That's really kind of interesting, Thal. One would think that a scientist wouldn't choose a side until there was either 100% scientific proof supporting intelligent design or 100% scientific proof supporting that no intelligence could possibly have designed the universe.
There isn't 100% proof in *anything* scientific. That's part of having a scientific theory -- in order to be scientific it must always be able to be disproven -- if a theory cannot be proven wrong, it isn't a scientific theory. If scientists ever believed that something was 100% correct and couldn't not be proven wrong and there was no room for doubt, that would be practicing faith and not science.
That doesn't mean that science is wishy-washy, though. Fuzzy math is more useful for understanding scientific theories than black/white true/false binary logic. Outside o the quantum regieme, gravity is thought to be well understood. So is electromagnetism. The big bang theory is nearly on as stable of footing, but with some details like inflation not being entirely nailed down. The ability of string theory to enlighten us about quantum gravity is on very shaky ground (although it is clearly mathematics, and useful to study).
There is some room to doubt, though. Given the problems with dark matter, one solution to that problem is that we don't actually understand gravity on the scale of galaxies and galaxy clusters (dark matter in that case doesn't exist, but gravity changes). That explanation has tended to loose favor, but if we get better measurements that alternative explanations cannot account for all the dark matter, then modifications to Einstein's General Relativity is back on the table.
Am I incorrect in thinking that the definition of an agnostic is one who doesn't know if God exists or or does not exist?
Wouldn't a scientist believe in his theory about the existence or lack of existence of God, gods, intelligent design, etc., but keep an open mind that his theory might be wrong?
I don't think anyone has provided scientific proof of either.
An awful lot of scientists apply Occam's razor to God and self-identify as atheists. What they're stating is just that they feel it 99% likely that God does not exist, even if there is no scientific proof, and they feel the burden of proof is on providing the proof that God exists[*].
[*] And for the religious people reading this, I'm not arguing that you have to entertain this viewpoint, but that a lot of scientists entertain this viewpoint.