The wonders of the Internet; overcoming dreaded diseases such as polio; our first steps to explore space; the ability to locate anything on Earth to within a few feet with a global positioning system -- all are powerful reminders that science and technology can change the world in a most positive manner. They have a wonderful opportunity to play in shaping the society we live in -- but they cannot do that successfully if science is allowed to become simply a matter of opinion.

Just look at what has been happening in regard to scientific questions about the environment, global warming and evolution. Why is scientific opinion so often disregarded, or even scoffed at? The answer is the growing public sentiment that science is only one of many ways of viewing the world. All of us should be troubled by this trend, because it threatens to make our nation less competitive at a time when the globe is shrinking.

Perhaps this failure is most evident in terms of evolution. Polls are a useful way to gauge what the public is thinking. In a Gallup poll in November, respondents were asked: "Do you think that Charles Darwin's theory of evolution is: a scientific theory that has been well supported by evidence; just one of many theories that has not been well-supported by evidence; or don't know enough to say?" Only 35 percent of Americans indicated a scientific theory supported by evidence, whereas an equal percentage indicated that evolution was just one among many theories, and 29 percent answered that they didn't know.

A December 2004 Newsweek poll asked its readers "In general do you favor or oppose teaching creation science in addition to evolution in public schools?" Sixty percent favored the idea, 28 percent were opposed, and 12 percent were undecided.

Yes, I mention the E word, evolution -- a word that high-school science teachers increasingly avoid using in their classes for fear of the reaction of parents and the lack of support from school administrators. Because science cannot prove anything, creationists argue that scientific theories are arbitrary and so, in the end, decisions must be made by appeal to a higher authority.

All thinking persons should be troubled by this trend, because it devalues the basic scientific method that has proved its power over and over again by its successes in explaining the basic nature of the physical universe, ranging from the forces that power the stars, the manner in which the solar system is organized, the molecular and genetic nature of life, down to the atomic nature of matter. Scientific theories are constructed painfully, piece by piece, by testing each small piece against the behavior of nature. The pieces are assembled and reassembled in different ways. The overall structure is tested for logical consistency and used to make predictions of how the system in question will perform in novel circumstances. Those predictions are compared with what actually happens.

No scientific theory is absolutely sure, but it is something you can bet on, such as the sun rising tomorrow in the East and setting in the West. Compare this mode of viewing the world with other ways, often religious, that start with conclusions that are considered to be true and work backward from them.

I want to emphasize that science and faith are not in opposition. I know many scientists who are deeply religious. (Charles H. Townes, one of the inventors of the maser and the laser, just won the $1.5 million Templeton Prize for Progress Toward Research or Discoveries about Spiritual Realities.) But claims of faith that fly against scientific findings are just not sensible.

What has brought about this questioning of science? The answers can be found in many places, from the difficulty scientists have in explaining to nonscientists what they do to the lack of understanding by the news media, who think that "fair and balanced" means giving equal weight to all opinions, or are unwilling or unable to distinguish between scientific fact and opinion, observation and philosophy.

But a particularly discomforting aspect is the failure of national leadership, where so many in high places wink, nod and even, on occasion, give direct support to the know-nothings. For example, President Bush believes that the jury is still out about evolution. He told the Associated Press on Nov. 14: "I'd make it a goal to make sure that local folks got to make the decision as to whether or not they said creationism has been a part of our history and whether or not people ought to be exposed to different theories as to how the world was formed."

It is easy to list other examples from statements by leading politicians denying global warming to those championing that the only thing we need to do for an energy policy is to search for more oil.

Ideas do not fight for themselves; they are fought for by people. It is not enough to know the importance of the scientific approach. Being quiet or being vocal is like being intelligent or being smart. We can have an influence. We must be willing to speak out against the threat of making science just a matter of opinion. Scientific theories are more than a special set of opinions that the scientific community is trying to push onto the public in opposition to religious beliefs. To pretend otherwise is to invite the decline of our nation.

Richard N. Zare is the Marguerite Blake Wilbur professor of natural science in the Chemistry Department at Stanford University. From 1992-1998, he served as a member of the National Science Board, under former Presidents Bush and Clinton, the last two years as chairman. In May, he will receive the Wolf Prize in chemistry.

This article appeared in the San Francisco Chronicle on Thursday, April 28 2005 and is reproduced here by permission of the author, Richard Zare.