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Theory: a well-substantiated explanation of some aspect of the natural world; an organized system of accepted knowledge that applies in a variety of circumstances to explain a specific set of phenomena; "theories can incorporate facts and laws and tested hypotheses." Addendum: "Theories do not grow up to be laws. Theories explain laws." (Courtesy of VadeRetro.)

This does not square with what other scientists believe:

It is extremely important to distinguish between facts and theories in science, and in every other subject also, because facts usually remain the same and theories often change. They are not always easy to differentiate, and even scientists forget to do it. And the people who write science text books nearly always forget to do it. So I'll try to give you some guidelines so you can do it yourself, because twenty years from now the facts will be the same, but the theories may have changed a lot. I know because I've had to relearn some theories since I taught this class 25 years ago, but the facts are the same. For example, the universe has doubled in age since I was a boy,which gives you an idea of just how old I am. In this class, we will try to spend about 2/3 of the time on facts, so that you won't need to relearn the entire class when the theories change. Of course, we can't ignore the theories altogether, because they are our best explanations of the facts; it's just that we shouldn't consider them to be absolute truth. When some people see a scientific theory disproven and replaced by another, they lose confidence in all of science, which is a big mistake. That is how science progresses, and it is a wonderful way to learn about our world. So let's begin by reviewing the scientific method, to see just how facts and theories interact. - John Pratt, Fact or Theory

I know because I've had to relearn some theories since I taught this class 25 years ago, but the facts are the same. For example, the universe has doubled in age since I was a boy,which gives you an idea of just how old I am.

That's a really strange quote, and a fairly worthless one. I wouldn't repeat it. It starts off OK, but then when the author goes to give an example of a theory that has changed, he says, "the age of the universe has doubled".

"The age of the universe" is not a theory. It is a fact: it is a physical property of the universe that we measure. It may be possible to derive a prediction of the age of the universe from a theory, but that's not what is done: we calculate it from a series of physical measurements.

"But in order to calculate, you need a theory!" you say. Perhaps, but those aspects of the theory (e.g. how light propagates through the universe, and how stars and supernovae work) haven't changed very much, while the measurements and measurement techniques have. The age of the universe is no more a theory than the length of your foot is a theory.

If anything, his example stands as a counterexample of his assertion that facts remain the same.

Now, you may argue that the "fact" is the true age of the universe, and that that hasn't changed (much), even if our measurement has changed. But when it comes to physical properties, measurements are all science ever has to work with. And yes, they change.