Atheists. Am I to understand that if a spirit were to strike up a conversation with you?

ahtiests are crazy if they don't believe God talks to them

Yes. Unless other people could hear and or validate the existence of this "spirit" independent of me, how exactly could I rule out insanity or delusion? Mental illness IS the usual explanation for people hearing voices.

edit: you bias the question by asserting the voice of the conversation is an actual spirit. In reality though I'd just hear a voice and not really and truly know it was a spirit. So the real question is this: if you hear voices in your head, on what basis do you conclude that the conversation is with a spirit and not just your insanity or a delusion?

That would be a logical assumption to make. Although it would also be fair to think that a person seeing a spirit could judge whether their mental state is stable and make a correct call. As an atheist I think that if a 'real spirit' presented itself to me in a convincing way (not just shadows in a passage or a dream or something open to interpretation), then I'd be willing to change my viewpoint without thinking I'm insane. If spirits were a fact, then wouldn't the lack of belief in them be the true insanity?

Yes, I would willingly check myself into the nearest mental hospital.

That's about right yes, or he could punch me in the face and then I'd ask my friends if I had a bruise...

Even if others told me I would know it's a prank.

actually, youll never understand