Pascal's Wager (the new version)

[EGross]

That works both ways. If a man claims to certainly know what is alleged to be beyond our knowledge, then he is a fraud.

Unless he knows it from a trusted source

If my wife tells me to do the dishes, I know her, see her, and I can confirm it is her, and I will do the dishes (I would have done them anyhow!)

If someone claims that God spke to him or her, how can such a person be trusted. If my wife told me that, even though I love here and trust her, I would not believe her simply because she has no idea what god looks like, sounds like, or whatever to verify it was god. I would most likely take her to a psychiatrist to handle her problem with hearing voices that are telling her to do things.

David Berkowitz heard his next door neighbor's dog tell him to do things, and he obeyed "Sam".

Since Islams believes in demons, how do you know that the trusted source is not pretending to be the good god? How do you know that the prophet is not just having a psychotic breakdown? In fact, you never met mohammed, and cannot make such a distinction. You can only rely on a tradition that God spoke to him, and you accept that.

That is belief, which requires a suspension of disbelief to maintain it.