I’m sure we all get the humor of describing evolution as “only a theory..like gravity.” (It’s an obvious play on creationists’ attempts to diminish evolution by labeling it “only a theory.”)

Scientists don’t argue about whether something’s a “theory” or a “law.” It’s not a scientific question. It’s not even a meaningful question. These are archaic terms inherited from the early days of science, and most particularly, philosophers of science. They roll easily off the tongue, but they do as much harm as good and I think we’d be far better off without them!

As for evolution by natural selection…. A century-and-a-half ago (when Darwin first proposed it) one could reasonably have classified the idea as hypothesis. Soon it was so well supported that (by any measure!) it graduated to something “better.”

So what is it now? Anyone who knows any biology or paleontology realizes that evolution by natural selection is as firmly established as the Earth’s roundness. More to the point, unless you suppose that: 1) there’s no variation within a population; or 2) all variants are equally likely to leave descendants; or 3) there’s no such thing as inheritance…. Unless you can assert at least one of these, evolution is nothing less than alogical imperative!

Whether you call it theory, law, or something else…. It’s reality.

You may find this helpful:

“At a fundamental level, popular English and scientific usage are at odds here. In popular culture, a “theory” is understood to be a guess or speculation that may or may not be based upon evidence and analysis. In science, a theory is ‘a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.’ (Teaching About Evolution and the Nature of Science,National Academy of Sciences, 1998: 7). A scientific theory is the larger explanation of how the well-tested ‘laws’ fit together to describe the natural world.”

Read more at http://www.space.com/searchforlife/seti_devore_theory_050303.html

Here is another:

“Laws are generalizations, principles or patterns in nature and theories are the explanations of those generalizations” (Rhodes & Schaible, 1989; Homer & Rubba, 1979; Campbell, 1953).

Hey, Einstein.

Gravity is what is known as, um, a LAW of science. Evolution is what is known as, um, a THEORY. Breaking news … they are NOT, um, the same thing. Makes me kind of skeptical of, um, your skepticism (as well as, um, your intelligence).