Because I didn't read the book, after the film was over, in the back of my mind I never considered the second story even for a second!    I thought he was just making it up, but at that point I was a little perplexed when the writer revealed that the characters in his second story mirrored the animals in his 'real' story. I even brushed off comments when I was first coming across that said the second story could be real.

So now you know what story I believe in... but thanks to the 'hard cold facts' of the second story that were being put forth, I was somewhat being forced to rethink about what exactly happened to Pi. Do I believe in the second story?

IF one truly believed in the first story, no amount of hard facts can ever change you. How likely you are to just switch 'beliefs' shows how strong of a believer you are in either one of your beliefs. The same goes with the believe / faith in God...

You can bring in as many possibilities or proof that the second story is real, but as I have said before, if you are a strong believer in the first story, no amount of 'evidence' will change you.

If you believe...
Animal story = A life of myth, beliefs and religion. Godly.
Human story = Harsh cold facts of life and more grounded in 'science facts' in the realm of possibilities. Less Godly.
Both = As Pi's father himself said, believing in everything is akin to not believing in anything at all

Doubt anyone would not believe in either story, if not there's no point of even being given a choice. Everyone makes choices in life.