In everyday language, a "theory" is "a guess" or "a hunch." In science, however, it's much more. It's a rational explanation for a series of observations, independently verified by other scientists. No scientific theory has been as controversial in the United States as Darwin's Theory of Evolution. For the past few months it's been a hot topic in the state of Kansas, where the state board of education is seen as likely to vote to downplay evolution's teaching in public schools. Critics suspect the move is an attempt by the board's conservative members to introduce a religious explanation of how the world was created.

The controversy has its roots in last year's elections, when conservatives took control of the school board. The new conservative majority does not believe Darwinian evolution should be taught in a vacuum. Board President Steve Abrams, a veterinarian, says he doesn't believe that life on Earth evolved from a common origin, "from an ameba to bacteria to some crawling thing that ended up as you and I standing here. I don't believe that."

And neither does Doctor William Harris, a Christian and co-founder of an organization known as the Intelligent Design Network. "Are we going to teach Darwin honestly?" he asks. "Are we going to be upfront with the strengths and the weaknesses?" One of those weaknesses, he says, is science's failure to validate Darwin's theory by demonstrating, for example, how life could come from non-life.

Doctor Harris, a physician and researcher in Kansas City, says he believes that living things are best explained by an intelligent force - a creator - rather than by an undirected process. He uses for an illustration the giant sculpted faces of four U.S. presidents on Mount Rushmore. "You drive by faces carved on a mountain in South Dakota, you know that it wasn't wind and rain and water that did that," he says. "You don't need to know the name of the guy who did it or when he did it or why or how, to know it was designed. You can recognize design when you see it. It's got fingerprints."

Biologist David McDonald also turns to an analogy as he explains that the goal of science is not to prove something. "It's just like a lawyer in a courtroom," he says. "We try to come up with an interpretation that speaks to the weight of the evidence." The Wichita State University biological sciences professor challenges the notion of an intelligent designer. He says that a preponderance of evidence supports the Theory of Evolution, based in part by the similarities shared by living things that may look very different.

"All living things encode information in DNA. They have similar metabolic pathways; many aspects of their physiology are also similar," he points out. "So here you have two things which appear to be in conflict -- apparent differences -- but actually an abiding amount of similarity. Evolution helps us to understand that. Evolution says, the reason why you're seeing this is that all these living things, however different they might appear at first glance, are derived from a common progenitor. Now it's not just an idea to help us accommodate those, in fact there's a great deal of evidence to support that."

Beyond the question of scientific evidence is what critics see as the unstated religious basis of "intelligent design." Pedro Irigonegaray, a Kansas attorney who defended evolution before the state school board, says teaching intelligent design in a public school would violate the U.S. Constitution by bringing religion into the classroom.

"Intelligent Design is not a theory, it's not even a hypothesis. It's a religious belief," he says. "And if Intelligent Design had serious scientific merit they should bring it to the attention of the scientific community, not in front of a board of education whose mind is already made up and who's willing to do what ever it takes to open the doors to their theistic views to be introduced into our science curriculum."

The State Board of Education seems poised to de-emphasize evolution in the curriculum, but board president Steve Abrams denies that they plan to replace it entirely. "What I am suggesting is that there are other scientists -- not the majority but certainly a strong minority -- who say that [Darwin's theory of evolution] is not true," he says. "And they have different understandings about that. And have testing about it and have data to support their point of view. And what I'm saying is that students need to critically analyze that." The Board is expected to make its final decision in August.