10: The complete lack of solid evidence for God's existence.
This is probably the best argument I have against God's existence: There's no evidence for it. No good evidence, anyway. No evidence that doesn't just amount to opinion and tradition and confirmation bias and all the other stuff I've been talking about. No evidence that doesn't fall apart upon close examination.
And in a perfect world, that should have been the only argument I needed. In a perfect world, I shouldn't have had to spend a month and a half collating and summarizing the reasons I don't believe in God, any more than I would have for Zeus or Quetzalcoatl or the Flying Spaghetti Monster. As thousands of atheists before me have pointed out: It is not up to us to prove that God does not exist. It is up to theists to prove that he does.
In a comment on my blog, arensb made a point on this topic that was so insightful, I'm still smacking myself on the head for not having thought of it myself. I was writing about how believers get upset at atheists when we reject religion after hearing 876,363 bad arguments for it, and how believers react to this by saying, "But you haven't considered Argument #876,364! How can you be so close-minded?" And arensb said:
"If, in fact, it turns out that argument #876,364 is the one that will convince you, WTF didn't the apologists put it in the top 10?"
If there's an argument for religion that's convincing -- actually convincing, convincing by means of something other than authority, tradition, personal intuition, confirmation bias, fear and intimidation, wishful thinking, or some combination of the above -- wouldn't we all know about it?
Wouldn't it have spread like wildfire? Wouldn't it be the Meme of All Memes? I mean, we all saw that Simon's Cat video within about two weeks of it hitting the Internet. Don't you think that the Truly Excellent Argument for God's Existence would have spread even faster, and wider, than some silly cartoon cat video?
If the arguments for religion are so wonderful, why are they so unconvincing to anyone who doesn't already believe?
And why does God need arguments, anyway? Why does God need people to make his arguments for him? Why can't he just reveal his true self, clearly and unequivocally, and settle the question once and for all? If God existed, why wouldn't it just be obvious?
It is not up to atheists to prove that God does not exist. It is up to believers to prove that he does. And in the absence of any good, solid evidence or arguments in favor of God's existence -- and in the presence of a whole lot of solid arguments against it -- I will continue to be an atheist. God almost certainly does not exist, and it's completely reasonable to act as if he doesn't.