If you listen to The Atheist Experience show, or are involved in apologetics, you’ll find that one of the go-to arguments Christians rely on is “you can’t prove God doesn’t exist, therefore atheism is based on faith!”
The standard answer is that atheism is a lack of belief, not a belief that there is no God. This seems extremely difficult for Christians to understand, probably because they are stuck in the mindset that anyone who’s not a Christian must have some alternate religious worldview to compensate (and a lot of atheists are stuck in that mindset, too). This leads dialogues into one of two directions: either the Christian acknowledges the lack of belief in God and equates atheism with nihilism (because they confuse an apparent lack of worldview with an actual lack of worldview, which they equate with a conscious form of nihilism), or the Christian, due to their intellectual limitations, simply cannot understand how a lack of belief is different from a belief in the negative. Neither of these avenues are fruitful, and they both lead to frustration. This is partially why I think talking about atheism is a waste of time.
So the inevitable question posed to atheists is: “what is your proof that God does not exist?” To which atheists usually try to keep the high ground and reply that they only lack belief in God, and that it is the Christian who is making a statement about reality. The Christian is the one who has to prove that God exists. The atheist is free to disbelieve in anything that is not sufficiently justified, without having to prove anything in turn. So the atheist doesn’t have to prove anything, which is why it’s a good route to take if you’re having a dialogue.
But there is a difference between an expedient answer and an honest answer. Christians play fast and loose with the truth, and it’s hard to nail them down (pun intended). We have to resort to expedient answers in order to not get bogged down in details that just slow the conversation down.
The honest answer, I think, should be that there is no God. Of course there isn’t. We know the Christian god does not exist. We know the Greek gods don’t exist. There are no gods at the top of mountains, on the clouds, or in one of the ten to twenty-six dimensions that may or may not exist, all rolled up like an atomic swiss cake. To this people will inevitably reply, as Al Sharpton ill-advisedly tried to argue against Christopher Hitchens in their debate on the existence of God, what about the abstract concept “God”? Sharpton’s arguments failed, as these arguments always do, because there is no such thing as a “generic God” that is revealed to us by nature. The only concrete pieces of evidence we have for gods are holy books which proclaim the existence of a specific God, which can be easily disproven. These holy books are unconvincing, to say the least, but at least they are evidence. There is no evidence that someone like Sharpton can point to and say “look, here is a conception of God you can’t disprove!”
To continue along these lines, I think the perennial comparison with Santa Claus is never followed through, and that’s unfortunate. We don’t disbelieve in Santa Claus’ existence, we know Santa Claus does not exist. How do we know Santa Claus does not exist? The existence of Santa Claus is established through mythical narratives which don’t have much connection to reality. We also know that the concept of Santa Claus has evolved over time, from the Wild Man and Odin to Sinterklaas to the Santa Claus we know today. Like other myths, God’s existence is established through mythical narratives, such as the Bible or the Quran, and has evolved over time, from living and breathing pantheons to polytheism to highly abstract monotheism. Is this conclusive? It’s conclusive enough for us to declare Santa Claus, leprechauns, elves, fairies, and werewolves to be mythical creatures.
There are other strong arguments against the existence of God. The one I find most persuasive is the argument from physical minds. All the minds we know are the product of an evolutionary process and function on a material substrate, and we do not know of any minds which are not the product of evolution or which do not function on a material substrate. Therefore there is no reason to believe that such a mind could exist.