"How would you then define someone who lacks belief in deities for lack of sufficient evidence, but stops short of saying "deities do not exist"? Do you have a term for that?
I think you can't put lack and reason together. I think the correct would be denial and reason.
If you don't care about the reason (why I don't have a vagina; why I'm not an Asian; why I was not born in the 19th century; etc..) you can say you lack the motivation to even question these "no" realities.
But if you want to find a reason so you must be in denial of these realities.
Also the evidence issue again. What kind of evidence someone who lacks something would even care about?
Idk but I think defining atheism as a "lack" would bring a problem of epistemology.
When such problems arise usually a method is used to test its contingency.
For example, sex exists without rape. But rape doesn't exists without sex. So rape is contingent to sex. Rape doesn't exist by itself.
If you apply this logic to theism and atheism you'll easily notice that atheism needs the existence of theism. It doesn't exists by itself. So it's very strange the "lack" definition. I think the "denial" definition makes more sense.
"Lack" imply an "I don't care" attitude.
New atheism is much better defined as denial. Probabilistic denial because they say there's PROBABLY no God.