Creationists frequently stress the fact that evolution is "only a theory", giving the impression that a theory is an idle guess. A scientist, one gathers, arising one morning with nothing particular to do, decided that perhaps the moon is made of Roquefort cheese and instantly advances the "Roquefort-cheese theory".

A theory (as the word is used by scientists) is a detailed description of some facet of the universe's workings that is based on long observation and, where possible, experiment. It is the result of careful reasoning from these observations and experiments that has survived the critical study of scientists generally. For example, we have the description of the cellular nature of living organisms (the "cell theory"); of objects attracting each other according to fixed rule (the "theory of gravitation"); of energy behaving in discrete bits (the "quantum theory"); of light traveling through a vacuum at a fixed measurable velocity (the "theory of relativity"), and so on.

All are theories; all are firmly founded; all are accepted as valid descriptions of this or that aspect of the universe. They are neither guesses nor speculations. And no theory is better founded, more closely examined, more critically argued and more thoroughly accepted, than the theory of evolution. If it is "only" a theory, that is all it has to be.

Creationism, on the other hand, is not a theory. There is no evidence, in the scientific sense, that supports it. Creationism, or at least the particular variety accepted by many Americans, is an expression of early Middle Eastern legend. It is fairly described as "only a myth".