Yes, I know. I can't prove to you that God exists. I'm terribly sorry. Is that what you wanted? Proof? Well, much like religion, we atheists do not deal in things like proof. Why, you ask? Not because like in religion's case, that it would destroy us... no, we have no proof simply because it cannot be.

What? I can't prove it? How dare I believe it?

Atheism, as it exists today, is not a belief system. It is merely the logical assumption that God does not exist. Logical. Yes. But I can't prove it. So? The fact of the matter is, that it is a rule of logic that any thing, such as God, flying purple bunnies, or a quality monkey wrench cannot be disproven. Cannot. At all. Why is that? Simple!

To prove something, you must provide evidence of its existence. The burden of proof lies upon the assertion of existence. To prove I have a dog, for example, is a simple matter - I would simply show you the dog. Reasonable enough an induction, to see a dog that I show you, and conclude I have a dog. To prove the existence of an object, you must simply display phenomena which can be best described by the existence of said object. To prove the sun exists, I can point to the burning ball in the sky, and note how it warms my skin. However, how would I go about proving I do not have a dog? Think on your own for a moment here. IMHO, short of possessing complete omniscience, I cannot prove such a thing. You might say, on a similar tangent, that you believe in God because you have never seen otherwise. Well, have you ever seen anything contradicting me owning a dog? Anything contradicting a pack of invisible transient rabid interplanar Teletubbies that follow you wherever you go? I certainly hope you do not assume every man you meet is Elvis, until you have reason to believe otherwise. You would be going about things backwards, my friend.

The key point here is that the claim of existence has consequences, and therefore holds the burden of proof. If I claim your sister is dead, there would be obvious consequences. The point becomes moot, and m_turner's argument succeeds, when there are no consequences either way: the question of whether or not A exists becomes irrelevant. The example below involving red and green describes this perfectly - since there are no consequences in the assertion of such a problem, the problem is irrelevant, and merely a good waste of your time. Claiming the existence of an omnipotent being responsible for all creation is a huge matter, and would likely have many far-reaching consequences. If you claim a God exists, but define Him as having no consequences toward the current understanding of the universe and having no observable characteristics, you have described a phenomenon which effectively does not exist. The definition of "exist" is "to have real being, material or spiritual" and to claim existence of an object which fails the definition is absurd.

No, I cannot prove to you the nonexistence of God. But I am equally helpless to disprove the existence of those pesky interplanar Teletubbies... absurd as it is. And this is why skepticism assumed the following rule:

Until you have reason to believe any given thing exists, you must assume its nonexistence.

Failure to abide by this simple rule will result in a mental trash-heap of absurd constructs. Thank you for your time.