analyses of the evolution. I challenged him to prepare a technical article supporting his argument, suitable for publication in a professional journal. And, after getting agreement from Fred Edwords, then editor of Creation/Evolution, I told him that his article would be granted publication in this journal, where it could be evaluated by scientists interested in creation "science" arguments. He would not have to worry about journal referees rejecting his article out of prejudice; so this venue would be perfect for putting his ideas before an interested community with science training. I had a copy of this challenge distributed to everyone in the audience, and showed a slide of a letter from the journal inviting Gish's contribution. Before each subsequent debate, I have obtained a renewal of the invitation to Gish from the editor of Creation/Evolution and subsequently of RNCSE. So at each of my recent debates, when I point out that creation "scientists" make claims that sound good at non-technical debates, but that they do not even try to meet the standards of scholarship that would be acceptable for professional scientists, I can cite the NCSE's still open invitation to accept my challenge, which Gish has sidestepped since 1989.
Gish's reaction, of course, underlines the inference that we draw from the use of the debate format before a general audience: the arguments do not work in a scientific setting as science. When challenged to a real exchange of scientific ideas and theories, creationists have nothing to bring to the table.