The ability to prove or disprove a theory is one of the strongest part of scientific theory. To prove a theory correct you should be testing it to try to make it fail.
The theory of gravity would be tested to try to make it fail, under a wide variety of conditions. Because if you dont try to disprove it, someone else will. And if it is false, then you would be made a fool
Creationism or ID can not be proven positive or false. Evolution can be proven on a small scale, and through observation a large scale.