The definition of theory in science is as follows:
As used in science, a theory is an explanation or model based on observation, experimentation, and reasoning, especially one that has been tested and confirmed as a general principle helping to explain and predict natural phenomena.
Any scientific theory must be based on a careful and rational examination of the facts. A clear distinction needs to be made between facts (things which can be observed and/or measured) and theories (explanations which correlate and interpret the facts.
http://www.fsteiger.com/theory.htmlHere it is again:
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.
http://chemistry.about.com/od/chemistry101/a/lawtheory.htmNote that, as it pertains to science, science bases theories on "observation, experimentation, and reasoning" that a theory is something science has "tested and confirmed" and it helps to "explain and prediction natural phenomena." Scientific theories are not just guesses or ruminations, they have their basis in fact. Scientific theories have undergone repeated experimentation and pier review. This is the fundamental reason why "intelligent design" can NOT be a theory in the scientific sense. It's not "experimentable" or "observable." Intelligent design, i.e. creationism, is, in the popular sense, a "theory" because it is merely a guess.
Again, from Stephen Gould:
In the American vernacular, "theory" often means "imperfect fact"--part of a hierarchy of confidence running downhill from fact to theory to hypothesis to guess. Thus the power of the creationist argument: evolution is "only" a theory and intense debate now rages about many aspects of the theory. If evolution is worse than a fact, and scientists can't even make up their minds about the theory, then what confidence can we have in it? Indeed, President Reagan echoed this argument before an evangelical group in Dallas when he said (in what I devoutly hope was campaign rhetoric): "Well, it is a theory. It is a scientific theory only, and it has in recent years been challenged in the world of science--that is, not believed in the scientific community to be as infallible as it once was."
Well evolution is a theory. It is also a fact. And facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts. Facts don't go away when scientists debate rival theories to explain them. Einstein's theory of gravitation replaced Newton's in this century, but apples didn't suspend themselves in midair, pending the outcome. And humans evolved from ape-like ancestors whether they did so by Darwin's proposed mechanism or by some other yet to be discovered.
Moreover, "fact" doesn't mean "absolute certainty"; there ain't no such animal in an exciting and complex world. The final proofs of logic and mathematics flow deductively from stated premises and achieve certainty only because they are not about the empirical world. Evolutionists make no claim for perpetual truth, though creationists often do (and then attack us falsely for a style of argument that they themselves favor). In science "fact" can only mean "confirmed to such a degree that it would be perverse to withhold provisional consent." I suppose that apples might start to rise tomorrow, but the possibility does not merit equal time in physics classrooms.
Evolutionists have been very clear about this distinction of fact and theory from the very beginning, if only because we have always acknowledged how far we are from completely understanding the mechanisms (theory) by which evolution (fact) occurred. Darwin continually emphasized the difference between his two great and separate accomplishments: establishing the fact of evolution, and proposing a theory--natural selection--to explain the mechanism of evolution.
http://www.talkorigins.org/faqs/evolution-fact.html