I wanted to try something different in the post, so I have constructed some dialogue between three people discussing the existence of ghosts. What follows is based on actual conversations I have had; however, I have taken some license by collapsing multiple conversations along these lines into a single one to make it easier to read.
A: What about you? How many ghosts have you seen?The situation with gods is not much different, but there is at least one important difference that must be acknowledged if we are talking about the Christian god. At no point did the conversation above veer into the notion that ghosts have logically contradictory characteristics. Any discussion of the god in which Christians claim to believe is likely to include this important topic. The absence of evidence to support the existence of this god is undeniably important but so is the logical incoherence entailed by several of the characteristics this god is supposed to have.
B: I've seen four ghosts in my lifetime, each at a different time and in a different place.
Z: None of us have ever seen a ghost because ghosts don't exist.
A: How do you know what we've seen? Were you there?
Z: I don't claim to know what you saw. I have no idea what you saw, but I know it wasn't a ghost because ghosts don't exist.
A: How do you know they don't exist? You said you've never seen one. We have, and we know what we saw?
Z: I can be fairly confident that they do not exist because there has never been a single instance where evidence of a so-called ghost has been confirmed to the degree necessary for such an unusual phenomenon, and...
A: But you can't prove they don't exist!
Z: Let me finish. I am saying that ghosts do not exist because there has never been a single case where sufficient evidence was presented to support the extraordinary claim that ghosts are real. No conclusive video evidence, no instances of multiple observations made by reliable sources of the same sighting at the same time, etc. What I am saying is that we need impressive evidence to verify such a claim, and we have none. I certainly believe that many people think they have seen ghosts, but there is insufficient evidence to conclude that ghosts probably exist.
B: But like he said, you can't prove that ghosts don't exist.
Z: I think you are misunderstanding the meaning of "proof" in this context. You could argue that I can't prove that monsters don't live under your bed, but we both know they don't. To verify a knowledge claim, we examine the evidence supporting such a claim. We expect to find evidence in proportion to the likelihood of the claim being true, so we might not require much evidence for a rather ordinary or trivial claim. But for something like a colony of monsters living under your bed, we would require considerable evidence.
A: But this is different. I have evidence that ghosts exists because I saw one.
Z: Again, I believe that you think you saw a ghost. You might have even seen something that was not purely a product of your own mind. However, this is not the sort of evidence we need to verify the claim that ghosts exist.
