Truth?

Often I can't tell fiction from fact; I'm a literal person and fall for the most transparent lie.

I once blogged about my search for a definition of poetry.  I described a panel of performance poets that decided poetry is pretty much indefinable; they knew it when they heard it.  Well, now I'm trying to define fiction, and sometimes I don't know it when I read it.  That's because the range of western fiction stretches back to approximately 1500 BC or before, and has experienced so many permutations that definition becomes problematic.  Here's what I mean:

In The Odyssey, to begin at the beginning, Odysseus travels all around the western end of the Mediterranean Sea and has an enviable number of adventures.  Well, some of them are less than enviable, but you get what I mean.  I had to read The Odyssey in junior high school.  Sometime after that, I saw a documentary film that retraced Odysseus's journey and found, by god, the clashing rocks, an island of drug addicts who refuse to go home, and Circe's island, including her pigs and caves.  Result: I wonder whether there was a real Odysseus.  Sometimes I even wonder whether he didn't meet a temptress on one of those tiny Aegean islands and blame her for his dawdling an additional 10 years.

On the same track, we might also consider the stories compounded by Edgar Allan Poe's befuddled, alcoholic brain.  It could be argued that he merely recorded what he thought he saw.  And how about the stories used in the ever-popular political thriller, and written by former journalists?  Given the expensive craziness of the current political campaign, I would believe almost anything about any politician.  Of course, I mean that in the most respectful way imaginable.

I could go on and on, but I'm sure you get my point; there is a very fine, exceedingly blurred line between fact and fiction.  One of the inevitable questions posed to a writer is "where do you get your ideas?" Just suppose for a minute they didn't use ideas but memories...

I am currently plotting a thriller which will be titled A Murder of Crones.  It is based upon a reversal of that old, old myth of Oedipus, without the incest.  The idea occurred to me three or four years ago: how could an old woman recover her youth by getting a baby?  Then I and some friends watched helplessly as a crone of our acquaintance stole her grandson and got away with it. 
Is a story ever entirely truth or entirely fiction?  Which is which, and which came first?  This is not a chicken joke.