Dr. Tony has an excellent post on the processes of science, discussing some words like “theory” and “fact” and also talking about how one goes about doing science. This is from a general perspective, not just from biology or evolutionary theory.
One of my favorite books on Evolution, What Evolution Is by Ernst Mayr, seems to blur this point badly by using the terms “fact” and “theory” more in the popular sense. This makes trouble for all of us, I think, though obviously Mayr is a guiding scientific light:
“. . . Eventually it was widely appreciated that the occurrence of evolution was supported by such an overwhelming amount of evidence that it could no longer be called a theory. Indeed, since it was as well supported by facts as was heliocentricity, evolution also had to be considered a fact, like heliocentricity. . . .” (p. 12)
It’s troubling that a biologist of his stature uses that loose of definitions. Otherwise, his book is excellent, and I heartily recommend it. But I’m sticking with this: “Theories don’t grow up to be facts. They explain facts, and they grow up to be more firmly confirmed theories.”
I like the practical way in which Dr. Tony explains the process. Besides the meaning of “theory” he addresses the “science is what happens in the lab” error common in creationist circles. They announce that evolution cannot be science, because not every aspect can be repeated in a laboratory. His presentation deals nicely with that.