Albert Einstein used the term “principle of relativity.” My dictionary defines a principle as “a fundamental law that describes how a thing moves, works, or acts,” which seems quite appropriate. Perhaps we would honor Einstein best by using his own words.

I actually prefer the word “theory” despite the pejorative view held by the general public. It reminds us that scientific theories cannot be proved, but only disproved. We always exist in a state of incomplete knowledge. When someone says to me that evolution is only a theory, I like to point out that gravity is also a theory, and a very useful one at that.