Start out with a preconceived belief system, declare it to be fact, and therefore evolution has to be true.
I guess I don't know what you're talking about.
Creationism was the preconceived belief system, historically; but people more interested in evidence than in preconceptions found evidence that contradicted special creation and made a case for evolution.
Thus, evolution developed into the scientific consensus view, and creationism was relegated to surviving on dirty tricks and the gullibility of laypeople like yourself.
I'd dump a bunch of proof onto you, but I know the admins like things to stay on topic. I'll start a topic about that later on.
I look forward to it. Of course, it's a lot better to present the evidence than to simply assert that you have the ability do so but can't be bothered.
And there are many things that can't be explained by evolution, that's why there's still so much controversy.
There's actually no controversy. Just an extensive scientific consensus for evolution and laypeople with a limited grasp of the evidence and religious preconceptions.