There is a confusion regarding theories, laws, and proven statements. It is particularly discomforting when it is applied to the theory of evolution. Accordingly, a theory becomes a law when it is “proven.” So, unless the theory of evolution is “elevated” to the “law” of evolution, it is “just a theory!”
Recently I participated in an ongoing conversation on Twitter regarding theories and laws. As I tried to argue that there were no “proofs” in physics, and that nothing except mathematical theorems could be “proven,” one participant invited me to “try testing law of universal gravitation [LUG]” by going to my roof and jump! It is clear that the participant is confusing a “test” with a “proof.”
The demand for a proof is a powerful argument that creationists and intelligent designers use to refute evolution. Since a test is really an experimental test – as evident by the example of gravity and jumping from a rooftop – equating “proof” with “test” is tantamount to the age old creationists’ argument of repeatability: if you can’t turn a fish into a human being in your lab, your theory of evolution is just that … a theory without “proof.” To creationists, Lab experiments in which bacteria exhibit evolutionary adaptations do not constitute a “proof!” But what exactly is a proof?
When you construct a right triangle with sides of lengths 3, 4, and 5, you are testing the Pythagoras theorem. When you construct another right triangle with sides of lengths 5, 12, and 13, you are testing the Pythagoras theorem one more time. There are an infinitude of right triangles “testing” Pythagoras theorem. You can test its validity a zillion times. That does not prove Pythagoras theorem! A proof is a general mathematical statement – which encompasses all those zillion tests – based on a few “obvious” and unprovable postulates, in this case, the five postulates on which the entire Euclidean geometry is based.