Evolution'ism'. is not a theory, no.
The Theory of Evolution is a theory, though.
If you read the message I was replying to, you will notice that TB wants to have his Biblically-based "explanations" of natural phenomena taught as science in public school science classrooms.
Of course, my point was that there can be "explanations" of all kinds, including the "explanation" that the Great Galactic Goat made everything the way we see it today.
The difference between Biblically-based "explanations", the Galactic Goat "explanation", and those of science is that only the scientific ones are based upon observation of nature, are falsifiable, and the observations are repeatable.