Because the probability of there being a myth about Zeus, given that Zeus exists, is orders of magnitude higher than the probability of there being a myth about Zeus, given that he does not exist?
This seems obviously empirically false. Pick something that everyone agrees is made up- there are way more stories about cthulu than there are stories about any random person who happens to exist.
One of my kids more readily knows Paul Bunyan and John Henry than any US president. The fiction section of the library is substantially larger than the non-fiction. Probability that A exists, given that A is in a story seems very, very small.
This seems obviously empirically false. Pick something that everyone agrees is made up- there are way more stories about cthulu than there are stories about any random person who happens to exist.
One of my kids more readily knows Paul Bunyan and John Henry than any US president. The fiction section of the library is substantially larger than the non-fiction. Probability that A exists, given that A is in a story seems very, very small.