No offense to Holly, but you simply can't reason with a person that's convinced. A convinced person tries to find a way to feel comfortable with their convictions. That's how Young Earthers can manage to find solace in their beliefs with the occassional 'petrified boot' or whatever that they come across. "Ah, here it is! The proof that I'm on the right path." Throw three thousand bits of counter-evidence into the mix, and it will still be that one oddity that sticks out and allows them to believe whatever they have chosen to believe.
My father-in-law is the same way. No amount of reasoning will penetrate the fog of conviction.
(I keep saying "they", as if I'm not in that category. I shudder to think of all the things I'm unknowingly "convinced" of...)
Dave