Theory or Law?

If you read anything about the Intelligent Design debacle you might have heard something along these lines:

"There is still doubt about the theory of evolution, that is why it is still a theory."

This argument is really a misnomer of "theory". The word theory in the theory of evolution does not imply doubt from mainstream science regarding its validity; the concepts of theory and hypothesis have specific meanings in a scientific context. While theory in colloquial usage may denote a hunch or conjecture, a scientific theory is a set of principles that explains observable phenomena in natural terms. Evolution is a theory in the same sense as germ theory, gravitation, or plate tectonics. Put another way, a scientific theory summarizes a hypothesis or group of hypotheses that have been supported with repeated testing. A theory is valid as long as there is no evidence to dispute it. Therefore, theories can be disproven. Basically, if evidence accumulates to support a hypothesis, then the hypothesis can become accepted as a good explanation of a phenomenon. One definition of a theory is to say it's an accepted hypothesis.

Example: It is known that on June 30, 1908 in Tunguska, Siberia, there was an explosion equivalent to the detonation of about 15 million tons of TNT. Many hypotheses have been proposed for what caused the explosion. It is theorized that the explosion was caused by a natural extraterrestrial phenomenon, and was not caused by man. Is this theory a fact? No. The event is a recorded fact. Is this this theory generally accepted to be true, based on evidence to-date? Yes. Can this theory be shown to be false and be discarded? Yes.

What about the Law?

A law generalizes a body of observations. At the time it is made, no exceptions have been found to a law. Scientific laws describe things, but they do not explain them. One way to tell a law and a theory apart is to ask if the description gives you a means to explain 'why'.

Example: Consider Newton's Law of Gravity. Newton could use this law to predict the behavior of a dropped object, but he couldn't explain why it happened.

-Scientific Hypothesis, Theory, Law Definitions