What is Atheism?

[Nonpareil]

No one says that the proposition "God does not exist" has no truth value. They say that it has an unknown truth value, as does "God exists", and that lack of belief is all that is required to be labeled an atheist.

That's all well and good except if that is your position then you have no right to say whether someone should or should not be theist, including yourself.

No.

Let us say, for the sake of argument, that "God exists" has an entirely unknown truth value. There is no evidence one way or the other.

Being a theist is still illogical and irrational.

When someone says "I am not a theist because of insufficient evidence"  he or she is tacitly admitting that one should prefer one epistemological position over another.

Well, yes. Because "God does not exist" is the null hypothesis. Absent any evidence that God exists, you should prefer that. That's what the null hypothesis is for.

I do not believe atheists can sufficiently justify disbelief as the better default position since (as I've argued elsewhere  A Better Default   ) our instincts, common experience and thousands of years of cross cultural reports point us in the direction of God's existence.

Instincts and cultural beliefs mean nothing if you have no actual evidence to back them up.

Actually that's kind of funny. I think I just argued that atheists have a burden of proof to show that people should have an epistemological preference for disbelief.

Yes.

It's called skepticism and the null hypothesis.