Faith and Mythology: How do we decide something's a myth?

How do we decide something is a myth?

• Perhaps if it's provably false? But how is that different from any other kind of fiction.
• Deceptively false then? Not that anyone expects us to believe in the gods of Mount Olympus these days, but maybe people were expected to believe when the stories were first written down.
• Perhaps the story's just too convenient? Too unlikely? Of it doesn’t ring true to someone who has the right sort of knowledge (a neurosurgeon, for example, reading that internet email about the girl whose brother needs brain surgery).

So, what if your son phones home after a psychology class to accuse you of only believing “that Bible stuff” because it’s the cultural myth you grew up with. It sounds kind of arrogant—I’m intelligent enough to recognize a myth when I see one—but he probably means well. He thinks you’re intelligent too. That’s why he’s asking. So what answers would you give? D'you think these would work (whatever that means)?

• Lots of people convert to Christianity? Yes, but they convert from it too.
• There’s got to be a reason Christianity spread round the world. Okay, but Islam's spreading too.
• Jesus is a real historical person. But that doesn’t prove he’s God.
• I know the Bible’s true. But my non-Christian neighbor is just as convinced it’s not.
• The stories don’t sound like myths. That’s because I’m looking for evidence that they’re not. Other people’s stories may not sound like myths if they interpret them right either.

You'll probably end up trying to define how the Bible's different from myths, so, more next time...