Language of science I: Theories and laws

Richard Kadel misuses the meaning of “theory” as applied by most scientists today. Theory as used today hardly means “speculation based on incomplete knowledge.” In Teaching About Evolution and the Nature of Science (National Academy Press, 1998, available at http://www.nap.edu/readingroom/books/evolution98 ), a theory in science is defined as “a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.” Laws are “typically descriptions of how the physical world behaves under certain circumstances.”

There is no suggestion that either is more certain than the other. In fact, when I teach my geology, physical science, and Earth science students about the scientific method, I stress that both laws and theories are as certain as we can make them, both are testable, and in the light of new evidence, both can be modified, overturned, or replaced. The big difference is that a theory is usually explanatory, while a law is usually descriptive and often quantifiable.

To define a theory as speculation is to fall into the trap that many nonscientists have fallen into when dealing with such controversial theories as evolution. There are generally enormous amounts of data to support theories and laws. Without that data, we usually refer to “hypotheses” to suggest the greater degree of uncertainty. In fact, most laws and theories start out as hypotheses.

I do agree that Einstein’s formulations should be called laws. However, that’s not because they are more certain now; it’s because they are quantifiable and descriptive. But we still need to refer to Einstein’s theories as well, because they explain why the formulations work.