Most personally convincing reasons you don't believe.

[TheRocketSurgeon]

The lack of evidence should be every atheist's reason for not believing.

Frankly, for me the problem was the opposite. It was the presence of evidence of things my church had specifically told me literally could not be because of the Bible... or at least, our reliance of the literalism of the stories about talking donkeys and snakes, and the other magical thinking that comes from that worldview. I was already a sci-fi nut, and it wasn't much to really start enjoying my search into the details of and ways of knowing the actual nature of the universe. The evidence was everywhere! Turned out, everything I thought I knew was wrong, and it was not only obvious that the evidence for the claims of science were everywhere, it was testable-- and science actively taught you to question, to be skeptical, to not believe and to find out for yourself what is true and false.

Didn't take long before I realized, "Hey, not only can we test that science stuff to know if it's true or false, we can test this stuff, too!"

One, two, and a right hook. Down goes religion. Man spends next decade studying science. It makes me physically nauseated to hear a Christian try to tell me that they "reasoned" their way to Jesus after considering all the facts, and to listen to them butcher what I worked so hard to understand, and to know why we understand it is the way it is, into a caricature of pseudoscientific garbage they felt could muddy the waters with a, "yeah, well we may have talking demonic snakes and mud-man/rib-woman magic, but your stuff's not any better!"

Yeah. It is. And anyone who thinks the world was created in six days a few thousand years ago and then completely flooded is out of their minds. I'm so glad the memetic virus that is Christianity was purged by my brain's "skepticism immune system" before the virus destroyed my ability to realize I was no longer able to even approach objective thinking.

P.S. - To any non-insane Christians reading this, who have actual knowledge of history and science, and who isn't anti-intellectual (etc), I deeply apologize. I refer simply to the fundamentalists, the literalists who must believe in magical talking donkeys because they can't recognize a myth when they see one, and who reject science because they're really enamored with the idea of a mass-genocidal deity. These guys: