"Just telling them they are wrong is not going to be effective," he said.

Instead, he told the volunteers that when they encounter religious fundamentalists they should emphasize that science museums live by the rules of science. They seek answers in nature to questions about nature, they look for explanations that can be tested by experiment and observation in the material world, and they understand that all scientific knowledge is provisional -- capable of being overturned when better answers are discovered.

"Is it against all religion?" he asked. "No. But it is against some religions."

There is more than one type of creationist, he said: "thinking creationists who want to know answers, and they are willing to listen, even if they go away unconvinced"and "people who for whatever reason are here to bother you, to trap you, to bludgeon you."

Those were the type of people who confronted Dr. Durkee, a former biology professor at Grinnell College in Iowa. The encounter left her discouraged.

"It is no wonder that many biologists will simply refuse to debate creationists or I.D.ers," she said, using the abbreviation for intelligent design, a cousin of creationism. "It is as if they aren't listening."

Dr. Allmon says even trained scientists like Dr. Durkee can benefit from explicit advice about dealing with religious challenges to science exhibitions.

"There is an art, a script that is very, very helpful," he said.

A pamphlet handed out at the training session provides information on the scientific method, the theory of evolution and other basic information. It offers suggestions on replying to frequently raised challenges like "Is there lots of evidence against evolution?" (The answer begins, simply, "No.")

When talking to visitors about evolution, the pamphlet advises, "don't avoid using the word." Rehearse answers to frequently asked questions, because "you'll be more comfortable when you sound like you know what you're talking about."