There's a Japanese theory that it's the porous nature of all the paper materials, there's a classical conditioning theory that people read on the shitter so all the books trigger a response, my science teacher room mate guessed it might have to do with a bacteria found in books or paper which releases a gaseous by-product which might induce pooping...
Hmm, for me its usually the moment I walk in the book store.
My brain won't stop pondering time and space. It seems to aspire to the questionings of a quantum physicist and I don't have the heart to tell it that 'our' actual mathematical ability is that of a high school sophomore
I have great faith in fools. My friends call it self-confidence.